Biocoating for Fertilizer Industry (SpringerBriefs in Applied Sciences and Technology) [1st ed. 2022] 9811960348, 9789811960345

Table of contents :
Introduction
Contents
1 Introduction to Biocoating
1.1 Background of Biocoating
1.2 Inorganic Coating and Biocoating
1.3 Problems in Fertilizer Coating
References
2 Biocoating from Composite Materials
2.1 Composite Material as Biocoating
2.1.1 Classification of Composite Materials
2.1.2 Characteristics of Composite Materials
2.1.3 Early Discovery of Composite Materials
2.1.4 Important Roles of Composite Materials in Twenty-First Century
2.1.5 Applications of Composites as Fertilizer’s Coating
2.1.6 Advantages and Disadvantages of Fertilizer Coating from Composites
2.2 Sodium Alginate as the Base of Biocoating
2.2.1 Water-Resistant Sodium Alginate Film
2.3 Fertilizer
2.4 Coating of Fertilizer
2.5 Common Techniques of Coating Fertilizers with Drying Process
References
3 Bacteria in Biocoating
3.1 Introduction
3.1.1 Classification of Bacteria
3.1.2 Staining and Identification of Bacteria
3.2 Bacillus subtilis
3.3 Applications of Bacteria in Composite
3.4 Applications of Bacteria in Fertilizer Industry
References
4 Evaluation of Biocoating
4.1 Properties of Films
4.1.1 Physical and Mechanical Analysis
4.1.2 Chemical Analysis
4.1.3 Microbial Analysis
4.2 Mechanism to Improve Conductivity by Integration of Bacteria and Metal Ions
4.2.1 Biosorption of Metal Ions
4.3 Mechanism to Retain Moisture Content Using Glycerol
4.4 Plant Growth Analysis
4.5 Soil Nutrients Analysis
4.6 Mathematical Modelling
References
5 Biocoating Evaluation Techniques
5.1 Growth Profile of Bacillus subtilis
5.2 Growth Kinetics of Bacillus subtilis
5.3 Culturing of Bacillus subtilis (Lag Phase, Log Phase, Stationary Phase)
5.4 Harvesting of Bacillus subtilis
5.5 Freeze-Drying of Bacillus subtilis
5.6 Preparation of Microbial Composite Films
5.7 Properties/Testing of Microbial Composite Films
5.7.1 Physical and Mechanical Properties of Microbial Composite Films
5.7.2 Chemical Analysis
5.7.3 Microbial Analysis
5.8 Conductivity and Moisture Content Improvement of Microbial Composite Films
5.8.1 Improving the Conductivity of Films
5.8.2 Improving the Moisture Content of Films
5.9 Fertilizer Coating
5.9.1 The 30-Min Drying Technique
5.9.2 The 24-h Drying Technique
5.10 Planting of Water Spinach
5.10.1 Plant Growth Analysis
5.10.2 Microbial Analysis of Microbial Composite Coated Fertilizers on Soils
5.10.3 Soil Nutrients Analysis
5.11 Microbial Analysis of Fertilizer Coated with Microbial Composite Film
5.12 Mathematical Modelling/Simulation
5.12.1 Mathematical Modelling/Simulation on Soil Nutrients Analysis
References
6 Conclusions

Citation preview

SpringerBriefs in Applied Sciences and Technology Husnul Azan Tajarudin · Charles Wai Chun Ng

Biocoating for  Fertilizer Industry

SpringerBriefs in Applied Sciences and Technology

SpringerBriefs present concise summaries of cutting-edge research and practical applications across a wide spectrum of fields. Featuring compact volumes of 50 to 125 pages, the series covers a range of content from professional to academic. Typical publications can be: • A timely report of state-of-the art methods • An introduction to or a manual for the application of mathematical or computer techniques • A bridge between new research results, as published in journal articles • A snapshot of a hot or emerging topic • An in-depth case study • A presentation of core concepts that students must understand in order to make independent contributions SpringerBriefs are characterized by fast, global electronic dissemination, standard publishing contracts, standardized manuscript preparation and formatting guidelines, and expedited production schedules. On the one hand, SpringerBriefs in Applied Sciences and Technology are devoted to the publication of fundamentals and applications within the different classical engineering disciplines as well as in interdisciplinary fields that recently emerged between these areas. On the other hand, as the boundary separating fundamental research and applied technology is more and more dissolving, this series is particularly open to trans-disciplinary topics between fundamental science and engineering. Indexed by EI-Compendex, SCOPUS and Springerlink.

Husnul Azan Tajarudin · Charles Wai Chun Ng

Biocoating for Fertilizer Industry

Husnul Azan Tajarudin Division of Bioprocess Technology School of Industrial Technology Universiti Sains Malaysia Penang, Malaysia

Charles Wai Chun Ng Division of Bioprocess Technology School of Industrial Technology Universiti Sains Malaysia Penang, Malaysia

ISSN 2191-530X ISSN 2191-5318 (electronic) SpringerBriefs in Applied Sciences and Technology ISBN 978-981-19-6034-5 ISBN 978-981-19-6035-2 (eBook) https://doi.org/10.1007/978-981-19-6035-2 © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Introduction

This book presents the advancement of coating materials technology especially in agriculture, particularly for fertilizers. Fertilizers are a critical component in meeting rising demands and ensuring global food security. A new generation of fertilizers made by coating granules with biopolymers addresses these issues. Coating in agriculture is an important area in research for a more sustainable future. This book starts with explanations and in-depth reviews about the important terms such as composite material, sodium alginate, bacteria and Bacillus subtilis and then proceeds to the technical parts of the research which are, the properties of microbial composite films that included physical and mechanical properties, chemical properties, as well as the microbial analysis. Also in this book are topics such as fertilizer, coating of fertilizers, plant growth analysis, soil nutrients analysis and mathematical modelling. More importantly are the reviews on research gaps that are related to the novelty of this book, which is, that the fertilizer coating developed on this topic not only regulates the rate of fertilizer release but also contains helpful microbes that act as plant biocontrol agents and provides micronutrients to plants/crops. Also included in the book are reviews about the mechanisms involved, such as the mechanism to improve conductivity by integration of bacteria and metal ions and mechanism to retain moisture content using glycerol. Many examples and instances from existing research and related research gaps are discussed. It includes applications of composites as fertilizer’s coating, advantages and disadvantages of fertilizer coating from composites, applications of bacteria in composite, applications of bacteria in fertilizer industry as well as the common techniques of coating fertilizers with drying process.

v

Contents

1 Introduction to Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Background of Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Inorganic Coating and Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Problems in Fertilizer Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 3 5 6

2 Biocoating from Composite Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Composite Material as Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Classification of Composite Materials . . . . . . . . . . . . . . . . . . 2.1.2 Characteristics of Composite Materials . . . . . . . . . . . . . . . . . 2.1.3 Early Discovery of Composite Materials . . . . . . . . . . . . . . . 2.1.4 Important Roles of Composite Materials in Twenty-First Century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.5 Applications of Composites as Fertilizer’s Coating . . . . . . . 2.1.6 Advantages and Disadvantages of Fertilizer Coating from Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Sodium Alginate as the Base of Biocoating . . . . . . . . . . . . . . . . . . . . 2.2.1 Water-Resistant Sodium Alginate Film . . . . . . . . . . . . . . . . . 2.3 Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Coating of Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Common Techniques of Coating Fertilizers with Drying Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 9 10 10 11

3 Bacteria in Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Classification of Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Staining and Identification of Bacteria . . . . . . . . . . . . . . . . . 3.2 Bacillus subtilis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Applications of Bacteria in Composite . . . . . . . . . . . . . . . . . . . . . . . .

25 25 26 27 28 30

11 12 14 14 15 16 17 19 21

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Contents

3.4 Applications of Bacteria in Fertilizer Industry . . . . . . . . . . . . . . . . . . 30 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4 Evaluation of Biocoating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Properties of Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Physical and Mechanical Analysis . . . . . . . . . . . . . . . . . . . . . 4.1.2 Chemical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.3 Microbial Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Mechanism to Improve Conductivity by Integration of Bacteria and Metal Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Biosorption of Metal Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Mechanism to Retain Moisture Content Using Glycerol . . . . . . . . . 4.4 Plant Growth Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Soil Nutrients Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Mathematical Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35 35 36 38 39

5 Biocoating Evaluation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Growth Profile of Bacillus subtilis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Growth Kinetics of Bacillus subtilis . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Culturing of Bacillus subtilis (Lag Phase, Log Phase, Stationary Phase) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Harvesting of Bacillus subtilis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Freeze-Drying of Bacillus subtilis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Preparation of Microbial Composite Films . . . . . . . . . . . . . . . . . . . . . 5.7 Properties/Testing of Microbial Composite Films . . . . . . . . . . . . . . . 5.7.1 Physical and Mechanical Properties of Microbial Composite Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2 Chemical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.3 Microbial Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Conductivity and Moisture Content Improvement of Microbial Composite Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.1 Improving the Conductivity of Films . . . . . . . . . . . . . . . . . . 5.8.2 Improving the Moisture Content of Films . . . . . . . . . . . . . . . 5.9 Fertilizer Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.1 The 30-Min Drying Technique . . . . . . . . . . . . . . . . . . . . . . . . 5.9.2 The 24-h Drying Technique . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10 Planting of Water Spinach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.1 Plant Growth Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.2 Microbial Analysis of Microbial Composite Coated Fertilizers on Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.3 Soil Nutrients Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Microbial Analysis of Fertilizer Coated with Microbial Composite Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Mathematical Modelling/Simulation . . . . . . . . . . . . . . . . . . . . . . . . . .

47 47 48

39 41 42 43 43 44 45

48 49 50 50 51 51 59 59 60 60 62 62 63 63 63 64 66 66 68 69

Contents

ix

5.12.1 Mathematical Modelling/Simulation on Soil Nutrients Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Chapter 1

Introduction to Biocoating

1.1 Background of Biocoating Materials are the foundation for delivering human growth milestones and enhancing human lives and production standards. It plays a vital role in human civilization (Wai Chun et al. 2021; Firdaus et al. 2018). Human society will achieve new heights with enhanced production whenever a new epoch-making material is introduced. This reflects people’s ability to comprehend and modify nature through application of socially productive forces, science and technology. From Stone Age to the Iron Age and ultimately to current day, human society has encountered and used a variety of materials. This advancement rendered all materials identified as a markers of human civilization’s growth (Wang et al. 2011). Emerging technology is built on the basis of new materials. There are now more severe and accurate material criteria as a result of the rapid development of modern science and technology that focuses on industrial growth, economy and environmental protection (Ho et al. 2020). Material science is currently developing towards the development of materials that are manufactured according to specific qualities. High-performance composite materials were created to replace or strengthen most of the other materials available in the twentieth century for this purpose (Wang et al. 2011). The creation and growth of composite materials over the last few decades are one of the most impressive examples of material design in human history. Composite materials are multi-phase multi-component systems made up of matrix and reinforcing materials and divided into three phases: matrix, reinforcement and interphase (Jesson and Watts 2012). Materials Comprehensive Dictionary by Fazeli et al. (2019) provided a more specific and detailed description of composite materials: ‘Composite materials are new materials made up of several materials such as organic polymers, inorganic non-metal or metal and so on’ (Fazeli et al. 2019). Materials design may allow each component’s performance to balance and interact with one another, resulting in a new performance dominance with critical differences from mixed generic materials. It not only preserves the original product materials’ basic © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_1

1

2

1 Introduction to Biocoating

function but also produces outputs not represented by the integrated effects of the original components. Based on the notion, it is evident that composite materials are designable and their efficiency is determined by the relative content of composite materials, component relationships and configurations and phase type and layout. In industry, composite materials are typically created by combining two materials. The matrix or binder is one of the ingredients and reinforcement fillers are another. Although the two materials have quite distinct properties, they can be combined to create a composite with unique properties. Because the matrix and reinforcing components do not dissolve or mix, they may be easily differentiated within the composite. Sodium alginate was widely used as a matrix material. In the name of good film-forming characteristics, sodium alginate has the potential to be exploited as a source of edible or biodegradable films (Deepa et al. 2016). A coating is a layer of protective material that is applied to an object’s surface, often known as the substrate. The coating can be applied for aesthetic, functional or both purposes (Al-mohanna 2017). To manage fertilizer solubility in soil, a variety of coatings have been applied to the particles. Controlling the rate of nutrient release has a number of advantages in terms of the environment, economy and yield. Coated fertilizers provide a continuous supply of nutrients, which renders longer nutrient release and hence, lowers the cost involved. This could provide the plants with more uniform plant nutrition, greater development and increased performance in its growth. To date, a wide range of materials has been used as coatings on fertilizers (Shahid et al. 2020). Sodium alginate, as mentioned earlier, an environmentally friendly and biodegradable material, is an excellent substance to be used as coating for the fertilizer. A porous polymer film that attaches to microorganisms and retains them on a surface within a bioreactor, sensor or biocatalyst is known as a biocoating. Incorporating sodium alginate films with Bacillus subtilis is a good example of biocoating. Bacteria are noted for their small size structure, which is typically a few micrometres in length. Bacteria were among the first forms of life and the simplest organisms to evolve on earth and they can be found in every corner of the globe. Bacteria are the most common and ubiquitous life forms on earth and they play an important role in both productivity and the cycling of elements that are necessary for all other life forms (Al-mohanna 2017). Bacillus subtilis is a Gram-positive rod-shaped bacteria that can be found in soil, as well as in the gastrointestinal tracts of ruminants and humans. It’s a benign organism since it’s not pathogenic or toxic and it doesn’t have any features that cause disease in humans, animals or plants. The risk of this bacterium being used in fermentation facilities is extremely minimal. Bacillus subtilis has also been shown to have a major impact on the self-healing of concrete cracks (Shahid et al. 2020). Biocoatings on fertilizers, especially organic fertilizers have gained interest in recent years. A fertilizer is a natural or synthetic substance that contains chemical elements that aid the growth and productivity of plants. To meet the supply and demand, roughly 200 million tonnes of fertilizer are produced each year around the world. Nonetheless, due to inefficiency, a quarter of the fertilizers applied is lost to the environment. Slowing the release of nutrients from fertilizer can help to prevent

1.2 Inorganic Coating and Biocoating

3

inefficiency (Beig et al. 2020). Currently, there are many different types of fertilizers in the market. The two most common varieties are organic fertilizers and inorganic fertilizers. Composted organic materials and animal dung are examples of organic fertilizers that contain animal- or plant-based components that are either a byproduct or end product of naturally occurring processes (Wei et al. 2019). Inorganic fertilizers are chemical fertilizers that contain nutrient elements for the growth of crops made by chemical means. However, utilizing inorganic fertilizers has the effect of contaminating ground water and lowering soil productivity, both of which have had a long-term impact on crop output (Anisuzzaman et al. 2021), therefore organic fertilizers are preferred. Nevertheless organic fertilizers that are used without proper plan or management could lead to severe environmental issues as well as eutrophication that is polluting our lakes and rivers. Ergo, the technology of biocoating is used to coat the organic fertilizer to slow down its nutrients release rate so that the nutrients are released ideally at the rate that the plants use it. This could significantly reduce the occurrence of environmental issues. This book focuses on the utilization of Bacillus subtilis as the reinforcing material to fabricate microbial composite films as coating for fertilizer. Research was carried out to study the optimum conditions for the integration of sodium alginate with Bacillus subtilis in reinforcing the microbial composite films as fertilizer coating. Analyses performed include physical, mechanical, chemical and microbial properties. Experiments were then carried out to study the conductivity, moisture content and added micronutrients of microbial composite films for plants as supplements. This was followed by coating the fertilizer with sodium alginate coating and microbial composite film coating via different drying techniques. Subsequently, the plant growth analysis and soil nutrients analysis of plants by applying uncoated and coated fertilizers to the plants was evaluated. Finally, mathematical simulations were developed for soil nutrient analysis on the rate of fertilizer and micronutrient release to soil and plants.

1.2 Inorganic Coating and Biocoating The coating of fertilizers could be made from a variety of materials and each material provides different characteristics and functionalities. The two main categories of fertilizer coatings are inorganic and organic coatings. Sulphur-coated urea is an example of inorganic coated fertilizer. It is produced by coating molten sulphur on preheated urea granules (Rajan et al. 2021). Both organic and inorganic coatings are useful in creating slow release and controlled release of fertilizer. However, the contamination from the inorganic coating materials is often associated with environmental issues. The process of converting an inorganic pollutant is usually defined by a chemical reaction that results in a chemical change. This process will contaminate water, soil and air and pose a significant threat to human health and the environment. Inorganic contaminants are frequently introduced directly into water sources as a result of human activity and in this case, fertilizers coated with inorganic coatings.

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1 Introduction to Biocoating

On the other hand, biocoatings are another choice of coating for fertilizers. Biocoatings are referred to as biocatalytic latex nanocoatings, biocatalytic coatings, microbial paints and inks, latex copolymer films, synthetic biofilms, biomimetic leaves, cellular composite coatings and nanobiocomposites in the literature. One or more thin layers of metabolically active microorganisms are entrapped between partially-coalesced sticky insoluble latex or non-film-forming polymer particles to generate a biocoating (Lyngberg et al. 2001). The ratio between the size of the partially-coalesced polymer particles and the size of the cells, as well as the volume ratio of each particle type, are crucial to the biocoating microstructure, adhesion and porosity, according to Mota et al. (1999). When the volume ratio drops, the porosity reduces until it hits a minimum (about 70%), after which it begins to increase. Biocoatings can be applied to a wide range of low-cost, flexible materials, including polyester sheets, metals, porous materials, wood, paper, fibres, yarns and other nonwovens (Bernal et al. 2014). Biotechnology plays a critical role in reducing energy waste, preventing pollution, recycling gaseous carbon emissions and lowering global warming. As a result, researchers are looking for innovative composite materials that concentrate and stabilize bacteria as environmental biocatalysts in the biocoatings for rapid pollutant degradation, solar energy harvesting, carbon recycling, gas-cleaning and for other purposes to solve the environmental problems. Biocoatings encasing highly concentrated cell paste with little diffusion resistance sustain viable but non-growing microorganisms in thin (2–50 um), sticky, nanoporous, partially-coalesced, insoluble polymer coatings (Lyngberg et al. 2001). Colloid-based latex biocomposite adhesives can preserve the reactivity of desiccated vegetative cells, concentrate cells (500–1000-fold) to a very high-volume fraction (>50% by weight depending on cell size) and incorporate carbohydrate osmoprotectants to keep microbial membranes intact during controlled ambient drying (Flickinger et al. 2007). These cellular composites were found to be capable of fresh protein synthesis for thousands of hours after rehydration (Gosse et al. 2010). Biopolymers and biodegradable polymers are also used as biocoatings for the fertilizers. Biopolymers are recognized for being less expensive than synthetic polymers utilized as traditional coating materials, which are highly dependent on the extraction and purification procedures used (Yang et al. 2012). Other benefits of biopolymers include soil biodegradability and nontoxicity (Polman et al. 2021), good soil water-holding capacity, reduced oxidative stress, improved particle aggregation and less soil erosion. Biopolymers can also be employed as a soil amendment and to reactivate dormant microbial activity (Zhou et al. 2020). The biomass origins, extraction methods and chemical structures of biopolymers or biocoatings are crucial for selecting an appropriate biopolymer, which is determined by its availability, extraction and purification methods and a variety of fundamental physicochemical properties used in the creation of CRFs. The release lifetime of lignin, cellulose and starch-coated fertilizers has been found to be too short in several experiments (Yang et al. 2012). Due to the presence of hydroxyl groups (−OH) on their surfaces, cellulose and starch are hydrophilic polymers,

1.3 Problems in Fertilizer Coating

5

whereas starch has poor mechanical characteristics. Lignin is made up of heterogeneous biopolymers, is insoluble in water and is incompatible with highly crystalline hydrophilic polymers like chitin and cellulose (Ramli et al. 2015). Overcoming such limits is extremely important and here are some of the best ways to do so. Overcoming these restrictions is crucial and it is for this reason that biopolymers must undergo some chemical and physical alteration in order to be effective. Chitin, for example, can be deacetylated and converted into chitosan, which has excellent solubility and film-forming properties (Santos et al. n.d.). Crosslinkers, compatibilizers and plasticizers are frequently used in coating solutions by other researchers (Lum et al. 2013). The flexibility, tensile strength and adhesive properties of polymeric membranes are all affected by these additional components (Pe et al. 2007). Another example is the biocide-free waterborne latex binder emulsions. Latex paint binder emulsions are low-cost materials that can be designed to protect implanted cells from UV damage (Gosse et al. 2010). Latexes may be applied using high-speed industrial coating and printing processes and they provide a lot of flexibility in polymer design for tailored porosity, adherence (especially wet adhesion) and toxicity. The aqueous coating industry has researched polymer heterogeneity in latex coatings that contribute to film shape and adhesion after drying (Overbeek 2010). However, polymer emulsion chemists are only now beginning to investigate the complex molecular interactions between heterogeneous polymer particle surface chemistry, water, surfactants, viscosity modifiers, osmoprotectant carbohydrate and the complex surface of living cells during film formation and drying in order to alter coating functionality using biotechnology (Flickinger et al. 2017). Furthermore, because carbohydrates like sorbitol protect biological materials, their use in coating mixtures is expected to improve long-term stabilization and preservation of a variety of cells and biological components in biocoatings.

1.3 Problems in Fertilizer Coating Recently, most of the composites used for engineering applications of composite materials are inorganic. This is because organic composite materials are relatively less in strength and are not durable. These inorganic composites are not biodegradable and hardly decomposed even after a long period of time (Dufresne and Castaño 2017). The leftover non-biodegradable inorganic composites will cause adverse environmental impacts when the composite materials are disposed into the environment. Also, the production of these inorganic composites is highly dependent upon various kinds of chemical methods and processes. These methods not only require relatively high production costs but at the same time, due to the materials, chemicals and scientific approaches used, these methods also cause environmental pollution, safety and health problems (Seymour 1976). Therefore, bio-based materials such as bacteria have been chosen to reinforce and produce biological composites as an alternative to inorganic composites.

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Composites are normally made from a polymer matrix that is reinforced with an engineered, man-made, natural or other reinforcing material. The size of the reinforcing materials plays a crucial role in producing a high-quality composite film. In most cases, nanoscale reinforcing materials are preferable, but nanocomposites will in fact face processing difficulties and have not proven to be valuable, at least in an industrial context (Lau et al. 2009). Thus, bacteria of sub-micron size could be an alternative option for reinforcing composite films. In addition, the source of the renewable and abundantly available raw materials for the production of reinforcing materials is required to ensure quantity. Bacteria are a suitable source from this point of view because they can be easily found and cultivated in large quantities. This offers a win–win situation regarding the production of reinforcing materials for the production of composites. Environmental issues of fertilizers have been a continuous problem for decades. These environmental issues included climate change, waste problems and pollution especially water pollution. Water is a vital element for all life forms and is equally important to preserve environmental sustainability (Asharuddin et al. 2019; Talebi et al. 2020). One of the biggest reasons that cause water pollution is fertilizer runoff from agro-industry (FAO and IWMI 2017). The agriculture and food industries generate a significant portion of waste (Ng et al. 2020; Asharuddin et al. 2018). Therefore, fertilizers with organic coatings are needed to slow down and control the release rate of nutrients from the fertilizer. This could significantly reduce fertilizer runoff and hence help in curbing the environmental issues as sustainable material sources are an important agenda to protect the environment (Abobaker et al. 2022). Moreover, with better management of plantations with less pollution, it could secure our food sources and fight food crises globally. Conventional slow-release fertilizer coating such as coating made from sulphur could cause other environmental problems as well. It accounts for both air and water pollution (Brown 1982). Sulphur-coated fertilizers are expensive and the coating cracks easily due to its friability (Ibrahim et al. 2020). In addition, most of the conventional coated fertilizers focus only on fertilizer release rate. On that account, sodium alginate which is easily biodegradable and environmentally friendly plays an important role in this case. Moreover, with added beneficial bacterium that acts as both reinforcing material and biocontrol agent, the microbial sodium alginate coating could be the perfect alternative to current conventional fertilizer coating.

References M.S.A. Abobaker, H.A. Tajarudin, A.L. Ahmad, W.M. Wan Omar, C.N.W. Chun, Municipal landfill leachate treatment and sustainable ethanol production: a biogreen technology approach. Microorganisms 10(5), 880 (2022). https://doi.org/10.3390/microorganisms10050880 M.T. Al-mohanna, Bacterial introduction. Research Gate, April 2017, pp. 679–692 M. Anisuzzaman, M.Y. Rafii, N.M. Jaafar, S.I. Ramlee, M.F. Ikbal, M.A. Haque, Effect of organic and inorganic fertilizer on the growth and yield components of traditional and improved rice

References

7

(Oryzasativa l.) genotypes in malaysia. Agronomy 11(9), 1–22 (2021). https://doi.org/10.3390/ agronomy11091830 S.M. Asharuddin, N. Othman, N.S.M. Zin, H.A. Tajarudin, M.F. Md Din, Flocculation and antibacterial performance of dual coagulant system of modified cassava peel starch and alum. J. Water Process Eng. 31 (2019). https://doi.org/10.1016/j.jwpe.2019.100888 B. Beig, M.B.K. Niazi, Z. Jahan, A. Hussain, M.H. Zia, M.T. Mehran, Coating materials for slow release of nitrogen from urea fertilizer: a review. J. Plant Nutr. 43(10), 1510–1533 (2020). Taylor and Francis Inc. https://doi.org/10.1080/01904167.2020.1744647 O.I. Bernal, C.B. Mooney, M.C. Flickinger, Specific photosynthetic rate enhancement by cyanobacteria coated onto paper enables engineering of highly reactive cellular biocomposite “leaves.” Biotechnol. Bioeng. 111(10), 1993–2008 (2014). https://doi.org/10.1002/bit.25280 K.A. Brown, Sulphur in the environment: a review. Environ. Pollut. Ser. B Chem. Phys.3(1), 47–80 (1982). https://doi.org/10.1016/0143-148X(82)90042-8 B. Deepa, E. Abraham, L.A. Pothan, N. Cordeiro, M. Faria, S. Thomas, Biodegradable nanocomposite films based on sodium alginate and cellulose nanofibrils. Materials 9(1), 1–11 (2016). https://doi.org/10.3390/ma9010050 A. Dufresne, J. Castaño, Polysaccharide nanomaterial reinforced starch nanocomposites: a review. Starch/Staerke 69(1–2), 1–19 (2017). https://doi.org/10.1002/star.201500307 FAO, IWMI, Water Pollution From Agriculture: A Global Review. Executive Summary (Food and Agriculture Organization of the United Nations and the International Water Management Institute, 2017), p. 35 M. Fazeli, J.P. Florez, R.A. Simão, Improvement in adhesion of cellulose fibers to the thermoplastic starch matrix by plasma treatment modification. Compos. B Eng. 163, 207–216 (2019). https:// doi.org/10.1016/j.compositesb.2018.11.048 M.C. Flickinger, J.L. Schottel, D.R. Bond, A. Aksan, L.E. Scriven, Painting and printing living bacteria: engineering nanoporous biocatalytic coatings to preserve microbial viability and intensify reactivity. Biotechnol. Prog. 23(1), 2–17 (2007). https://doi.org/10.1021/bp060347r M.C. Flickinger, O.I. Bernal, M.J. Schulte, J.J. Broglie, C.J. Duran, A. Wallace, C.B. Mooney, O.D. Velev, Biocoatings: challenges to expanding the functionality of waterborne latex coatings by incorporating concentrated living microorganisms. J. Coat. Technol. Res. 14(4), 791–808 (2017). https://doi.org/10.1007/s11998-017-9933-6 J.L. Gosse, B.J. Engel, J.C.H. Hui, C.S. Harwood, M.C. Flickinger, Progress toward a biomimetic leaf: 4000 h of hydrogen production by coating-stabilized nongrowing photosynthetic Rhodopseudomonas palustris. Biotechnol. Prog. 26(4), 907–918 (2010). https://doi.org/ 10.1002/btpr.406 B.K.X. Ho, B. Azahari, M.F. bin Yhaya, A. Talebi, C.W.C. Ng, H.A. Tajarudin, N. Ismail, Green technology approach for reinforcement of calcium chloride cured sodium alginate films by isolated bacteria from palm oil mill effluent (Pome). Sustainability (Switzerland) 12(22), 1–13 (2020).https://doi.org/10.3390/su12229468 K.A. Ibrahim, M.Y. Naz, S. Shukrullah, S.A. Sulaiman, A. Ghaffar, N.M. AbdEl, Nitrogen pollution impact and remediation through low cost starch based biodegradable polymers. Sci. Rep. 10(1), 1–10 (2020). https://doi.org/10.1038/s41598-020-62793-3 D.A. Jesson, J.F. Watts, The interface and interphase in polymer matrix composites: effect on mechanical properties and methods for identification. Polym. Rev. 52(3–4), 321–354 (2012). https://doi.org/10.1080/15583724.2012.710288 A.K.T. Lau, D. Bhattacharyya, C.H.Y. Ling, Nanocomposites for engineering applications. J. Nanomater. 2009 (2009). https://doi.org/10.1155/2009/140586 Y.H. Lum, A. Shaaban, N.M.M. Mitan, M.F. Dimin, N. Mohamad, N. Hamid, S.M. Se, Characterization of urea encapsulated by biodegradable (2013).https://doi.org/10.1007/s10924-0120552-0 O.K. Lyngberg, C.P. Ng, V. Thiagarajan, L.E. Scriven, M.C. Flickinger, Engineering the microstructure and permeability of thin multilayer latex biocatalytic coatings containing E. Coli. Biotechnol. Prog. 17(6), 1169–1179 (2001). https://doi.org/10.1021/bp0100979

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S. MohdAsharuddin, N. Othman, N.S. Mohd Zin, H.A. Tajarudin, M.F. Md. Din, V. Kumar, Performance assessment of cassava peel starch and alum as dual coagulant for turbidity removal in dam water. Int. J. Integrated Eng. 10(4) (2018). https://doi.org/10.30880/ijie.2018.10.04.029 M. Mota, A. Teixeira, A. Yelshin, Different sizes. Science 15(4), 59–68 (1999) C.W.C. Ng, A.F. Ismail, M.M.Z. Makhtar, M.N.F. Jamaluddin, H.A. Tajarudin, Conversion of food waste via two-stage fermentation to controllable chicken feed nutrients by local isolated microorganism. Int. J. Recycl. Org. Waste Agric. 9(1), 33–47 (2020). https://doi.org/10.30486/ IJROWA.2020.671208 A. Overbeek, Polymer heterogeneity in waterborne coatings. J. Coat. Technol. Res. 7(1), 1–21 (2010). https://doi.org/10.1007/s11998-009-9201-5 S. Pe, E. Gonza, F. Flores-ce, Controlled release of ammonium nitrate from ethylcellulose coated formulations (2007), pp. 3304–3311 E.M.N. Polman, G.M. Gruter, J.R. Parsons, A. Tietema, Science of the total environment comparison of the aerobic biodegradation of biopolymers and the corresponding bioplastics: a review. Sci. Total Environ. 753, 141953 (2021). https://doi.org/10.1016/j.scitotenv.2020.141953 M. Rajan, S. Shahena, V. Chandran, L. Mathew, Controlled release of fertilizers—concept, reality, and mechanism, in Controlled Release Fertilizers for Sustainable Agriculture (Elsevier, 2021), pp. 41–56. https://doi.org/10.1016/b978-0-12-819555-0.00003-0 N.K. Ramli, N. Mansor, Z. Man, A comprehensive review on biodegradable polymers and their blends used in controlled- release fertilizer processes (2015). https://doi.org/10.1515/revce-20140021 V.P. Santos, S.S. Marques, C.S.V. Maia, M. Antonio, B. De Lima, L.D.O. Franco, Seafood waste as attractive source of chitin and chitosan production and their applications (n.d.) R.B. Seymour, The role of fillers and reinforcements in plastics technology, in Polymer-Plastics Technology and Engineering, vol. 7(1) (1976). https://doi.org/10.1080/03602557608063110 S. Shahid, M.A. Aslam, S. Ali, M. Zameer, Self-healing of cracks in concrete using bacillus strains encapsulated in sodium alginate beads (2020). 312–323. https://doi.org/10.1002/slct.201902206 A. Talebi, Y.S. Razali, N. Ismail, M. Rafatullah, H. Azan Tajarudin, Selective adsorption and recovery of volatile fatty acids from fermented landfill leachate by activated carbon process. Sci. Total Environ. 707 (2020). https://doi.org/10.1016/j.scitotenv.2019.134533 C.N. Wai Chun, H.A. Tajarudin, N. Ismail, B. Azahari, M. MohdZaini Makhtar, Elucidation of mechanical, physical, chemical and thermal properties of microbial composite films by integrating sodium alginate with Bacillus subtilis sp. Polymers 13(13) (2021). https://doi.org/10.3390/pol ym13132103 R.-M. Wang, S.-R. Zheng, Y.-P. Zheng, Introduction to polymer matrix composites, in Polymer Matrix Composites and Technology (2011), pp. 1–548. https://doi.org/10.1533/9780857092229.1 X. Wei, J. Chen, B. Gao, Z. Wang, Role of controlled and slow release fertilizers in fruit crop nutrition, in Fruit Crops: Diagnosis and Management of Nutrient Constraints, vol. 2014. (Elsevier Inc, 2019). https://doi.org/10.1016/B978-0-12-818732-6.00039-3 Y. Yang, M. Zhang, Y. Li, X. Fan, Y. Geng, Improving the quality of polymer-coated urea with recycled plastic, proper additives, and large tablets (2012) C. Zhou, P.S. So, X.W. Chen, A water retention model considering biopolymer-soil interactions. 586 (2020). https://doi.org/10.1016/j.jhydrol.2020.124874

Chapter 2

Biocoating from Composite Materials

2.1 Composite Material as Biocoating A composite material is a multi-phase combination material created by combining two or more component materials with different shapes and qualities (Jesson and Watts 2012). In addition to preserving the original component’s basic traits, the materials combine to create a new character that none of the original components had. The individual materials in the composite are easy to detect since they do not dissolve or mix together. Matrix phase, reinforcement phase and interphase are the three basic physical phases of composite materials (Wang et al. 2011). The type, composition, configuration, structure, interaction of these phases and relative content are the keys in determining the performance and quality of the composite materials. Composite materials’ matrix is composed of polymer matrix composites made up of diverse matrix components, metal matrix and non-metallic inorganic matrix. According to Zurale and Bhine (1998), fibrous materials such as organic fibre, glass fibre and others are commonly used as reinforcing materials (Zurale and Bhide 1998). Fibrous materials play the role in the composite material as the main load-bearing component, since the fibre modulus and fibre strength are far higher than the matrix content. However, Romanenko et al. (2012) stated that the properties of the matrix material will determine the characteristics of the composite materials (Romanenko et al. 2012). Any matrix materials with strong adhesion properties have to bind the reinforcing fibre tightly.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_2

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2.1.1 Classification of Composite Materials There are many different classifications of composite materials. The classification is based on the type of matrix material, the dispersed phase morphology and the type of reinforcing fibres used (Wang et al. 2011). Polymer matrix composites, metal matrix composites and inorganic non-metallic matrix composites are the types of composite materials classified according to the kind of matrix material, according to Rajak et al. (2019). The six types of classifications of composite materials based on the form of dispersed phase are—continuous fibre-reinforced composite materials, braid, fibrous fabric reinforced composite materials, sheet reinforced composite materials, whisker or short fibre reinforced composite materials, particle reinforced composite materials and nanoscale particle reinforced composite materials. Carbon fibre, glass fibre organic fibre, boron fibre, hybrid fibre and other types of reinforcing fibres were used to classify composite materials in some circumstances (Zurale and Bhide 1998). However, Wang et al. (2011) explained that composite materials can also be classified based on some different criteria (Wang et al. 2011). These include optical functional composite materials, thermal functional composite materials, electrical functional materials and other materials, depending on the purpose and function. They are classified as particle-strengthened composite materials, fibre-enhanced composite materials or composite materials strengthened by diffusion based on the reinforcing principle. There are also laminated composite materials, winding structural composites, textile structural composite materials and so on, depending on the preparation procedure. Furthermore, structural and functional composite materials are categorized according to their intended use.

2.1.2 Characteristics of Composite Materials The characteristics of composite materials can be distinctive in many ways, however, they should have the following characteristics. Firstly, the products can be microscopically non-homogeneous, with a distinct interface. Secondly, in terms of the initial performance, the component materials are different, but they can lead to enhanced performance for the composite materials produced (Wang et al. 2011). Other than this, there are also some common characteristics shared by different types of composite materials. First, the characteristic of the high specific modulus and specific strength. The specific modulus is the modulus-density ratio while the specific strength is the loaddensity ratio. For both the modulus and the intensity, the proportions or units are lengths. These characteristics are measures of the calculation of the rigidity and the bearing capacity of the material under the assumption of equal weight. Secondly, composite materials require a good resistance to fatigue and a high tolerance for

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damage. George et al. showed that the matrix-fibre interface can prevent crack propagation (George et al. 2001). Compared to the damage of traditional materials that instantaneously occurred due to unstable crack propagation, composite materials will develop a series of damage such as matrix cleavage, interfacial debonding and fibre breakage or splitting (Beaumont 1989). Composite materials also have multifunctional efficiency in various manufacturing techniques. Seymour was able to manufacture fibreglass reinforced plastics with good instantaneous temperature resistance, high-frequency dielectric properties and exceptional electrical insulation properties (Seymour 1976). Generally, composite content can be constructed depending on the condition and performance specifications of product. The manufacturing techniques, primarily moulding processes, can also be selected according to the form of fillers and matrix as well as the shape, size and product number (Wang et al. 2011). The flexibility of design of composite materials gives advantages in producing a product that is reliable, economical, safe and reasonable.

2.1.3 Early Discovery of Composite Materials The first modern composite material was glass fibre which is still commonly used in sporting equipment, vehicle bodies, boat hulls and concrete panels today. Glass fibre is made of plastic as matrix and glass as reinforcement. Nowadays, some advanced composites use carbon fibre instead of glass fibre, since carbon fibre is safer and lighter but needs higher manufacturing costs. These components are used in expensive sporting uniforms, especially golf clubs and aircraft frames. Composite technologies were first used in aerospace industry. Composite materials are primarily used in this industry on the adiabatic shell structures of solid rocket engine combustion chamber, liquid hydrogen tank structure, module structure of apparatus, missile inter-segment structure and various satellite structures. Similar to the aerospace industry, the use of composite materials in the aircraft industry is designed to reduce aircraft weight, which in turn reduces costs and improves aircraft performance (Maria 2013).

2.1.4 Important Roles of Composite Materials in Twenty-First Century The world’s growth pattern in twenty-first century is unpredictable at many extents as environmental problems are moving to a severe conditions. Raw materials are also facing shortages and severe depletion. These will undoubtedly give composite materials significant development roles and opportunities. Composite materials with

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distinctive features such as lightweight, high strength and noise reduction or insulation improve the quality of human life through numerous construction and transport applications, enhancing houses and transport tools’ comfort (Alberto 2013). Besides, composite materials also solve the problems of energy crisis and resource depletion (Wang et al. 2011). Products produced or strengthened with composite materials have also been proven to be lighter in weight, require less energy, are corrosion resistant and have a longer lifespan in terms of energy conservation. Composite goods can be used to replace raw materials or undeveloped resources in a variety of applications or product manufacturing, preventing resource depletion. There were composite materials produced from waste as environmental protection, using the waste and turning the harm to benefits, at the same time, creating green composite materials that could be easily biodegraded. This scenario could also be related as waste to wealth. As a result, composite materials are extensively used in industries such as construction, shipbuilding, automotive, electrical and electronic, spots, agriculture and fisheries, mechanical engineering, etc. (Wang et al. 2011). In present times, all these applications are becoming more prevalent, mainly because of the price and performance advantages of composite materials.

2.1.5 Applications of Composites as Fertilizer’s Coating Composites have a wide range of uses in our daily lives. The combination of strength and stiffness combined with lightweight is the main advantage of composite materials. Selecting a right blend of reinforcement and matrix material can produce properties that fit the needs of a specific construction with a specific function. Composites can be used to cover fertilizer, which is one of their many applications. The biodegradable polymer composites that contain poly (vinyl alcohol), horn meal, rapeseed cake, glycerol and phosphogypsum as coating materials for granular fertilizers are the first example of composites being used as fertilizer coatings. As a binder, poly (vinyl alcohol) was utilized. The other components, which accounted for roughly 70% of the composites’ bulk, were waste materials or by-products. This fertilizer contains plantfriendly nutrients such as phosphorus, nitrogen, calcium, potassium and sulphur. Fertilizers were encapsulated using the composites created. It was discovered that encapsulation increased the time it took for fertilizers to be released. Encapsulation also improved the fertilizer’s mechanical qualities. The fertilizer granules were covered with composite sheets and put to the test in tomato sprout culture. They had a significant positive impact on the development of the plant’s roots (Treinyte et al. 2018). Next example is the degradable slow-release fertilizer composite prepared by ex situ mixing of inverse vulcanized copolymer with urea. It is a slow-release urea composite fertilizer (SUCF) created by employing inverse vulcanized copolymer with enhanced biodegradation and nutrient release lifetime to improve crop production and nitrogen absorption efficacy. The leaching test demonstrated that after 16 days of incubation in distilled water, only 70% of the total nitrogen of SUCF

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made from 50% sulphur copolymer was released, however, after 20 days in soil, only 35% nitrogen was released. This shows that the composite coating exhibited good slow-release properties on the fertilizers (Manzoor Ghumman et al. 2022). The composite coating for fertilizer can also be produced from combination of epoxy resin (ER), bio-based polyurethane (BPU) and polyolefin wax (PW). The coatings include, firstly, the use of PW as a modified inner coating that improved fertilizer surface performance and reduces the urea surface roughness, secondly, the degradable BPU film is synthesized with liquefied starch (LS) as the outer coating material and thirdly, an epoxy resin protective layer that improves the hydrophobicity of the coated urea for controlled release. It is seen that PW increases the uniformity of urea heating by optimizing the fluidity, thermal insulating characteristics and microscopic surface of the particles. Also, the release period of the fertilizers was shown to be extended (Tian et al. 2019). Furthermore, composite from two comparable polyhedral oligomeric silsesquioxanes (POSS) with eight same vertex groups can also be used to fabricate bio-based polyurethane nanocomposite thin coating. This is done by two identical POSS, with eight poly (ethylene glycol) (PEG) and octaphenyl groups connected to the cage, were incorporated into thin castor oil-based polyurethane coatings via in-situ polymerization on the urea surface. The nanostructure coatings are safe for the environment, simple to make and have variable properties. It is shown that even with a low coating rate of 2 wt%, the vertex group of POSS has a significant impact on dispersion level and interaction between polyurethane and POSS, which fine-tuned the release pattern and time of coated urea. This is because the liquid POSS with long and flexible PEG groups has superior compatibility and dispersibility in polyurethane matrix than the solid POSS with rigid octaphenyl groups. The varying degrees of physical crosslinking also resulted in unique characteristics. Therefore, the addition of POSS to a bio-based polyurethane coating gave another way of slowing down the release of nutrients from the fertilizer (Li et al. 2021). Table 2.1 shows previous research using composite as fertilizer’s coating. Table 2.1 Previous research using composite as fertilizer’s coating Components of composite

References

Poly (vinyl alcohol), horn meal, rapeseed cake, glycerol and Treinyte et al. (2018) phosphogypsum Inverse vulcanized copolymer with urea

Manzoor Ghumman et al. (2022)

Epoxy resin (ER), bio-based polyurethane (BPU) and polyolefin wax (PW)

Tian et al. (2019)

Polyhedral oligomeric silsesquioxanes POSS with eight same vertex groups

Li et al. (2021)

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2.1.6 Advantages and Disadvantages of Fertilizer Coating from Composites Fertilizer coating can be made from different types of materials. It can be made from materials of single ingredient or composite materials. There are always pros and cons of using the aforementioned materials on its own. It all depends on the condition that the fertilizers will be used or other factors that have to be taken into account on choosing the right materials as fertilizer coating. However, with recent research and advancement of technology in fertilizer coating, composite coating is preferred in many ways as generally, composites are more durable and versatile compared to coatings made of single material (Trenkel and Impr. Point 44 2010). Table 2.2 shows the advantages and disadvantages of fertilizer coating from composites.

2.2 Sodium Alginate as the Base of Biocoating Sodium alginate is a potential biopolymer film or coating component because of its unique colloidal properties, which include thickening, stability, suspension, film formation, gel development and emulsion stabilization (Mikkelsen and Elgsaeter 1995). It is a colloidal hydrophilic carbohydrate derived from different types of brown algae (Phaeophyceae) with diluted alkali (Norajit et al. 2010). In molecular terms, it is composed of β-d-mannuronic acid units and α-l-guluronic acid units which are linked together by 1–4-linkages. Ikeda et al. (2000) stated that alginic acid is the only polysaccharide that naturally contains carboxylic groups in each residue and possesses various functional material capabilities in different industries (Ikeda et al. 2000). Table 2.2 The advantages and disadvantages of fertilizer coating from composites Advantages

Disadvantages

Composite coating is more resistant to chemicals

Composite coating cannot withstand very high temperatures

Composite coating mostly does not require post-treatment finishing efforts

Heat capacity of composite coating are poor and hence cannot be used in conditions of high heat

Composite materials are lighter than some typical materials Composite coating can withstand relatively well in harsh environments. This increases the lifespan and strength of the composite materials Most composite coating for fertilizers is biodegradable and environmentally friendly

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Fig. 2.1 Chemical structure of alginic acid. Retrieved from Rhim (2004). Physical and mechanical properties of water-resistant sodium alginate films

With its excellent properties, such as readily available, biocompatible, biodegradable, non-toxic and gel-forming properties, alginate has been extensively used in industry as an emulsifier, colloidal stabilizer, and non-toxic food additive, hydrogels or as films (Carneiro-da-Cunha et al. 2010). It was developed as a source for biodegradable or edible films considering the potential amount available as a natural resource as well as the reproducibility of alginic acid (Williams 1978; Parris and Coffin 1997; Pavlath et al. 1999). Sodium alginate was produced by first purified and precipitated to form alginic acid. Subsequently, sodium alginate was formed by combining alginic acid with sodium carbonate. Biodegradable or edible film made from sodium alginate has been used as packaging materials to replace conventional plastics in many fields. This was because the biodegradable film produced was colourless or translucent and when imparted with plasticizer had improved flexibility (Pavlath et al. 1999) (Fig. 2.1).

2.2.1 Water-Resistant Sodium Alginate Film Though edible films created from hydrocolloids like alginate yield exceptionally high-mechanical-strength and transparent films (Moon et al. 2011). The films display low water resistance owing to their hydrophilic nature (Guilbert et al. 1995). According to Yai (2008), the films have low water vapour barrier properties and will dissolve when in contact with water (Yai 2008). Therefore, researchers have designed water-resistant sodium alginate film to tackle this issue (Rhim 2004). The mixing of alginate and calcium chloride formed rigid and insoluble gels that produced films with improved properties (Pavlath et al. 1999). In most circumstances, however, the rapid gel formation of alginate with calcium ions jeopardizes smooth film casting (Bierhalz et al. 2020). Ingar Draget et al. (1990) suggested a method for the formation of a uniform gel through gradual release of calcium (Ingar Draget et al. 1990). While Kaletunc et al. (1990) suggested a technique to immerse the film in aqueous multivalent cation solutions to improve the gel strength (Kaletunc et al.

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Fig. 2.2 Chemical structure of calcium chloride. Retrieved from Rhim et al. (2003). Modification of Na-Alginate Films by CaCl 2 Treatment

Fig. 2.3 Crosslinking process of sodium alginate by using calcium chloride solution. Retrieved from Rhim et al. (2003). Modification of Na-Alginate Films by CaCl 2 Treatment. Figure 2, pp 217

1990). Pavlath et al. (1999) stated that the technique of film immersion substantially enhanced the water resistance capability of alginate films (Pavlath et al. 1999). To remove the alginate hydrophilic groups, it could be done by reacting the alginates with polyvalent metal ions and the water solubility properties of sodium alginate films can be reduced (Grant et al. 1973). Calcium ions from CaCl2 were the multivalent metal ion used in this research to crosslink the alginates to create a water-insoluble film (Fig. 2.2). According to Pavlath et al. (1999), water-resistant properties of alginate film can be enhanced by using CaCl2 by the crosslinking of calcium ions on the film (Pavlath et al. 1999). There are two approaches for the process of crosslinking. The first approach is done by immersing the alginate film in solution CaCl2 , while the second method uses mixing of CaCl2 with alginate during the film preparation process. It shows, however, that this latter approach does not significantly enhance the waterresistant properties of films (Rhim 2004). Therefore, the alginate films in this research were produced by using the preferable first method which is through the immersion of films in CaCl2 solution (Fig. 2.3).

2.3 Fertilizer Fertilizers are compounds that are used to increase the output of crops. These are used by farmers to increase agricultural productivity. Fertilizers usually contain the nutrients that plants require, such as nitrogen, potassium and phosphorus. Organic and inorganic fertilizers are the two main forms of fertilizers. Natural organic fertilizers

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are mineral sources that comprise substances obtained from plant or animal materials, such as fresh or dried plant material, animal dung and litter and agricultural byproducts. The quantity of nutrients in organic fertilizers varies greatly depending on the source material and quickly biodegradable materials are ideal nutrition suppliers. Animal dung and composted organic materials are examples of organic fertilizers that contain plant- or animal-based components that are either a by-product or end product of naturally occurring processes (Wei et al. 2019). Synthetic inorganic fertilizer is made up of minerals and synthetic chemicals. Petroleum is a common source of inorganic nitrogen. In most extent, synthetic fertilizers can cause a lot of environmental problems, but organic fertilizers can help in this case. It not only can reduce the requirement for synthetic fertilizers to be applied on a regular basis to maintain soil fertility. It also provides energy to soil microbes, which helps to promote soil structure and crop growth (Green 2015). Nevertheless, improper use of organic fertilizers may result in overfertilization or nutritional deficiency in the soil. As a result, a controlled release of organic fertilizers is an effective and advanced strategy for reducing these effects while also ensuring long-term agricultural production (Shaji et al. 2021). Coating is one of the most effective ways to limit the release of nutrients into the soil solution, ensuring a nutritionally balanced environment for crop plant growth. Organic coating is chosen in the context of a sustainable environment since it is biodegradable and does not harm the environment.

2.4 Coating of Fertilizer Coatings are thin layers of a covering substance that are deposited or put on the surface of any object to form a protective barrier against the surface deterioration caused by its reaction with its environment. To manage fertilizer solubility in soil, a variety of coatings have been put to the fertilizers. Controlling the rate of nutrient release has several advantages in terms of the environment, economy and yield. Coatings on fertilizers have been made from a variety of materials. Inorganic compounds and organic polymers are the two most common types of coating materials. Sulphur, bentonite and phosphogypsum are examples of inorganic materials, while organic polymers include synthetic polymers like polyurethane, polyethylene, alkyd resin and others, as well as natural polymers like starch, chitosan, sodium alginate and cellulose (Trenkel and Impr. Point 44 2010). Furthermore, current research has also revealed that organic compounds such as charcoal, rosin and polyphenol are being used as coating (Wang et al. 2020a). Coatings are most typically employed on granular or prilled nitrogen (N) fertilizer, but multi-nutrient fertilizers are also used occasionally. The first extensively used fertilizer coating was elemental sulphur (S). It entailed spraying molten sulphur over fertilizers granules, then applying sealant wax to fill in any gaps or defects in the covering. Other coated fertilizers are created by reacting various resin-based polymers on the surface of the fertilizer granule. Another method is to combine low-permeability polyethylene polymers with highpermeability coatings. Different combinations of these materials were tested to see

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how they affected the rate of urea release and whether they might be used as coating materials for fertilizers (Lawrencia et al. 2021). Adding a coating on a fertilizer particle incurs an additional cost, hence coated fertilizers are more expensive than non-coated products. However, considering the lost nutrients from fertilizers to the environment that could cause huge loss and bring detrimental effects to the environment, adding coating to fertilizers could be considered a wise move. Add values to the coating as multifunctional coating would be one of the best measures to tackle this issue. To control the nutrient release rate for individual applications, the content of the fertilizer coating and thickness are carefully modified. The time it takes for specific fertilizers to release nutrients might range from a few days, a few weeks to many months, depending on the product label. Since nitrogen release from coated fertilizers is influenced by a variety of environmental factors, predicting the pattern of release under a wide range of soil and cropping situations is difficult. Many coated fertilizers, for example, release more quickly as moisture and soil temperature rise. Some products rely on microbial activity in the soil to release nutrients. Some coating materials are fragile and susceptible to abrasion and breaking in extreme conditions. However, patterns of the nutrients released could be studied by manipulating the factors in the experiments such as fixing some of the variables except for the condition of fertilizers. Coated fertilizers are used in many agricultural and horticultural applications. They provide a consistent supply of nutrients, which may offer a number of benefits. These include better growth, more uniform plant nutrition and improved plant performance by removing the need for multiple fertilizer applications, reduced labour and application costs by removing the need for multiple fertilizer applications, greater tolerance of seedlings to closely placed fertilizer and prolonged nutrient release that may provide more uniform plant nutrition, better growth and improved plant performance by removing the need for multiple fertilizer applications. Coated fertilizers provide the most benefit when the length of nutrient release is synchronized with the timings of plant nutrient uptake (Lawrencia et al. 2021). To fulfil the growing demand of global population for food, roughly 200 million tonnes of urea fertilizers are produced each year around the world as soil fertility can be improved by adding fertilizers. The largest users of nitrogenous urea fertilizers are developing countries, with nitrogen effectiveness ranging from 40 to 70%. However, due to its rapid release in the soil, a quarter of the urea applied to soils is lost to the environment. The rapid release of regular urea can be harmful to the environment because it causes fertilizer burn in the crop, contamination of groundwater from leaching and ammonia emission into the atmosphere. Nitrogen is necessary for plant development and growth, but plants are unable to receive 40–70% of the nitrogen released by urea due to its rapid release. Therefore, to address this issue, a polymer coating on regular fertilizer can be added to improve its efficiency while also lowering the rate of release in the soil. The slow-release technique is the most recent and advanced means of providing food to plants (Beig et al. 2020). Slowing the release of nutrients can help to reduce inefficiency. Encapsulation or coating is one method

2.5 Common Techniques of Coating Fertilizers with Drying Process

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for accomplishing this. Higher nutrient efficiency and synchrony with the continuing nitrogen needs of plants are made possible by coating.

2.5 Common Techniques of Coating Fertilizers with Drying Process Coatings for granular fertilizers can be applied in a variety of ways, including spraying a liquid, dipping into a liquid, precipitation from supercritical fluids or electrostatic deposition of a powder (Agrawal and Pandey 2015). Immersion and spraying a liquid onto the substrate are the most popular methods for coating fertilizers. Coating pans (rotary drums) or fluid bed coaters are often used for spraying (Naz and Sulaiman 2016). However, rotary drums are not suitable for more fragile granular fertilizers. Thus, immersion method is more suitable for most types of fertilizers and it is more versatile in this context. Coating a fertilizer simply aims to protect the fertilizers and slow down the release of nutrients from the fertilizers to the soil and plants. Trenkel defined the term release as the transfer of a chemical ingredient into a plant in usable form is known as release. While slow or delayed release means that the pace at which a nutrient is released from a fertilizer must be slower than when the nutrient is readily available for plant uptake (Trenkel and Impr. Point 44 2010). The two common techniques of coating fertilizers are immersion method and coating pan as mentioned. Immersion method is one of the most straightforward methods but it is also the most flexible method as it could be applied on almost all types of fertilizers. Immersion method was done by simply dipping the fertilizer into the polymer coating solution (Li et al. 2017). The solution binds to the surface of fertilizer granules and is then dried under ambient conditions or in an oven. Another common way for coating fertilizer grains with polymeric solutions is to use a coating pan. Spray the coating liquid on the surface of the beads that have already been placed in the spray zone. A hot air stream is used to evaporate the solvent and then dry the coated particles and the coating solution is sprayed using an air-atomizing spray nozzle in the drum’s centre. The coating process starts when the fertilizer granules come into contact with the spray and are coated with the coating solution, which is then dried. After a period of circulation, the granules may re-enter the spray zone and the coating and drying process is repeated. The granule residency time at the surface of the cascade bed determines the amount of solution received by a granule per trip through the spray zone. Simultaneous heat and mass exchanges between the coater pan and the inlet air stream, the spraying material and substrate, the rotational speed, dimensions, baffle configuration and number, bed humidity, pan loading and pan coater temperature are all factors that influence the quality and performance of a coating (Nguyen et al. 2021). Table 2.3 summarizes some of the coating techniques.

20 Table 2.3 Common coating techniques

2 Biocoating from Composite Materials Coating technique

References

Immersion

Sofyane et al. (2020)

Rotating pan

Zhang and Yang (2021)

Rotary drum coater

Vudjung and Saengsuwan (2018)

Spray dryer

Messa and Faez (2020)

In-situ polymerization

Olad et al. (2018)

Copolymerization

Kenawy et al. (2018)

Coating methods have an impact on coating quality, which is a critical component in controlling nutrient release behaviour. Because the fertilizer granules are dipped into the coating solution, they can be partially dissolved with immersion, especially for water-soluble fertilizers. Therefore, ensuring the fertilizers to be in a firmer condition can be a good way to avoid the fertilizers from dissolving in the solution. Also, if the solution is too viscous, the granules can adhere to one other and the coating is often damaged when they are separated after drying. Thus, the process of immersion should be rapid yet balanced and steady. The fertilizers should be handled in a gentle manner to minimize the mechanical damage and hence cause less harm to the coated layer. However, it is difficult to establish a uniform thickness for the coated layer for the entire fertilizer batch. The nutrient release rate is influenced by the lack of coating consistency and increasing product variability (Sahni and Chaudhuri 2012). Nonetheless, this could still be overcome if the coating process is being monitored closely. Moreover, aggressive granule movement should be avoided as it could cause a high level of mechanical stress on the coated fertilizers and might influence the coating quality and, consequently, the release behaviour via these coatings will be affected as well (Wu and Liu 2008). Fertilizer granules can be coated by one or several layers using the same coating solution (Cui et al. 2020). They can also be coated with two or three layers of different solutions and different coating processes (Li et al. 2018). The most frequent layers are single and double. The immersion technique is typically used to create numerous layers from the same solution. The granules are dipped in the same coating solution once, twice or numerous times. The fertilizer granule will be dried before recoating till the appropriate number of layers are reached. As the number of coatings grows, the average thickness of the coating layer rises. To compare the release rate of nutrients from the fertilizers, Messa et al. developed a single-coating NPK fertilizer. They discovered that the coating reduced the initial release rate of NPK where 100% of NPK was released in water from coated fertilizer within 2 h, but 100% was released in water from uncoated fertilizer in less than 20 min (Messa and Faez 2020). NPK granules with double coatings can also be made from different materials. The goal of using numerous layers for double layers with different coating solutions is to ensure multiple characteristics. The first layer serves as a physical barrier to prevent nutrients from being released, while the second layer serves as a superabsorbent entity capable of absorbing water and releasing it when the plant requires it. These are multipurpose fertilizers that are very beneficial in arid areas. Due to a more compact

References

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structure of the coating and reduced porosity, several layers enhance the coating thickness and decrease its porosity, as well as the release rate, when compared to a single coating (Jarosiewicz and Tomaszewska 2003).

References A.M. Agrawal, P. Pandey, Scale up of pan coating process using quality by design principles. J. Pharm. Sci. 104(11), 3589–3611 (2015). https://doi.org/10.1002/jps.24582 M. Alberto, Introduction of fibre-reinforced polymers—polymers and composites: concepts, properties and processes, in Fiber Reinforced Polymers—The Technology Applied for Concrete Repair, pp. 3–40 (2013). https://doi.org/10.5772/54629 P.W.R. Beaumont, The failure of fibre composites: an overview. J. Strain Anal. Eng. Des. 24(4), 189–205 (1989). https://doi.org/10.1243/03093247V244189 B. Beig, M.B.K. Niazi, Z. Jahan, A. Hussain, M.H. Zia, M.T. Mehran, Coating materials for slow release of nitrogen from urea fertilizer: a review. J. Plant Nutr. 43(10), 1510–1533 (2020). https:// doi.org/10.1080/01904167.2020.1744647 A.C.K. Bierhalz, M.A. da Silva, T.G. Kieckbusch, Fundamentals of two-dimensional films and membranes, in Biopolymer Membranes and Films (Elsevier Inc., 2020). https://doi.org/10.1016/ b978-0-12-818134-8.00002-x M.G. Carneiro-da-Cunha, M.A. Cerqueira, B.W.S. Souza, S. Carvalho, M.A.C. Quintas, J.A. Teixeira, A.A. Vicente, Physical and thermal properties of a chitosan/alginate nanolayered PET film. Carbohyd. Polym. 82(1), 153–159 (2010). https://doi.org/10.1016/j.carbpol.2010.04.043 Y. Cui, Y. Xiang, Y. Xu, J. Wei, Z. Zhang, L. Li, J. Li, Poly-acrylic acid grafted natural rubber for multi-coated slow release compound fertilizer: preparation, properties and slow-release characteristics. Int. J. Biol. Macromol. 146, 540–548 (2020). https://doi.org/10.1016/j.ijbiomac.2020. 01.051 J. George, M.S. Sreekala, S. Thomas, A review on interface modification and characterization of natural fiber reinforced plastic composites. Polym. Eng. Sci. 41(9), 1471–1485 (2001). https:// doi.org/10.1002/pen.10846 G.T. Grant, E.R. Morris, D.A. Rees, P.J.C. Smith, D. Thom, Biological interactions between polysaccharides and divalent cations: the egg-box model. FEBS Lett. 32(1), 195–198 (1973). https://doi. org/10.1016/0014-5793(73)80770-7 B.W. Green, Fertilizers in aquaculture, in Feed and Feeding Practices in Aquaculture (Elsevier Ltd., 2015). https://doi.org/10.1016/b978-0-08-100506-4.00002-7 S. Guilbert, N. Gontard, B. Cuq, Technology and applications of edible protective films. Packag. Technol. Sci. 8(6), 339–346 (1995). https://doi.org/10.1002/pts.2770080607 A. Ikeda, A. Takemura, H. Ono, Preparation of low-molecular weight alginic acid by acid hydrolysis. Carbohyd. Polym. 42(4), 421–425 (2000). https://doi.org/10.1016/S0144-8617(99)00183-6 K. Ingar Draget, K. Østgaard, O. Smidsrød, Homogeneous alginate gels: a technical approach. Carbohyd. Polym. 14(2), 159–178 (1990). https://doi.org/10.1016/0144-8617(90)90028-Q A. Jarosiewicz, M. Tomaszewska, Controlled-release NPK fertilizer encapsulated by polymeric membranes. J. Agric. Food Chem. 51(2), 413–417 (2003). https://doi.org/10.1021/jf020800o D.A. Jesson, J.F. Watts, The interface and interphase in polymer matrix composites: effect on mechanical properties and methods for identification. Polym. Rev. 52(3–4), 321–354 (2012). https://doi.org/10.1080/15583724.2012.710288 G. Kaletunc, A. Nussinovitch, M. Peleg, Alginate texturization of highly acid fruit pulps and juices. J. Food Sci. 55(6), 1759–1761 (1990). https://doi.org/10.1111/j.1365-2621.1990.tb03622.x E.R. Kenawy, M.M. Azaam, E.M. El-nshar, Preparation of carboxymethyl cellulose-g-poly (acrylamide)/montmorillonite superabsorbent composite as a slow-release urea fertilizer. Polym. Adv. Technol. 29(7), 2072–2079 (2018). https://doi.org/10.1002/pat.4315

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D. Lawrencia, S.K. Wong, D.Y.S. Low, B.H. Goh, J.K. Goh, U.R. Ruktanonchai, A. Soottitantawat, L.H. Lee, S.Y. Tang, Controlled release fertilizers: a review on coating materials and mechanism of release. Plants 10(2), 1–26 (2021). https://doi.org/10.3390/plants10020238 J. Li, M. Wang, D. She, Y. Zhao, Structural functionalization of industrial softwood kraft lignin for simple dip-coating of urea as highly efficient nitrogen fertilizer. Ind. Crops Prod. 109, 255–265 (2017). https://doi.org/10.1016/j.indcrop.2017.08.011 H. Li, L. Sui, Y. Niu, Preparation and properties of a double-coated slow-release urea fertilizer with poly (propylene carbonate), a sodium polyacrylate hydroscopicity resin and sodium alginate. ChemistrySelect 3(26), 7643–7647 (2018). https://doi.org/10.1002/slct.201800913 L. Li, M. Wang, X. Wu, W. Yi, Q. Xiao, Bio-based polyurethane nanocomposite thin coatings from two comparable POSS with eight same vertex groups for controlled release urea. Sci. Rep. 11(1) (2021). https://doi.org/10.1038/s41598-021-89254-9 A.S. Manzoor Ghumman, R. Shamsuddin, M.M. Nasef, C. Maucieri, O.U. Rehman, A.A. Rosman, M.I. Haziq, A. Abbasi, Degradable slow-release fertilizer composite prepared by ex situ mixing of inverse vulcanized copolymer with urea. Agronomy 12(1) (2022). https://doi.org/10.3390/agr onomy12010065 M. Maria, Advanced composite materials of the future in aerospace industry. Incas Bull. 5(3), 139–150 (2013). https://doi.org/10.13111/2066-8201.2013.5.3.14 L.L. Messa, R. Faez, Spray-dried chitosan/nanocellulose microparticles: synergistic effects for the sustained release of NPK fertilizer. Cellulose 27(17), 10077–10093 (2020). https://doi.org/10. 1007/s10570-020-03482-2 A. Mikkelsen, A. Elgsaeter, Density distribution of calcium-induced alginate gels. A numerical study. Biopolymers 36(1), 17–41 (1995). https://doi.org/10.1002/bip.360360104 R.J. Moon, A. Martini, J. Nairn, J. Simonsen, J. Youngblood, Cellulose nanomaterials review: structure, properties and nanocomposites. Chem. Soc. Rev. 40(7) (2011). https://doi.org/10.1039/ c0cs00108b M.Y. Naz, S.A. Sulaiman, Slow release coating remedy for nitrogen loss from conventional urea: a review. J. Controlled Release 225, 109–120 (2016). https://doi.org/10.1016/j.jconrel.2016.01.037 T.H. Nguyen, M.N.T. An, M. Alam, N. Tran, D.V. Trinh, Empirical scale-up model of pan-coating process for controlled-release urea fertilizer production. Part. Sci. Technol. 39(6), 773–780 (2021). https://doi.org/10.1080/02726351.2020.1841348 K. Norajit, K.M. Kim, G.H. Ryu, Comparative studies on the characterization and antioxidant properties of biodegradable alginate films containing ginseng extract. J. Food Eng. 98(3), 377–384 (2010). https://doi.org/10.1016/j.jfoodeng.2010.01.015 A. Olad, H. Zebhi, D. Salari, A. Mirmohseni, A. Reyhani Tabar, Slow-release NPK fertilizer encapsulated by carboxymethyl cellulose-based nanocomposite with the function of water retention in soil. Mater. Sci. Eng. C 90, 333–340 (2018). https://doi.org/10.1016/j.msec.2018.04.083 N. Parris, D.R. Coffin, Composition factors affecting the water vapor permeability and tensile properties of hydrophilic zein films. J. Agric. Food Chem. 45(5), 1596–1599 (1997). https://doi. org/10.1021/jf960809o A.E. Pavlath, C. Gossett, W. Camirand, G.H. Robertson, Ionomeric films of alginic acid. J. Food Sci. 64(1), 61–63 (1999). https://doi.org/10.1111/j.1365-2621.1999.tb09861.x D.K. Rajak, D.D. Pagar, P.L. Menezes, E. Linul, Fiber-reinforced polymer composites: manufacturing, properties, and applications. Polymers 11(10) (2019). https://doi.org/10.3390/polym1110 1667 J.-W Rhim, J.-H Kim, D.-H Kim, Modification of Na-Alginate Films by CaCl2 Treatment. Korean Food Sci. Technol. 35(2), 217–221, (2003) J.W. Rhim, Physical and mechanical properties of water resistant sodium alginate films. LWT Food Sci. Technol. 37(3), 323–330 (2004). https://doi.org/10.1016/j.lwt.2003.09.008 ´ etosławski, R. Dziembaj, D. Alejandro, A. A. Romanenko, V. Suslyaev, M. Molenda, M. Swi˛ Escárpita, D. Cárdenas, H. Elizalde, O. Probst, A. Radchenko, P. Radchenko, M. Žmindák, M. Dudinský, Composites and Their Properties, ed. by N. Hu (2012)

References

23

E. Sahni, B. Chaudhuri, Experimental and modeling approaches in characterizing coating uniformity in a pan coater: a literature review. Pharm. Dev Technol. 17(2), 134–147 (2012). https://doi.org/ 10.3109/10837450.2011.649852 R.B. Seymour, The role of fillers and reinforcements in plastics technology. Polym. Plast. Technol. Eng. 7(1) (1976). https://doi.org/10.1080/03602557608063110 H. Shaji, V. Chandran, L. Mathew, Organic fertilizers as a route to controlled release of nutrients, in Controlled Release Fertilizers for Sustainable Agriculture (Elsevier Inc., 2021). https://doi.org/ 10.1016/b978-0-12-819555-0.00013-3 A. Sofyane, E. Ablouh, M. Lahcini, A. Elmeziane, M. Khouloud, H. Kaddami, M. Raihane, Slowrelease fertilizers based on starch acetate/glycerol/polyvinyl alcohol biocomposites for sustained nutrient release. Mater. Today: Proc. 36, 74–81 (2020). https://doi.org/10.1016/j.matpr.2020. 05.319 H. Tian, Z. Liu, M. Zhang, Y. Guo, L. Zheng, Y.C. Li, Biobased polyurethane, epoxy resin, and polyolefin wax composite coating for controlled-release fertilizer. ACS Appl. Mater. Interfaces 11(5), 5380–5392 (2019). https://doi.org/10.1021/acsami.8b16030 J. Treinyte, V. Grazuleviciene, R. Paleckiene, J. Ostrauskaite, L. Cesoniene, Biodegradable polymer composites as coating materials for granular fertilizers. J. Polym. Environ. 26(2), 543–554 (2018). https://doi.org/10.1007/s10924-017-0973-x M.E. Trenkel, Impr. Point 44, Slow- and controlled-release and stabilized fertilizers: an option for enhancing nutrient use efficiency in agriculture (International Fertilizer Industry Association (IFA), 2010) C. Vudjung, S. Saengsuwan, Biodegradable IPN hydrogels based on pre-vulcanized natural rubber and cassava starch as coating membrane for environment-friendly slow-release urea fertilizer. J. Polym. Environ. 26(9), 3967–3980 (2018). https://doi.org/10.1007/s10924-018-1274-8 R.-M. Wang, S.-R. Zheng, Y.-P. Zheng, Introduction to polymer matrix composites, in Polymer Matrix Composites and Technology, pp. 1–548 (2011). https://doi.org/10.1533/9780857092229.1 Y. Wang, H. Guo, X. Wang, Z. Ma, X. Li, R. Li, Q. Li, R Wang, X Jia, Spout Fluidized Bed Assisted Preparation of Poly(tannic acid)-Coated Urea Fertilizer. ACS Omega, 5(2), 1127–1133 (2020a). https://doi.org/10.1021/acsomega.9b03310 X. Wei, J. Chen, B. Gao, Z. Wang, Role of controlled and slow release fertilizers in fruit crop nutrition, in Fruit Crops: Diagnosis and Management of Nutrient Constraints, vol. 2014 (Elsevier Inc., 2019). https://doi.org/10.1016/B978-0-12-818732-6.00039-3 S.K. Williams, Evaluation of a calcium alginate for use on beef cuts. 43, 292–296 (1978) L. Wu, M. Liu, Preparation and properties of chitosan-coated NPK compound fertilizer with controlled-release and water-retention. Carbohyd. Polym. 72(2), 240–247 (2008). https://doi. org/10.1016/j.carbpol.2007.08.020 H. Yai, Edible films and coatings: characteristics and properties. Int. Food Res. J. 15(3), 237–248 (2008) M. Zhang, J. Yang, Preparation and characterization of multifunctional slow release fertilizer coated with cellulose derivatives. Int. J. Polym. Mater. Polym. Biomater. 70(11), 774–781 (2021). https:// doi.org/10.1080/00914037.2020.1765352 M.M. Zurale, S.J. Bhide, Mech. Compos. Mater. 34(5), 463–472 (1998)

Chapter 3

Bacteria in Biocoating

3.1 Introduction Bacteria, singular bacterium or any of a group of microscopic single-celled creatures are found in vast quantities in almost every habitat on Earth. Bacteria are the most common of all species and they may be found anywhere from deep marine vents to deep beneath the Earth’s surface to human digestive tracts (Adam and Perner 2018) (Chukwuma et al. 2021). Woese et al. (1990) declared that there is approximately 5 × 1030 bacteria on Earth, forming a biomass that exceeds that of all animals and plants (Woese et al. 1990). Bacteria are single-cell organisms that lack a membrane-bound nucleus and certain internal features, making them the only ones with prokaryotic cell organization (Woese and Fox 1977). Bacteria may use certain inorganic chemicals and practically any organic component as food source as a group due to their incredibly diversified metabolic capabilities. Although some bacteria can cause disease in humans, animals and plants, the vast majority of them are harmless. In terms of biodiversity, illness, genetics and technology, studies of interactions between distinct species of bacteria aim to provide amazing insights into the processes of evolution and the history of life on Earth (Chun et al. 2021). Bacteria serve a significant role as beneficial ecological organisms whose metabolic activity is essential for the survival of higher life forms on Earth and without them, life on the planet would perish (Woese et al. 1990). Bacteria in the ecosystem help to ensure important processes such as cellulose degradation organic matter decomposition, nitrogen fixation and photosynthesis. Approximately half of the bacterial phyla can now be cultured in the laboratory and over 5000 distinct bacteria kinds have been identified (Woese et al. 1990). There are several thousands of bacteria that have not been identified, that await their proper identification. Figure 3.1 shows the basic structure of bacteria.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_3

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Fig. 3.1 Basic structure of bacteria

3.1.1 Classification of Bacteria Naming and classifying bacterial properties, aids in the identification of their diversity. Bacteria are classified using genetic methods or cell shape and metabolism. Genetic techniques such as DNA-based systems and 16S rRNA analysis have been used to determine the degree of interconnect between bacterial species in order to acquire essential information (Rosselli et al. 2016). Since genetic differentiation emphasizes evolutionary ties in bacteria, biochemical and physical traits are also important for their categorization and identification. In reality, bacteria are classified based on a variety of characteristics, including motility, cell morphologies, spore development, multicell aggregation structure and gram stain reactivity. According to Tortora et al. the morphological characteristics can be affected by environmental factors, including the colour and form of bacterial colonies, which are not always constant (Sousa et al. 2013). Bacteria can only be properly characterized when grown on a specific medium because the conditions of their growth influence the changes in their attributes. Bacteria will consume nutrients in the medium and begin to expand, growing from thousands to millions of cells to billions. A bacterial colony is a collection of visible bacterial cells that stems from a single bacterial cell. Diverse bacteria contribute to different colonies; some colonies are coloured, while others are shaped irregularly (Seleen and Stark 1943). Colony morphology is the study of the structure and shape of bacterial colonies and it is the initial stage in identifying and characterizing a bacterial culture. Size, colour, opacity, form, elevation and margin are common features used to consistently and accurately define colony morphology. Figure 3.2 shows the morphological characteristics of bacterial colonies.

3.1 Introduction

27

Fig. 3.2 Morphological characteristics of bacterial colony. Retrieved from: Brown and Alfred. Benson’s microbiological applications: laboratory manual in general microbiology, 8th Ed. Figure 47.4, pp 160

3.1.2 Staining and Identification of Bacteria The very first step in the identification of bacteria is the gram stain test that determines whether the bacterium is Gram-positive or Gram-negative. Gram-positive bacteria are those that keep their crystal violet colour after being washed with a decolorizing solution in a gram stain test (Gregersen 1978). Gram-positive bacteria stain violet due to a thick layer of peptidoglycan in their cell walls, which helps to preserve the crystal violet staining. Gram-negative bacteria, on the other hand, were coloured scarlet or crimson after washing with fuchsine or safranin (Gregersen 1978). This is due to a thinner peptidoglycan wall, which allows the crystal violet to escape during the decoloring process. Another factor is that the composition of bacterial cell walls varies. Gram-negative bacteria have an outer cell membrane that Gram-positive bacteria do not have. Crystal violet dye, on the other hand, is maintained in Grampositive bacteria due to the presence of a rich peptidoglycan coating. Gram-negative bacteria have more impermeable cell walls than Gram-positive bacteria, making them more immune to antibodies (Richmond and Sykes 1973). The outer membrane of Gram-negative bacteria comprises lipopolysaccharide and protein molecules. This bacterium has a wide range of applications, including commercial use, medical treatment and Swiss cheese production (Caplice and Fitzgerald 1999). Figure 3.3 shows the structural differences between Gram-positive and Gram-negative bacteria. Under microscopic view, bacteria normally exhibit one of the three basic structures which are bacilli, cocci and spirilla (Al-mohanna 2017). Cocci have an oval or spherical shape, bacilli have a rod shape and spirilla have a hard spiral structure. Certain bacterial organisms exhibit grouping or cellular organization traits on occasion. Cocci can be found in pairs, in groups of four (tetrads), in groups of eight (sarcina), grape-like clusters (staphylococci) and even chains (streptococci).

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Fig. 3.3 Structural differences between Gram-positive and Gram-negative bacteria. Retrieved from: Brown and Alfred. Benson’s microbiological applications: laboratory manual in general microbiology, 8th Ed

Fig. 3.4 Basic structures of bacteria species. Retrieved from: Brown and Alfred. Benson’s microbiological applications: laboratory manual in general microbiology, 8th Ed. Figure 6.6, pp 34

Some bacteria produce long, branched filaments or even erect structures that release spores that grow into new bacteria. Figure 3.4 shows the basic structures of bacteria species.

3.2 Bacillus subtilis B. subtilis is a Gram-positive, rod-shaped, catalase-positive bacteria. B. subtilis cells are rod-shaped and range in size from 4 to 10 μm (m) in length and 0.25 to 1.0 μm in diameter, with a cell volume of around 4.6 fL at stationary phase (Yu et al. 2014). It

3.2 Bacillus subtilis

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may develop an endospore, like other Bacillus species, to endure harsh environmental conditions such as temperature and desiccation. B. subtilis is a facultative anaerobe that was once thought to be an obligatory aerobe (Nakano and Zuber 1998). B. subtilis has a lot of flagella, which allows it to move swiftly in liquids. B. subtilis has been widely used as a model organism for laboratory investigations, particularly sporulation, which is a simplified example of cellular differentiation. B. subtilis was reviewed by the US FDA Centre for Veterinary Medicine and found to pose no safety concerns when used in direct-fed microbial products, so it has been approved for use as an animal feed ingredient under Sect. 36.14 ‘Direct-fed Microorganisms’ by the Association of American Feed Control Officials. Several feed additives containing viable B. subtilis spores, on the other hand, have been positively reviewed by the European Food Safety Authority for their safe use in animal production. Different authority organizations have also reviewed B. subtilis and compounds produced from it for their safe and beneficial use in food. In the early 1960s, the Food and Drug Administration (FDA) published an opinion letter recognizing various microorganism-derived compounds as generally recognized as safe (GRAS), including carbohydrase and protease enzymes from B. subtilis. The European Food Safety Authority has granted it ‘Qualified Presumption of Safety’ classification (Ricci et al. 2017). The opinions were based on the utilization of nonpathogenic and nontoxicogenic strains of the organisms, as well as existing good manufacturing methods. The FDA claims that enzymes derived from the B. subtilis strain were widely used in food prior to January 1, 1958 and that nontoxigenic and nonpathogenic B. subtilis strains are widely accessible and have been used safely in a range of culinary applications. This includes consuming Japanese fermented soybeans in the form of natto, which contains up to 108 live cells per gramme and is widely consumed in Japan. The fermented beans are known for their contribution to a healthy gut flora and vitamin K2 intake; natto has not been linked to any adverse outcomes with the presence of B. subtilis over its long history of widespread use. The natto product, as well as the B. subtilis natto that is its main component, has been authorized by the Japanese Ministry of Health, Labour and Welfare as effective for health preservation. In this research, B. subtilis has been chosen to be used as the reinforcing material because of its useful and vast applications in many areas. However, most of the studies focused mainly on one application at a time. Therefore, this research went into deeper findings on the versatility of this bacterium that it could be used as the reinforcing material to reinforce the strength or the films, physically, mechanically, chemically and microbially. More than that, it could also act as the element that aid in the manipulation of the conductivity of the films which would also bring effects to the soil environment. Also, it is an effective biocontrol agent to plants in fighting against harmful pathogens. By incorporating this bacterium into the film or coating that could bring a series of benefits to the applications desired, is the focus of this research to provide in-depth investigations and analyses.

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3.3 Applications of Bacteria in Composite Bacteria have long been used in a variety of everyday applications. Bacteria have been demonstrated to be incredibly valuable in a variety of applications, ranging from the food sector to waste management. Bacteria are also used in composite applications outside of the aforementioned domain. The bacterial cellulose is one of the most commonly used components of bacteria. Bacterial cellulose is a naturally occurring exopolysaccharide produced by bacteria that is extremely pure. It’s been investigated for a long time for a range of medicinal and non-medical purposes. Apart from its adhesive properties, bacterial cellulose also protects against UV radiation, maintains an aerobic environment, preserves moisture and protects against heavy metal stress. The development of a number of promising biomedical devices has recently been facilitated by the manufacture of BC-based composite scaffolds compounded with other materials such as nanoparticles and polymers. In a number of biomedical polymeric scaffolds, BCderived nanocrystals (BCNCs) and nanofibrils (BCNFs) have proven to be efficient reinforcing agents (Liu et al. 2020). Because of its versatility, variety of shapes and forms, biocompatibility, haemocompatibility, mechanical strength, microporosity, biodegradability and unique surface chemistry, this is critical for advancements in biological applications such as wound healing, tissue engineering, drug administration, tumour cell culture and cancer treatment (Rajwade et al. 2015). In addition, due to its unique liquid absorption and medication loading capabilities, BC can also be used to treat a variety of malignancies. For in vitro culture of cancer cells to replicate tumour microenvironments, BC-based scaffolds have been created and tested. The adhesion, proliferation, ingrowth and differentiation of cancer cells, notably breast and ovarian cancer cells, are all supported by these scaffolds. It is demonstrated that BC is highly alterable for medical purposes, with a focus on the use of BC composites in cancer treatment (Islam et al. 2021). Moreover, bacteria can also be used for reinforcing composites. Not limited to bacterial cellulose, but bacterial cell body as nano-sized material is also extremely useful as organic, biodegradable material as a reinforcing material. In most cases, reinforcing materials are preferred to be extremely small in sizes such as micron or nano-sized to increase the surface area for composite interaction. Bacteria naturally as sub-micron size is a very good alternative for other synthetically fabricated reinforcing materials. More importantly, bacteria, as natural bio-based materials are totally biodegradable and benign strain, are harmless to the environment.

3.4 Applications of Bacteria in Fertilizer Industry Bacteria can be exploited as a major source of biofertilizers. When applied to seed, plant surfaces or soil, biofertilizers are biological preparations containing living microorganisms, particularly bacteria, that support plant growth by increasing the

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supply of nutrients, increasing root biomass or root area and raising the plant’s nutrient uptake potential. Biofertilizers are also important components of organic farming, as they help to maintain soil fertility and sustainability over time. These potential biological fertilizers would play a critical role in soil production and sustainability, as well as environmental protection, as environmentally benign and cost-effective inputs for farmers. Biofertilizers are thus a viable option for farmers aiming to increase productivity per unit area (Elavarasi et al. 2020). In agriculture and forestry, rhizospheric bacteria are good examples of useful bacteria in fertilizer industry. Plant growth-promoting pathways are found in several rhizospheric bacterial strains and these bacteria can be used as biofertilizers to boost crop yields. The usage of fertilizers based on helpful microorganisms is becoming more popular as there is a need for environmentally acceptable farming methods (Malusá et al. 2012). Bacterial biofertilizers can improve plant growth through several mechanisms, including the synthesis of plant nutrients or phytohormones that can be absorbed by plants, the mobilization of soil compounds that can be used as nutrients by the plant, the protection of plants under stressful conditions, thereby counteracting the negative effects of stress or defence against plant pathogens, thereby reducing plant diseases or death. For many years, several plant growth-promoting rhizobacteria (PGPR) have been used as biofertilizers all over the world, helping to boost crop yields and soil fertility and so contributing to more sustainable agriculture and forestry (García-Fraile et al. 2015). Beneficial bacteria can also aid in the activation of nutrients and the promotion of wheat development when fertilizer administration is limited. The use of too many chemical fertilizers has presented a serious threat to soil quality and the ecology. Pesticides, fertilizers and other chemicals have been used for a long time and this has resulted in a surge in agricultural concerns. This results in soil compaction, salinization and disease aggravation, as well as an imbalance in the proportions of various nutrients, the destruction of organic matter in the soil and a loss in the structural integrity and characteristics of aggregates. Inoculation with plant-growthpromoting rhizobacteria (PGPR) has emerged as a viable technique for ecosystem recovery. In ecological and sustainable agriculture, PGPR and their interactions with plants have a lot of potentials. Cotton that has been co-inoculated with Azotobacter chroococcum strains has shown to boost plant development and reduce nitrogen fertilizer doses by 50%, according to Romero-Perdomo et al. (2017). Korir et al. also tested the effect of PGPR on common bean nodulation and growth in a lowphosphorous soil under greenhouse conditions. J. Wang et al. also found out that mixed inoculation with Bacillus megaterium and Rhizobium tropici strains raised nodule fresh weight, plant dry weight and root dry weight of plants (Wang et al. 2020). Agriculture must be more productive, environmentally friendly and long-term in the twenty-first century. Fertilizers that provide essential macronutrients such as nitrogen (N), phosphorus (P) and potassium (K) could contribute directly, such as biological N2 fixation, P solubilization and phytohormone production or indirectly, such as antimicrobial compound biosynthesis and elicitation of induced systemic

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resistance, to improve crop yields and fertilizer efficiency. Microbial-based bioformulations that improve plant performance are desperately needed, especially those that have complimentary and synergistic effects with mineral fertilization. Bacteria like nitrogen-fixing (NF) bacteria and P solubilizing/mobilizing bacteria can help increase crop yield and fertilizer efficiency. Plant mineral uptake, crop output and environmental resistance are all improved by the interaction and synergistic effects of those two microbial populations (Bargaz et al. 2018). Bacteria as Effective Microorganisms (EM) can be used as inoculants and can be fermented to produce beneficial organic fertilizers. The Effective Bacteria (EM) is a mixed culture of helpful microorganisms. For instance, fermented organic fertilizers that contain substantial populations of propagating Lactobacillus spp. possess high amounts of intermediate molecules such as organic acids and amino acids that are useful for plant growth (Yamada and Xu 2000). The microbial inoculants are also playing crucial roles in long-term human health maintenance. The latest developments in microbial inoculants and technology, as well as techniques for utilizing this natural, user-friendly biological resource, are also important for long-term plant health management (Alori and Babalola 2018).

References N. Adam, M. Perner, Microbially mediated hydrogen cycling in deep-sea hydrothermal vents. Front. Microbiol. 9(Nov) (2018). https://doi.org/10.3389/fmicb.2018.02873 M.T. Al-mohanna, Bacterial introduction. in Research Gate, April, pp. 679–692 (2017) E.T. Alori, O.O. Babalola, Microbial inoculants for improving crop quality and human health in Africa. Front. Microbiol. 9(Sep) (2018). https://doi.org/10.3389/fmicb.2018.02213 A. Bargaz, K. Lyamlouli, M. Chtouki, Y. Zeroual, D. Dhiba, Soil microbial resources for improving fertilizers efficiency in an integrated plant nutrient management system. Fron. Microbiol. 9 (2018). https://doi.org/10.3389/fmicb.2018.01606 E. Caplice, G.F. Fitzgerald, Food fermentations: role of microorganisms in food production and preservation. Int. J. Food Microbiol. 50(1–2), 131–149 (1999). https://doi.org/10.1016/S01681605(99)00082-3 O.B. Chukwuma, M. Rafatullah, H.A. Tajarudine, N. Ismail, A review on bacterial contribution to lignocellulose breakdown into useful bio-products. Int. J. Environ. Res. Public Health 18(11) (2021). https://doi.org/10.3390/ijerph18116001 C.N.W. Chun, H.A. Tajarudin, N. Ismail, B. Azahari, M.M.Z. Makhtar, L.K. Yan, Bacterial flagellum versus carbon nanotube: a review article on the potential of bacterial flagellum as a sustainable and green substance for the synthesis of nanotubes. Sustainability (switzerland) 13(1), 1–23 (2021). https://doi.org/10.3390/su13010021 P. Elavarasi, M. Yuvaraj, P. Gayathri, Application of bacteria as a prominent source of biofertilizers, in Biostimulants in Plant Science. (IntechOpen, 2020). https://doi.org/10.5772/intechopen.89825 P. García-Fraile, E. Menéndez, R. Rivas, Role of bacterial biofertilizers in agriculture and forestry. AIMS Bioeng. 2(3), 183–205 (2015). https://doi.org/10.3934/bioeng.2015.3.183 T. Gregersen, Rapid method for distinction of gram-negative from gram-positive bacteria. Eur. J. Appl. Microbiol. Biotechnol. 5(2), 123–127 (1978). https://doi.org/10.1007/BF00498806 S.U. Islam, M. Ul-Islam, H. Ahsan, M.B. Ahmed, A. Shehzad, A. Fatima, J.K. Sonn, Y.S. Lee, Potential applications of bacterial cellulose and its composites for cancer treatment. Int. J. Biol. Macromol. 168, 301–309 (2021). https://doi.org/10.1016/j.ijbiomac.2020.12.042

References

33

W. Liu, H. Du, M. Zhang, K. Liu, H. Liu, H. Xie, X. Zhang, C. Si,. Bacterial cellulose based composite scaffolds for biomedical applications: a review (2020) E. Malusá, L. Sas-Paszt, J. Ciesielska, Technologies for beneficial microorganisms inocula used as biofertilizers. Sci. World J. 2012 (2012). https://doi.org/10.1100/2012/491206 M.M. Nakano, P. Zuber, “Strict Aerobe” (Bacillus subtilis). Ann Rev Microbiol 52, 165–1990 (1998) J.M. Rajwade, K.M. Paknikar, J.V. Kumbhar, Applications of bacterial cellulose and its composites in biomedicine. Appl. Microbiol. Biotechnol. 99(6), 2491–2511 (2015). https://doi.org/10.1007/ s00253-015-6426-3 A. Ricci, A. Allende, D. Bolton, M. Chemaly, R. Davies, R. Girones, L. Herman, K. Koutsoumanis, R. Lindqvist, B. Nørrung, L. Robertson, G. Ru, M. Sanaa, M. Simmons, P. Skandamis, E. Snary, N. Speybroeck, B. Ter Kuile, J. Threlfall, H. Wahlström, P.S. Fernández Escámez, Scientific opinion on the update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA. EFSA J. 15(3) (2017). https://doi.org/10.2903/j.efsa.2017.4664 M.H. Richmond, R.B. Sykes, The β-lactamases of gram-negative bacteria and their possible physiological role. Adv. Microb Physiol 9(C), 31–88 (1973). https://doi.org/10.1016/S0065-291 1(08)60376-8 F. Romero-Perdomo, J. Abril, M. Camelo, A. Moreno-Galván, I. Pastrana, D. Rojas-Tapias, R. Bonilla, Azotobacter chroococcum as a potentially useful bacterial biofertilizer for cotton (Gossypium hirsutum): Effect in reducing N fertilization. Rev. Argent. Microbiol. 49(4), 377–383 (2017). https://doi.org/10.1016/j.ram.2017.04.006 R. Rosselli, O. Romoli, N. Vitulo, A. Vezzi, S. Campanaro, F. De Pascale, R. Schiavon, M. Tiarca, F. Poletto, G. Concheri, G. Valle, A. Squartini, Direct 16S rRNA-seq from bacterial communities: a PCR-independent approach to simultaneously assess microbial diversity and functional activity potential of each taxon. Sci. Rep. 6(February), 1–12 (2016). https://doi.org/10.1038/srep32165 W.A. Seleen, C.N. Stark, Some characteristics of green-fluorescent pigment-producing bacteria. J. Bacteriol. 46(6), 491–500 (1943). https://doi.org/10.1128/jb.46.6.491-500.1943 A.M. Sousa, I. Machado, A. Nicolau, M.O. Pereira, Improvements on colony morphology identification towards bacterial profiling. J. Microbiol. Methods 95(3), 327–335 (2013). https://doi.org/ 10.1016/j.mimet.2013.09.020 J. Wang, R. Li, H. Zhang, G. Wei, Z. Li, Beneficial bacteria activate nutrients and promote wheat growth under conditions of reduced fertilizer application. BMC Microbiol. 20(1) (2020). https:// doi.org/10.1186/s12866-020-1708-z C.R. Woese, G.E. Fox, Phylogenetic structure of the prokaryotic domain: the primary kingdoms (archaebacteria/eubacteria/urkaryote/16S ribosomal RNA/molecular phylogeny). Proc. Nat. Acad. Sci. u.s.a. 74(11), 5088–5090 (1977) C.R. Woese, O. Kandler, M.L. Wheelis, Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. Proc. Nat. Acad. Sci. u.s.a. 87(12), 4576–4579 (1990). https://doi.org/10.1073/pnas.87.12.4576 K. Yamada, H.L. Xu, Properties and applications of an organic fertilizer inoculated with effective microorganisms. J. Crop. Prod. 3(1), 255–268 (2000). https://doi.org/10.1300/J144v03n01_21 A.C.S. Yu, J.F.C. Loo, S. Yu, S.K. Kong, T.F. Chan, Monitoring bacterial growth using tunable resistive pulse sensing with a pore-based technique. Appl. Microbiol. Biotechnol. 98(2), 855–862 (2014). https://doi.org/10.1007/s00253-013-5377-9

Chapter 4

Evaluation of Biocoating

4.1 Properties of Films The appropriate characterization of the film properties, which spans from scientific investigation to quality control in industry, is an important element of thin film science and technology. Thin films have characteristics that differ significantly from bulk materials with the same nominal composition. Another issue is the influence of the substrate on these properties, which is particularly significant in characterization where thin film results are typically sought. Thin film materials are critical components of ongoing technical advancements in optoelectronic, photonic and magnetic devices. Many new areas of inquiry in solid state physics and chemistry have sprung up as a result of thin film investigations, which are based on phenomena that are unique to the thickness, geometry and structure of the film. The ability to easily integrate materials into many sorts of devices is made possible by the processing of materials into thin films. Thin films are exceedingly thermally stable and tough, although they are delicate. Organic materials, on the other hand, have good thermal stability and are robust, but they are soft. Tensile testing of freestanding films and the microbeam cantilever deflection technique can be used to determine thin film mechanical properties, however, nanoindentation is the simplest method. Optical experiments are an excellent technique to investigate the characteristics of semiconductors. Thin film materials have been used in semiconductor devices, wireless communications, telecommunications, solar cells, integrated circuits, transistors, light-emitting diodes, photoconductors, rectifiers and light crystal displays, as well as lithography and multifunctional emerging coatings and other emerging cutting technologies. The analysis of films’ properties included in this research included physical and mechanical analysis, chemical analysis and microbial analysis.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_4

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4.1.1 Physical and Mechanical Analysis The physical and mechanical analysis that will be discussed in this part includes tensile strength, breaking strain, toughness, opacity, brightness, conductivity, Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM).

4.1.1.1

Tensile Strength, Breaking Strain and Toughness

The ability of a substance to resist a force that tends to pull it apart is known as tensile strength. It is a measurement of how much force an object can withstand before deforming plastically or undergoing irreversible deformation. An object that has suffered plastic deformation, also known as an unrecoverable strain, can no longer return to its previous shape after the stress has been removed. Keep in mind the difference between toughness and strength: toughness measures the force required to completely collapse a material, whereas strength just measures the force required to produce plastic deformation. Very brittle materials, such as ceramics, literally overlap with strength and toughness in some conditions. There are several types of material strength that are closely related to the different types of stress that an object can experience. Depending on whether the material’s ability to sustain compressive or tensile stress is measured, a material may have different compressive and tensile strength values. Shear strength is a measurement of a material’s capacity to endure shear stress before encountering a sliding failure. Breaking strain is an object that is subjected to stress from any direction is going to distort or completely fail as a result. The strain of an object is a measurement of how much it has deformed in contrast to its original dimensions. By analyzing the link between stress and strain, scientists and engineers have been able to predict how materials will react when subjected to certain forces. This has also made it possible to grade materials based on their material properties, resulting in terms like brittle, ductile, elasticity, hardness, toughness and strength. Toughness refers to a material’s ability to bear a certain level of force without breaking. Keep in mind that the crucial word here is fracture, which refers to a total material failure. This means that a material will undergo elastic deformation or deformation that permits it to return to its original shape, without breaking. Until they fracture, ductile materials are robust. Fracture is a condition that causes a substance to distort. A material’s toughness is thus determined by both its strength and ductility.

4.1.1.2

Opacity and Brightness

Opacity is the ability of a thin, transparent material to hide the surface behind it (Bajpai 2018). It is also known as the contrast ratio or the hiding power. The amount of light that travels through a material is measured by its opacity. The opacity of a

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material determines how much light can travel through it. The higher the opacity, the less light that can pass through it (Gangakhedkar 2010). Opacity can be expressed as black reflectance when the material is backed by a black object or white reflectance when it is backed by a white object. An opacity of 100% means complete hiding: no difference can be seen between the transparent material over black and white. The opacity of the microbial composite films was tested using two different conditions, white light and black light. The difference between these two conditions is that the condition where the films are mounted are either dark or bright. When the films are mounted on the testing machine and covered with a dark hollow cover, the light passing through the films will penetrate into a dark condition and hence, the results are indicated as black light. On the other hand, when the films are mounted on the testing machine and covered with white-coloured cover, the light passing through the films will be blocked by the white-coloured cover and hence, provided results indicated as white light.

4.1.1.3

Conductivity

Conductivity is a measurement of the ability of an aqueous solution to transfer an electrical current. The conductivity increases as the concentration of ions in the solution, their mobility and the temperature of the water rise. Ionic strength is related to conductivity measurements. However, this is not a qualitative experiment, as the presence of specific ions is unknown. The inverse of conductivity is resistance (Derbali et al. 2018).

4.1.1.4

Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry is a thermoanalytical technique that determines the difference in the amount of heat required to raise the temperature of the sample and the reference as a function of temperature. It is a thermoanalytical approach for determining a substance’s thermal characteristics (Sindhu et al. 2015). For DSC analysis, temperature software is often designed to increase the temperature of the sample holder linearly as a function of time. The melting point of the microbial composite films was determined using a beginning temperature of 30 °C and an ending temperature of 400 °C with an increasing temperature of 10 °C/min in this study.

4.1.1.5

Thermogravimetric Analysis (TGA)

Thermogravimetric analysis (TGA) is an analytical technique that monitors the weight change that occurs as a sample is heated at a constant pace to evaluate the thermal stability of a material and its fraction of volatile components (Rajisha et al.

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2011). TGA is commonly used to determine a material’s decomposition temperature. The TGA graph might be evaluated in such a way that when the temperature rises, the materials’ components will decompose according to their decomposition temperature and the residues will be seen in the data. The microbial composite films were heated at a rate of 10 °C/min in this experiment.

4.1.1.6

Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX)

A scanning electron microscope is a type of electron microscope that, by scanning the surface with a focused electron beam, produces images of a sample (Raghavendra and Pullaiah 2018). Electrons interact with atoms in the sample, resulting in a variety of signals that give information about the topography and composition of the sample. EDX is a chemical microanalysis technology that is used in conjunction with SEM. In EDX spectroscopy, the number and energy of X-rays emitted from a material after excitation with an electron beam are quantified, allowing elemental identification (Moros et al. 2018). The cross-sectional and surface of sodium alginate film, as well as log phase, stationary phase and lag phase microbial composite films, were studied under SEM in order to produce high-resolution 3D images on the surface of two participants in this study. At the same time, EDX was used to determine the components present in the films.

4.1.2 Chemical Analysis 4.1.2.1

Fourier-Transform Infrared Spectroscopy (FTIR)

Fourier-transform infrared spectroscopy is a technique for obtaining an infrared spectrum of absorption or emission of a solid, liquid or gas. It detects chemical bonds in a molecule by forming an infrared absorption spectrum. The spectrum produces a sample profile, which is a unique molecular fingerprint that may be used to screen and scan samples for a variety of components (Faghihzadeh et al. 2016). An FTIR spectrometer collects high-spectral-resolution data over a large spectral range at the same time. The materials for this study endeavour were films, hence Attenuated Total Reflectance-Fourier-transform infrared (ATR-FTIR) was used. ATR stands for accessory units that can be utilized in conjunction with FTIR spectrometers. This is a sampling technique that, when combined with infrared spectroscopy, allows samples to be analyzed in their natural condition, whether solid or liquid (Macotpet et al. 2020).

4.2 Mechanism to Improve Conductivity by Integration of Bacteria …

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4.1.3 Microbial Analysis 4.1.3.1

Microbial Viability

Microbial viability is defined in microbiology as the repetitive division of a cell on an agar surface to generate a visible colony, which is subsequently accepted as irrefutable proof of vitality (Davey 2011). One of the most common tests performed in microbiology laboratories around the world is determining microbial viability in samples. In general, this method entails growing colonies on a nutrient agar surface for an incubation time (Postgate 1969). Microbial viability is important in this research as it determines whether Bacillus subtilis could survive through the experiment.

4.2 Mechanism to Improve Conductivity by Integration of Bacteria and Metal Ions Metal ions provide access to physical properties such as magnetic properties, conductivity and catalytic activity. Metal ions are also crucial in regulating the structures and functions of several biological molecules. They can influence biological processes directly or indirectly (Shukla and Leszczynski 2014). Heavy metals (HMs) can be found in both essential and non-essential forms in the environment. HM ions are introduced into the soil biota through a range of natural and anthropogenic sources. Essential HMs or micronutrients include cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), aluminium (Al), nickel (Ni) and zinc to help plants grow and develop (Zn). Copper is a critical micronutrient since it is required by several enzyme systems and stimulates various enzymes involved in plant lignin synthesis. It is also necessary for photosynthesis, essential for plant respiration and aids in plant glucose and protein metabolism. These beneficial micronutrients improve the nutritional status of the plant as well as a number of mechanisms that are required for healthy plant growth and productivity. Nevertheless, these micronutrients have a wide range of optimality for land plants. Heavy metals are absorbed by plants as a soluble component or are solubilized by root exudates. When they are present in excess, they become toxic to plants, affecting their ability to absorb and accumulate non-essential components. The increasing concentration of HMs in plant tissue has both direct and indirect harmful effects. Direct consequences include the creation of oxidative stress, which exacerbates cytoplasmic enzyme inhibition and cell structural destruction. Despite that, if the level of metal ions or micronutrients are controlled at the suitable level for plants, these ions could function accordingly and are very beneficial for plant growth and development. Additionally, they have the ability to alter the function of many enzymes and proteins, halt metabolism and disclose phytotoxicity (Arif et al. 2016).

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There are many different types of bacteria with different functions and characteristics present on earth. Some bacteria are also known to have the ability to conduct electricity. Extracellular electron transfer or EET, is a method through which bacteria produce electricity by generating electrons within their cells and then transporting those electrons beyond their cell membranes via microscopic channels formed by surface proteins. These bacteria are called electrogenic bacteria and Bacillus subtilis is one of the excellent electrogenic bacteria. The conductivity of bacteria can be related to its ability in taking up metal ions from its surroundings. The conductivity is also affected by suspended matter and also depends upon the amount of ions present (Saleh et al. 2021). Some of the common sources of these metal ions are from heavy metals discharged from the industries or those that are already available in the environment. Due to the ability of bacteria to remediate these inorganic metals, there is an increasing demand in bacteria-based heavy metal bioremediation as a viable alternative to conventional approaches that involve chemicals. To be able to do this, there are a few types of mechanisms that are involved in this process such as biosorption, intracellular sequestration and extracellular sequestration (Igiri et al. 2018). The biosorption potential of bacteria has shown synergetic benefits with a manyfold increase in the removal of heavy metals (Igiri et al. 2018). It has proven to be very promising, offering significant advantages such as availability, low-cost, profitability, ease of operation and great efficiency, especially when dealing with low concentrations. Industrial microorganisms such as bacteria, algae, fungus and yeast can efficiently accumulate heavy metals as biosorbent. Transport across the cell membrane, ion exchange, complexation, precipitation and physical adsorption were all key biosorption mechanisms. To completely appreciate how metals bind to biomass, it is necessary to identify the functional groups involved in metal binding. The majority of these species’ cell walls must be identified. The functional sites in the biosorbent that are responsible for metal adsorption include carboxyl, imidazole, sulfydryl, amino, phosphate, sulphate, thioether, phenol, carbonyl, amide and hydroxyl moieties. By changing surface reactive sites, surface grafting and functional group exchange could be employed to improve biosorbents (Publishing and Science 2014). Intracellular sequestration is another way that could be involved. Intracellular sequestration is caused by metal ions that are complexed by a variety of molecules in the cell cytoplasm. Metals’ interactions with surface ligands, followed by sluggish transport into the cell, can lead to high metal concentrations within microbial cells. Peptidoglycan, polysaccharide and lipid components of the cell wall are rich in metal-binding ligands such as −OH, −COOH, −RCOO, −NH2 and −SH. These functional groups are extremely helpful in the intracellular sequestration process. Because it binds to anionic metal species via electrostatic interaction and cationic metal species via surface complexation, amine is more active in metal absorption than the other functional groups (Igiri et al. 2018). A cadmium-tolerant Pseudomonas putida strain, for example, was able to sequester copper, cadmium and zinc ions intracellularly using cysteine-rich low molecular weight proteins. Bacterial ability

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to accumulate metals intracellularly has been employed in a variety of applications, the most notable of which being wastewater treatment (Higham et al. 1986). Extracellular sequestration occurs when metal ions are deposited in the periplasm by cellular components or when metal ions are complexed as insoluble compounds. Bacteria can discharge metal ions from the cytoplasm and sequester them in the periplasm. Metal precipitation is the extracellular sequestration of metals. Ironreducing bacteria, such as Geobacter spp. and sulphur-reducing bacteria, such as Desulfuromonas spp., can reduce dangerous metals to fewer or benign metals. Zinc ions can pass from the cytoplasm into the periplasm of Synechocystis PCC 6803 strain via the efflux mechanism (Thelwell et al. 1998). Copper-inducible proteins CopA, CopB (periplasmic proteins) and CopC (outer membrane protein) are produced by copper-resistant Pseudomonas syringae strains and bind copper ions and microbial colonies.

4.2.1 Biosorption of Metal Ions Biosorption refers to the ability of a biological mass to absorb ions from waterrelated substances through a variety of metabolically or physicochemical processes. The passive adsorption of harmful chemicals by dead, inactive or biologically generated materials is also known as biosorption. Absorption, adsorption, ion exchange, surface complexing and precipitation processes are all used in biosorption. It is a self-sustaining mechanism that is unaffected by microbial metabolism. Biosorption is a key process in environmental protection as well. Biosorption is the result of many metabolic processes that occur inside or outside of the cell membrane; the mechanisms responsible for pollutant absorption differ depending on the type of biomass used. Bacteria, fungi, algae and some industrial and agricultural wastes are among the biomaterials that can perform biosorption. Bacterial biosorption can be used in many applications such as to remove contaminants from waters contaminated with non-biodegradable pollutants like metals and dyes by absorbing or adsorbing them. The sorption capacities of bacterial biomass toward metal ions are dependent on the conditions involved. The features of cell wall elements like peptidoglycan, as well as the involvement of functional groups like amine, carboxyl and phosphonate, influence the biosorption potentials of bacteria (Ansari et al. 2011). Microorganisms such as bacterial cell walls are mostly polysaccharides, proteins and lipids, with carboxyl, sulphate, phosphate and amino groups to create interactions with metals and their complexes (Fomina and Michael 2014). This type of biosorption happens quickly and can be reversed (Mustapha and Halimoon 2015).

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4.3 Mechanism to Retain Moisture Content Using Glycerol Glycerol (CAS Registry Number 56–81-5) is a colourless, odourless, sweet-tasting liquid that is the simplest trihydric alcohol. It is a naturally occurring chemical with a wide range of industrial, consumer, food and medical applications. Glycerol occurs naturally and is found in all animal and vegetable fats and oils in the form of esters (glycerides). Glycerol is normally used as a sweetener, a humectant, a solvent and a feeding stock for microbial cultures in the food, chemical, pharmaceutical and biotechnology sectors (Frigaard 2018). Glycerol is also utilized as a plasticizer to improve the mobility of polymer chains in films by reducing intermolecular tensions and lowering the glass transition temperature of the material. As a plasticizer, glycerol improves the ability of biopolymers to absorb water and acts as a crystal-forming agent (Inayati et al. 2019). This property aids the ability of films containing glycerol to achieve better conductivity as well. Furthermore, glycerol aids in the growth and development of plants. It aids in the germination and roots of seeds and plants. Indolebeta-acetic acid, found in glycerol, aids in the growth of healthier and stronger roots, leading in enhanced productivity. Glycerol, on the other hand, has been demonstrated to have a high potential value as a soil conditioner and to aid in the increase of soil organic carbon content. However, glycerol requires additional fertilizer in this scenario to allow for nitrogen tie-up by microbes during soil decomposition (Vassilev et al. 2017). More importantly, glycerol is considered non-toxic and environmentally friendly. According to Safety Data Sheet, National Diagnostics, it is not considered a hazardous substance or mixture according to regulation (EC) No. 1272/2008. This is because glycerol is mainly distributed to water when discharged into the environment, with minor amounts distributed to air, soil or sediment and it is not predicted to bioaccumulate (Wernke 2014). The mechanisms involved in retaining moisture of a suitable substance with glycerol included the inspection of the surface physicochemical properties. Moisture adsorption behaviour of a substance loaded with glycerol during the transfer of water molecules is due to intra- and intermolecular hydrogen bonding, where glycerol extended the amorphous region and hence increased the active adsorption sites with improvement on moisture transport resistance (Stevanic and Salmén 2020). The intermolecular hydrogen bonds can be attributed to the H–O–H stretching of absorbed water due to the presence of glycerol (Xin et al. 2015). The increased active adsorption sites also improve the moisture adsorption capacity. Research has shown that loading glycerol changes the water content in the substances. In glycerol-treated substances, immobile water predominates during adsorption and bound water increases when the immobile water is saturated. These findings serve as benchmarks for improving moisture-retaining capabilities of various substances during the production process. The number of hydrophilic functional groups in the amorphous area and the scattered water adsorption sites also influence the moisture adsorption ability significantly. The pore characteristics and permeability are linked to moisture diffusion resistance during the adsorption process. The primary component of a substance to be examined is the crystalline structure with intramolecular and intermolecular

4.5 Soil Nutrients Analysis

43

hydrogen bonding. The hydrogen bond connects water molecules on the substance to their amorphous area. The hydroxyl group of glycerol also aided in the establishment of a hydrogen bond between the water molecule and the substance. During water vapour adsorption, both the hydroxyl group and the moisture content were positively associated with the glycerol level. Because of its extreme hygroscopicity, the presence of glycerol automatically accounts for the increased water adsorption sites and hence, increases the ability of retaining moisture (Xin et al. 2015).

4.4 Plant Growth Analysis Plant growth analysis is a method for evaluating plant shape and function that is explanatory, holistic and integrative. It investigates processes inside and involves the entire plan using simple primary data such as weights, areas and contents of plant components (Hunt et al. 2002). A change in biomass amount accompanied by an irreversible increase in plant size is termed as growth (weight). A qualitative change in plant shape or function, such as the transition from vegetative to reproductive growth, is referred to as ‘development.’ Cell division and expansion are both involved in growth, which refers to the permanent changes in the size of a cell organ or complete plant. Plant growth can be quantified in terms of length or plant height, leaf area, leaf weight, fresh and dried weight and other variables. Plant growth analysis is needed to explain differences in plant development growing in the same environment or different habitats (Pandey et al. 2017). Growth and development cycles in natural habitats must be completed within a time frame specified by environmental factors, such as light, moisture and nutrition, which often limit the expression of genetic potential. The notion of relative growth rate (RGR) and the simple RGR equation, which stems from the growth of cell populations with unconstrained resources that is, where light, space and nutrition supply are not limited, are the most relevant and often used analyses. Cell number is an impractical metric of growth in whole plants. Instead, fresh or oven-dried biomass (W) is used as a substitute for cell development and the number of days between measurements is used as a reference. The relative growth rate (RGR) is currently used instead of r and it is measured in days or weeks rather than hours.

4.5 Soil Nutrients Analysis Soil nutrient analysis, commonly known as soil testing, is a low-cost and rapid way of assessing the availability of nutrients in soils. Soil analysis is a set of chemical procedures for determining not only the amount of plant nutrients in the soil, but also the chemical, physical and biological aspects of the soil that are necessary for plant nutrition or ‘soil health.’ (Page et al. 2020). Soil analysis is frequently performed to detect whether the supply of nutrients supply is limiting plant growth (Prasad

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and Djanaguiraman 2016). It largely reflects the soil’s ability to provide nutrients to plants, however, it does not accurately reflect nutrient mobility in the soil. It also leaves out information on soil structure, microbial activity and plant factors including root growth and root-induced rhizosphere alterations, all of which are crucial for nutrient uptake in the field (Marschner and Rengel 2011). The amount of key plant nutrients such as nitrogen, phosphorus, potassium, trace elements and other physical qualities are determined through chemical soil analysis. Soil analysis entails collecting soil samples, analyzing the results in the lab and interpreting the findings with fertilizer recommendations. It is easier to determine the amount of fertilizers required to obtain high and quality harvests based on the quantity of nutrients in the soil as determined by chemical analysis and the culture’s requirements for a certain yield. Plants may absorb up to 80% of nitrogen, 40% of phosphorus and 60% of potassium in ideal soil conditions, which should be considered when determining the amount of nutrients. High-quality soil analysis provides the foundation for fertilization planning and thus the overall quality of the production cycle, resulting in higher quality and yield, as well as better farm management.

4.6 Mathematical Modelling The process of portraying a real-world situation in a mathematical form, such as graphs, equations, diagrams, scatterplots, tree diagrams and so on, is known as mathematical modelling. Modelling is the process of turning real-life events into language or transforming problems from mathematical explanations to a compelling setting. According to this viewpoint, mathematical models are an essential part of all branches of mathematics, including arithmetic, algebra, geometry and calculus. When new mathematical modelling research modelling is examined, it becomes evident how important modelling is (Dundar et al. 2012). Some of the common mathematical modelling techniques are nonlinear models and linear models. Simple linear models (y = mx + b) connect two variables (X and Y ) with a straight line, where ‘b’ is the point, where the line intersects the ‘y axis’ and ‘m’ denotes the slope of the line. The slope or gradient of a line describes how steep a line is. Nonlinear models connect the two variables in a curved manner. Formulation, solution, interpretation and validation are the processes involved in mathematical modelling. Mathematical modelling can be utilized for a variety of purposes. The state of knowledge about a system, as well as how well the modelling is done, determines how successfully any given purpose is achieved. Developing scientific understanding through quantitative expression of existing knowledge of a system is an example of the spectrum of objectives. Second, evaluate the impact of system changes. Third, assist decision-making, including tactical and strategic judgements by managers and planners. In this study, mathematical modelling is implied to simulate the plant growth analysis as well as soil nutrient analysis. It involves the growth and development of plants and its interactions with its environment and most importantly, the conditions of fertilizers applied to plants.

References

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References M.I. Ansari, F. Masood, A. Malik, Bacterial biosorption: a technique for remediation of heavy metals, in: Microbes and Microbial Technology: Agricultural and Environmental Applications (Springer, New York, 2011), pp. 283–319. https://doi.org/10.1007/978-1-4419-7931-5_12 N. Arif, V. Yadav, S. Singh, S. Singh, S. Ahmad, R.K. Mishra, S. Sharma, D.K. Tripathi, N.K. Dubey, D.K. Chauhan, Influence of high and low levels of plant-beneficial heavy metal ions on plant growth and development, in Frontiers in Environmental Science, vol 4, no NOV. (Frontiers Media S.A., 2016) https://doi.org/10.3389/fenvs.2016.00069 P. Bajpai. Paper and its properties Biermann’s handbook of pulp and paper (2018), pp. 35–63 https:// doi.org/10.1016/b978-0-12-814238-7.00002-7 H.M. Davey, Life, death, and in-between: Meanings and methods in microbiology. Appl. Environ. Microbiol. 77(16), 5571–5576 (2011). https://doi.org/10.1128/AEM.00744-11 L. Derbali, M. Dkhili, S. Zargouni, M. Ouadhour, R. Riahi, H. Ezzaouia, Superlattices and microstructures laser ablation microgrooving and nanostructured silicon surfaces for an effective gettering process and reduced optical losses ( a ) ( b ). Superlattices Microstruct. 123(June), 427–435 (2018). https://doi.org/10.1016/j.spmi.2018.09.031 S. Dundar, B. Gokkurt, Y. Soylu, Mathematical modelling at a glance: a theoretical study. Procedia. Soc. Behav. Sci. 46, 3465–3470 (2012). https://doi.org/10.1016/j.sbspro.2012.06.086 F. Faghihzadeh, N.M. Anaya, L.A. Schifman, Fourier transform infrared spectroscopy to assess molecular-level changes in microorganisms exposed to nanoparticles. Nanotechnol. Environ. Eng. 1(1), 1–16 (2016). https://doi.org/10.1007/s41204-016-0001-8 M. Fomina, G. Michael, Bioresource technology biosorption: current perspectives on concept, definition and application. Biores. Technol. 160, 3–14 (2014). https://doi.org/10.1016/j.biortech. 2013.12.102 N.U. Frigaard, Sugar and sugar alcohol production in genetically modified cyanobacteria, in Genetically Engineered Foods, vol 6 (Elsevier Inc., 2018), pp. 31–47 https://doi.org/10.1016/B978-012-811519-0.00002-9 N.S. Gangakhedkar, Colour measurement of paint films and coatings. Colour Measur.: Principles, Adv. Ind. Appl. 279–311 (2010). https://doi.org/10.1533/9780857090195.2.279 D.R. Higham, P.J. Sadler, M.D. Scawent, Cadmium-binding proteins in pseudomonas putida: pseudothioneins, in Environmental Health Perspectives, vol 65 (1986) R. Hunt, D.R. Causton, B. Shipley, A.P. Askew, A modern tool for classical plant growth analysis. Ann. Bot. 90(4), 485–488 (2002). https://doi.org/10.1093/aob/mcf214 B.E. Igiri, S.I.R. Okoduwa, G.O. Idoko, E.P. Akabuogu, A.O. Adeyi, I.K. Ejiogu, Toxicity and bioremediation of heavy metals contaminated ecosystem from tannery wastewater: a review. J. Toxicol (2018). https://doi.org/10.1155/2018/2568038 P.D.J Inayati, M.P.N. Matovanni, Effect of glycerol concentration on mechanical characteristics of biodegradable plastic from rice straw cellulose, in AIP Conference Proceeding, vol 2097 (2019). https://doi.org/10.1063/1.5098285 A. Macotpet, E. Pattarapanwichien, S. Chio-srichan, Attenuated Total Reflection Fourier Trans. Infrared Primary Screen. Meth. Cancer Canine Serum 21(1), 1–10 (2020) P. Marschner, Z. Rengel, Nutrient availability in soils, in Marschner’s Mineral Nutrition of Higher Plants: Third Edition (Elsevier Ltd., 2011). https://doi.org/10.1016/B978-0-12-384905-2.000 12-1 M. Moros, L. Gonzalez-Moragas, A. Tino, A. Laromaine, C. Tortiglione, Invertebrate models for hyperthermia: what we learned from caenorhabditis elegans and hydra vulgaris, in Nanomaterials for Magnetic and Optical Hyperthermia Applications (Elsevier Inc., 2018). https://doi.org/10. 1016/B978-0-12-813928-8.00009-0 M.U. Mustapha, N. Halimoon, Microorganisms and biosorption of heavy metals in the environment: a review paper. J. Micro. Biochem. Technol. 07(05), (2015). https://doi.org/10.4172/1948-5948. 1000219

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4 Evaluation of Biocoating

K.L. Page, Y.P. Dang, R.C. Dalal, The ability of conservation agriculture to conserve soil organic carbon and the subsequent impact on soil physical, chemical, and biological properties and yield. Front. Sustain. Food Syst. 4(March), 1–17 (2020). https://doi.org/10.3389/fsufs.2020.00031 R. Pandey, V. Paul, M. Das, M. Meena, R.C. Meena, Plant Growth Analysis Paper. November (2017). https://doi.org/10.13140/RG.2.2.21657.72808 J.R. Postgate, Chapter XVIII viable counts and viability. Meth. Microbiol. 1(3), 611–628 (1969). https://doi.org/10.1016/S0580-9517(08)70149-1 P.V.V. Prasad, M. Djanaguiraman, Iron chlorosis, in Encyclopedia of Applied Plant Sciences, 2nd Edn, vol 1. (Elsevier, 2016). https://doi.org/10.1016/B978-0-12-394807-6.00122-2 I.W.A. Publishing, W. Science, Mechanisms of heavy metal removal using microorganisms as biosorbent Vahid Javanbakht Seyed Amir Alavi and Hamid Zilouei (2014), pp. 1775–1787 https:// doi.org/10.2166/wst.2013.718 P. Raghavendra, T. Pullaiah, Biomedical imaging role in cellular and molecular diagnostics. Adv. Cell Mol. Diag. 85–111 (2018). https://doi.org/10.1016/b978-0-12-813679-9.00004-x K.R. Rajisha, B. Deepa, L.A. Pothan, S. Thomas, Thermomechanical and spectroscopic characterization of natural fibre composites, in Interface Engineering of Natural Fibre Composites for Maximum Performance (2011), pp. 241–274. https://doi.org/10.1533/9780857092281.2.241 L.I.F. Saleh, R.O. Rashed, S.M. Muhammed, Evaluation of heavy metal content in water and removal of metals using native isolated bacterial strains. Biodiversitas 22(8), 3163–3174 (2021). https:// doi.org/10.13057/biodiv/d220810 M.K. Shukla, J. Leszczynski, Nucleic acids: ground-state and excited-state properties, structures, and interactions and environmental aspects as revealed by computational studies, in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering (Elsevier, 2014). https:// doi.org/10.1016/b978-0-12-409547-2.11020-0 R. Sindhu, P. Binod, A. Pandey, Microbial poly-3-hydroxybutyrate and related copolymers, in Industrial Biorefineries and White Biotechnology (Elsevier B.V., 2015) https://doi.org/10.1016/ B978-0-444-63453-5.00019-7 S.J. Stevanic, L. Salmén, Molecular origin of mechano-sorptive creep in cellulosic fibres. Carbohyd. Polym. 230 (2020). https://doi.org/10.1016/j.carbpol.2019.115615 C. Thelwell, N.J. Robinson, J.S. Turner-Cavet, An SmtB-Like Repressor from Synechocystis PCC 6803 Regulates a Zinc Exporter, vol 95, no 18 (1998) N. Vassilev, E. Malusa, A.R. Requena, V. Martos, A. López, I. Maksimovic, M. Vassileva, Potential application of glycerol in the production of plant beneficial microorganisms. J. Ind. Microbiol. Biotechnol. 44(4–5), 735–743 (2017). https://doi.org/10.1007/s10295-016-1810-2 M.J. Wernke, Glycerol, in Encyclopedia of Toxicology: Third Edition (Elsevier, 2014), pp. 754–756. https://doi.org/10.1016/B978-0-12-386454-3.00510-8 S. Xin, H. Yang, Y. Chen, M. Yang, L. Chen, X. Wang, H. Chen, Chemical structure evolution of char during the pyrolysis of cellulose. J. Anal. Appl. Pyrol. 116, 263–271 (2015). https://doi.org/ 10.1016/j.jaap.2015.09.002

Chapter 5

Biocoating Evaluation Techniques

5.1 Growth Profile of Bacillus subtilis Bacillus subtilis is initially thawed using gentle agitation in a water bath that is set to 30 °C. The bacterial cells are thawed for approximately 2 min until all ice melts. 100 µl of Bacillus subtilis stock culture is then transferred into a nutrient agar petri dish using a micropipettor. Spread plate is performed to spread the bacteria cells evenly across the agar on petri dish. The petri dish is then incubated at 37 °C to revive the bacterial cells. Examination of bacterial cells is done 24 h post incubation. Subculturing of Bacillus subtilis is carried out in order to obtain healthy bacterial cells before cultivation in universal bottles as stock liquid culture for large-scale cultivation in a conical flask. Cultivation of Bacillus subtilis is carried out using liquid broth culture method according to the BENSON Manual for Microbiological Applications (Afreen et al. 2020). In this study, Penassay broth was used as it provides sufficient amount of nutrients for the optimum growth of Bacillus subtilis. The ingredients of Penassay broth are 10 g peptone, 1.5 g yeast extract, 1.5 g beef extract. 3.5 g sodium chloride, 1.0 g glucose, 3.68 g dibasic potassium phosphate and 1.32 g monobasic potassium phosphate. The broth media were autoclaved before the cultivation of bacterial cells to destroy all possible microorganisms that could contaminate the broth media during cultivation of bacteria (Trevors 1996). One loop of single colony Bacillus subtilis cells was transferred (from the agar) into a universal bottle containing 10 mL of broth media using an inoculating loop. All these processes were performed in a laminar flow hood. The universal bottle is then incubated in the shaker for 24 h at 37 °C. The last stage of the bacterial cell cultivation is done by transferring the culture from the universal bottle into a 1000 mL conical flask with autoclaved Penassay broth. The conical flask is then incubated in the shaker for 24 h at 37 °C. Absorbance reading at 600 nm is taken at an interval of one hour during the 24-h incubation process. Simultaneously, 10 mL of culture is sampled at every hour interval for bacterial biomass study. The data obtained is used to construct the growth profile of Bacillus subtilis. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_5

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5.2 Growth Kinetics of Bacillus subtilis Growth kinetics of Bacillis subtilis is determined by using the info obtained from the growth profile of Bacillis subtilis. The parameters of growth kinetics in this study include doubling time (Td), biomass, maximum biomass, biomass productivity, growth rate, maximum growth rate, specific growth rate, specific maximum growth rate, substrate consumption and yield coefficient for biomass formation. The absorbance at 600 nm of Bacillus subtilis culture is taken at one-hour intervals for 28 h. As mentioned earlier, the culture broth used in this research is Penassay broth where glucose is one of the ingredients. Glucose is taken as a substrate in this research project during the cultivation of Bacillus subtilis. Thereafter, the dinitrosalicylic acid (DNS) method is carried out to determine the amount of reducing sugars present in the culture broth throughout the cultivation process. The DNS method is chosen because it gives a rapid and simple estimation of the extent of saccharification by measuring the total amount of reducing sugars present in the hydrolysate, which was acquired from the bacterial culture obtained from the cultivation of Bacillus subtilis. The substrate concentration of the culture broth throughout the 28 h of cultivation is determined from the concentration of glucose obtained from the DNS method. In this research, in order to determine the substrate consumption by Bacillus subtilis during the cultivation process, the glucose content present in the Penassay broth is taken as a substrate that aided the growth of Bacillus subtilis. Therefore, the substrate concentration of the culture broth is determined from the DNS method as described above.

5.3 Culturing of Bacillus subtilis (Lag Phase, Log Phase, Stationary Phase) Bacillus subtilis was cultured for three different phases which are lag phase. log phase or exponential phase and finally, stationary phase. The three phases of the bacterial culture as mentioned are determined using the growth profile constructed. Referring to Fig. 5.1, the lag phase of Bacillus subtilis growth curve is from the beginning of the cultivation until the 6th hour of the growth profile. Therefore, in order to obtain the culture of Bacillus subtilis at lag phase, the culture is incubated in the shaker for 6 h and then harvested. For the log phase or exponential phase of Bacillus subtilis, the culture is incubated in the shaker until the 22nd hour while for the stationary phase of Bacillus subtilis, the culture is incubated in the shaker until 25th hour.

5.4 Harvesting of Bacillus subtilis

49

0.5

Biomass Production (g/L)

0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0

5

10

15

20

25

30

Time (h)

Fig. 5.1 Graph of biomass production (g/L) versus time (h) of Bacillus subtilis

5.4 Harvesting of Bacillus subtilis The harvesting of Bacillus subtilis culture is done by centrifuging the culture at 5000 rpm for 10 min at 4 °C to separate the bacteria from the liquid broth. The pellet of bacteria is collected and stored at −20 °C before proceeding to the next step of the experiment, which is the freeze-drying of bacterial cells. Figure 5.2 shows the pellet of Bacillus subtilis after centrifugation.

Fig. 5.2 Pellet of Bacillus subtilis after centrifugation

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Fig. 5.3 Powder form of Bacillus subtilis

5.5 Freeze-Drying of Bacillus subtilis The freeze-drying of the microbial composite films is performed using Labconco FreeZone freeze dryer (Labconco, U.S.A.). The collected bacterial sample is freezedried for 24 h at –41 °C by using a freeze dryer to remove all the moisture content. The freeze-dried Bacillus subtilis sample is converted to a fine powder form using a mortar and pestle. Figure 5.3 shows the powder form of Bacillus subtilis while Fig. 5.4 shows the Labconco FreeZone freeze dryer (Labconco, U.S.A).

5.6 Preparation of Microbial Composite Films The film-forming solution is prepared by slowly adding 2 g of sodium alginate powder to a 150 mL of distilled water (Rhim 2004). The solutions were autoclaved beforehand to ensure all the possible microbes present to be destroyed. They are then boiled at 100 °C on a hot plate with continuous stirring by using a magnetic stirrer until the sodium alginate powder dissolved completely. When the temperature reaches 40 °C, different amounts of Bacillus subtilis of 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g and 0.6 g are added to six different solutions, respectively. A solution contained only sodium alginate without biomass of Bacillus subtilis is prepared as a control or constant variable.

5.7 Properties/Testing of Microbial Composite Films

51

Freeze Dryer Follow SOP

Fig. 5.4 Labconco FreeZone freeze dryer (Labconco, U.S.A)

Glass moulds with dimensions of 16 cm (length) × 16 cm (width) × 1.5 cm (height) are used for the casting of microbial composite films (Refer to Fig. 5.5). The film-forming solution containing a respective amount of Bacillus subtilis is then poured into different glass moulds. The bubbles formed during pouring process are removed by using a dropper. The films are then transferred to dry in a drying oven at 40 °C for 24 h. The dried films were peeled off from the glass moulds gently after the drying process (Rhim 2004) (Refer to Fig. 5.6). Crosslinking of dried microbial composite films is performed by using calcium chloride (CaCl2 ) solution through immersion method. In order to obtain a 2% (w/v) CaCl2 solution, 8 g of CaCl2 is measured by using an electronic balance before mixed with 400 mL of distilled water. The dried films are then immersed in 2% (w/v) CaCl2 solution for 2 min for the crosslinking process to occur (Rhim 2004). The treated films were then placed between blotting papers to prevent curling of films during the drying process at ambient conditions.

5.7 Properties/Testing of Microbial Composite Films 5.7.1 Physical and Mechanical Properties of Microbial Composite Films The physical and mechanical properties that are discussed in this part include thickness, tensile strength, breaking strain, toughness, opacity, brightness, conductivity,

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Fig. 5.5 Glass mould of 16 cm (length) × 16 cm (width) × 1.5 cm (height)

Fig. 5.6 Microbial composite film

water absorption, Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM).

5.7 Properties/Testing of Microbial Composite Films

53

Fig. 5.7 Precision micrometre model No. 49-61 (Testing Machines Inc., U.S.A.)

5.7.1.1

Thickness

The thickness of the microbial composite films is determined based on TAPPI T411 standard (Abdul Khalil et al. 2017). The thickness of the film is measured by using a Precision Micrometre Model No. 49-61 (Testing Machines Inc., U.S.A.). The precision micrometre is calibrated before any measurement in order to prevent the error of the measurement. The thickness of each film is measured based on five randomly chosen spots. The average results are calculated and tabulated. Figure 5.7 shows the Precision Micrometre Model No. 49-61 (Testing Machines Inc., U.S.A.).

5.7.1.2

Tensile Strength, Breaking Strain and Toughness

The tensile strength analysis is carried out by using a Texture Analyzer based on ASTM D882 standard test method using TA.XT Plus Texture Analyzer (Stable Micro Systems, U.K.). The microbial composite films are cut into a uniform rectangular shape with dimensions of 8 cm (length) × 1.5 cm (width). To measure the tensile strength of the microbial composite films, the cross-sectional area of each film is first entered into the analysis software machine. The film is then placed in the clamping jaws and the tensile test is carried out. The speed of testing is maintained at 10 mm/s throughout the tensile test. The tensile force is exerted by the machine on the film until the film breaks. The percentage breaking strain (%) and toughness (MJ/m3 ) of the film is measured at the same time. The results obtained are upto three significant figures. Figure 5.8 shows the TA.XT Plus Texture Analyzer (Stable Micro Systems, U.K.).

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Fig. 5.8 TA.XT plus texture analyzer (Stable Micro Systems, U.K.)

5.7.1.3

Opacity

The opacity of the microbial composite films is determined based on ASTM D1746 - 97 which is the standard test method for transparency of plastic sheeting using Brightimeter Micro S5 (Technidyne Corporation, U.S.A). The opacity is assessed using two alternative methods: white light and black light. The films are mounted atop a light source that allows light to pass through them and the light source is hidden under a cover. The film is covered with a white solid for white light opacity, creating a white background for the film. The film is covered with a hollow dark tube to produce a dark background for the film for black light opacity.

5.7.1.4

Brightness

The brightness of the microbial composite films is determined based on ASTM D985 which is the standard test method for brightness of pulp, paper and paperboard using Brightimeter Micro S5 (Technidyne Corporation, U.S.A). The films are mounted on a light source where light can penetrate through the films and the light spot is covered using a heavy knob that ensures no disturbance from external light source during the analysis. Each film is tested on three different spots in order to get the average. Figure 5.9 shows the Brightimeter Micro S5 (Technidyne Corporation, U.S.A).

5.7.1.5

Conductivity

The conductivity of the microbial composite films is determined based on ASTM F1711 four-point-probe method which is the standard test method for measuring

5.7 Properties/Testing of Microbial Composite Films

55

Fig. 5.9 Brightimeter micro S5 (Technidyne Corporation, U.S.A)

sheet resistance of thin film conductors for flat panel display manufacturing using a Digital Multimeter UT33D (Uni-Trend Technology, China). The digital multimeter is turned on to voltage detection of 2000 mV which means it detects up to 2000 mV of voltage. Two probes from the digital multimeter are connected to the microbial composite film through a crocodile clipper. The film is then connected to a 1.5 V battery that acts as a source of current via the two other probes. The conductivity of the films is evaluated from a digital multimeter by the voltage recorded. Figure 5.10 shows the Digital Multimeter UT33D (Uni-Trend Technology, China).

5.7.1.6

Water Absorption

Water absorption of the microbial composite films is determined according to the Water Absorption ASTM D570 standard test method. The microbial composite films are cut into smaller films with dimensions of 30 mm × 30 mm and are put into a drying oven for 24 h at 105 °C. The dry weight of each film is measured before it is soaked in distilled water for 24 h. After the water absorption process is completed, the films are taken out and the wet weight of each film is measured. Figure 5.11 shows the microbial composite films before water absorption while Fig. 5.12 shows the microbial composite films after water absorption. The water absorption properties of the films are calculated by using the following formula:

Water Absorption(%) =

Wet Weight(g) − Dry Weight(g) × 100% Dry Weight(g)

(5.1)

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Fig. 5.10 Digital multimeter UT33D (Uni-Trend Technology, China)

Fig. 5.11 Microbial composite films before water absorption process

5.7.1.7

Differential Scanning Calorimetry (DSC)

Differential Scanning Calorimetry (DSC) of the microbial composite films is determined based on ISO 11357-1 standard method using DSC Q200 (TA Instruments, U.S.A). The samples of microbial composite films are prepared by cutting the films into smaller pieces that are loaded onto the sample pan. The mass of samples are

5.7 Properties/Testing of Microbial Composite Films

57

Fig. 5.12 Microbial composite film after water absorption process

between 5 and 10 mg. Before the analysis begins, the mass of the samples are entered into the computer. After which, the sample and a control are treated to a temperature programme. The temperature of the sample and the temperature differential between sample and reference/control are the properties that are actually measured. The heat flow differential between sample and reference are calculated from the raw data signals. Figure 5.13 shows DSC Q200 (TA Instruments, U.S.A).

Fig. 5.13 DSC Q200 (TA Instruments, U.S.A)

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5.7.1.8

5 Biocoating Evaluation Techniques

Thermogravimetric Analysis (TGA)

The Thermogravimetric Analysis (TGA) of the microbial composite films is determined based on ISO 11358 standard method using TGA/DSC 1 (Mettler Toledo, U.S.A). The samples of microbial composite films are prepared by cutting the films into smaller pieces that are loaded onto the sample pan. The mass of samples are in the range of 5–10 mg. The analysis is performed by gradually raising the temperature of a sample in a furnace. Mass loss is observed if a thermal event involves loss of a volatile component. Figure 5.14 shows TGA/DSC 1 (Mettler Toledo, U.S.A).

Fig. 5.14 TGA/DSC 1 (Mettler Toledo, U.S.A)

5.7 Properties/Testing of Microbial Composite Films

5.7.1.9

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Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX)

Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) of the microbial composite films is determined using FEI Quanta FEG 650 (Thermo Scientific, U.S.A.). The surface, as well as the cross-sectional morphologies of the microbial composite films, are observed by using the scanning electron microscopy (SEM) analysis (Santana and Kieckbusch 2013). A sample of microbial composite films with dimension of 1 × 1 cm is prepared and mounted onto stubs and sputter coated with platinum in a turbo-pumped sputter coater. The surface area, cross-sectional morphologies and microstructure of each film product are observed and photographed using an SEM. Simultaneously, the basic elements of the microbial composite films are determined through Energy-Dispersive X-Ray Spectroscopy (EDX). Figure 5.15 shows FEI Quanta FEG 650 (Thermo Scientific, U.S.A.).

5.7.2 Chemical Analysis 5.7.2.1

Fourier-Transform Infrared Spectrometry (FTIR)

Fourier-Transform Infrared (FTIR) Spectrometry of the microbial composite films is determined based on Attenuated total reflectance—Fourier transforms infrared (ATR-FTIR) spectroscopy method using an IRPrestige-21 (Shimadzu, Japan). Samples of microbial composite film were loaded on the sample platform and the compression tip was adjusted in contact with the sample before analysis began. Figure 5.16 shows IRPrestige-21 (Shimadzu, Japan).

5.7.3 Microbial Analysis 5.7.3.1

Microbial Viability Testing

The microbial viability of microbial composite films is performed by using the contact plate method. The samples of microbial composite films are cut using a hole puncher with a diameter of 6 mm. The cut films are then sterilized in the laminar flow hood under UV light exposure for 30 min to ensure the surface contaminants of the films are sterilized thoroughly. Subsequently, respective cut films were transferred into different nutrient agar plates followed by incubation for 24 h at 37 °C.

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Fig. 5.15 FEI quanta FEG 650 (Thermo Scientific, U.S.A.)

5.8 Conductivity and Moisture Content Improvement of Microbial Composite Films The microbial composite films are further improved by increasing the conductivity and moisture content using metal ions and glycerol.

5.8.1 Improving the Conductivity of Films The conductivity of microbial composite films is improved since conductivity has influence on plant growth. The aim of the experiment is achieved by two approaches,

5.8 Conductivity and Moisture Content Improvement of Microbial …

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Fig. 5.16 IRPrestige-21 (Shimadzu, Japan)

biosorption of metal ions by Bacillus subtilis and mixture of microbial composite solution with metal ions. The metal ions used in this experiment are Copper Cu2+ ), Aluminium (Al3+ ) and Zinc (Zn2+ ). These three metal ions are chosen as they are the ten most conductive metal ions and are economical.

5.8.1.1

Biosorption of Metal Ions by Bacillus subtilis

Bacillus subtilis is cultivated in Penassay broth together with different concentrations of metal ions, 3, 6, 9, 10, 20 and 30 ppm. After 22 h of cultivation (log phase cultivation time frame), the culture is harvested, centrifuged and freeze-dried to obtain the powdered cell mass similar to the processes mentioned earlier. The microbial composite films are then fabricated and the conductivity analysis is carried out using the four-point-probe measurement method to record their conductivity.

5.8.1.2

Mixture of Microbial Composite Solution with Metal Ions

The microbial composite solution (150 mL solution contain 2 g sodium alginate with 0.5 g Bacillus subtilis) is mixed with different concentrations of metal ions, 3, 6, 9, 10, 20, 30, 40, 50 and 60 ppm. The microbial composite film is then fabricated and conductivity analysis is carried out using four-point-probe measurement method to obtain their conductivity.

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5.8.2 Improving the Moisture Content of Films A mixture of microbial composite solution with 40 ppm of copper ions solution (best conductivity concentration) is mixed with 0.5, 1, 1.5, 2, 3, 4, 5, 6 and 7% of glycerol. Glycerol is added to analyze the moisture content changes of/in the film over time, since it also helps plants develop healthier and stronger roots that boost their productivity. The microbial composite film is then fabricated the conductivity analysis is carried out using a four-point-probe measurement method to obtain their conductivity.

5.9 Fertilizer Coating The coating of fertilizer is performed by using the immersion method (Lubkowski et al. 2019). Standardized 6 × 6 mm fertilizers were coated with sodium alginate and microbial composites via two different techniques, namely, brief drying technique and overnight drying technique. The thickness of the coating is examined using a light microscope CX 41 (Olympus, Japan) under 400 × magnification. Figure 5.17 shows light microscope CX 41 (Olympus, Japan).

Fig. 5.17 Light microscope CX 41 (Olympus, Japan)

5.10 Planting of Water Spinach

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5.9.1 The 30-Min Drying Technique The coated fertilizers via immersion method are crosslinked in a 2% CaCl2 solution for 2 min. The fertilizers are then dried in an oven at 40 °C for 30 min to remove the surface moisture of the coating. For one layer of coating on fertilizers, the fertilizers were left to dry until the coating is completely dried. For two layers of coating on fertilizers, after 30 min of drying in the oven to remove surface moisture, the fertilizers were coated with a second layer of coating followed by crosslinking for 2 min. The fertilizers are then left to dry in the oven until the coatings are completely dried. Same steps were repeated until the desired layers of coatings are achieved.

5.9.2 The 24-h Drying Technique The coated fertilizers via immersion method are crosslinked in 2% CaCl2 solution for 2 min. The fertilizers are then dried in an oven at 40 °C for 24 h to completely remove moisture of the coating. For single layer of coating on fertilizers, the fertilizers were left to dry until the coating is completely dry. For double-layer coating on fertilizers, after complete 24-h drying in the oven to remove moisture, the fertilizers were coated with second layer of coating followed by crosslinking for 2 min. The fertilizers were then left to dry in the oven until the coatings are completely dry. The same steps were repeated until the desirable layers of coatings were achieved.

5.10 Planting of Water Spinach Experimental study of planting water spinach using uncoated and coated fertilizers is carried out to determine the effects of uncoated and coated fertilizers (with different thickness of coating) on the growth of plants. Black polybag with dimensions of 5-in. width × 7-in. length is filled with 500 g of soil. Each polybag is planted with one water spinach seed and left to grow for 7 days. On Day 8, one gram of fertilizer is applied on the surface of the soil around the plant. In this study, the plants (triplicate) are supplied with uncoated fertilizer, sodium alginate coated fertilizer and microbial composite coated (single-layer coating and double-layer coating) fertilizer. The same set of polybags was prepared without planting water spinach. Throughout the 30day study, the same volume of water was supplied to each polybag according to the growth of plants. Plant growth analysis and soil nutrients analysis were performed in this study.

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5.10.1 Plant Growth Analysis Plant growth analysis study was performed to record the changes of plants over time. In this study, plant growth analysis is required to explain the differences in plant growth within a species growing in different conditions. The analysis includes plant height, number of leaves, size of leaves, plant mass, specific leaf area, absolute growth rate and relative growth rate. Figure 5.18 shows the planting of water spinach at Day 25 from top view.

5.10.1.1

Plant Height

The height of the plant is measured with a tape measure (cm) from ground level. The plant was measured from its base to its highest point. Measurement should not be measured from the top of the soil as the soil may condense with watering over time.

5.10.1.2

Number of Leaves

Every visible leaf on the plant, including the tips of new leaves just beginning to emerge, are counted and recorded.

Fig. 5.18 Planting of water spinach, day 25, top view

5.10 Planting of Water Spinach

5.10.1.3

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Size of Leaves

The size of leaves is determined mainly on the length and width of the plants. In this study, the largest leaf of the plant was measured. The length of the leaf was measured with tape from the bottom to the tip of the leaf. While for the width of the leaf, was measured at its widest part.

5.10.1.4

Plant Mass

A trowel is used to gently extract the plants from the soil around the sides of the polybag. The dirt or soil clumps around the plant are gently removed and returned to its original location. A moderate stream of water is used to clean the soil from the roots. After which, the plant is dried with a paper towel. The plant is then placed on a scale and its weight is recorded. By reducing dirt dispersion in the polybag, the plant is then returned to its pot/bag and covered with soil. Finally, according to the experimental design, the plant is irrigated with an appropriate amount of water.

5.10.1.5

Specific Leaf Area

The leaves were traced on a graph paper and the squares covered were counted to estimate of the surface area for each leaf.

5.10.1.6

Absolute Growth Rate

Absolute growth rate is used to measure the net growth per unit time of a plant. The equation for the absolute growth rate is as below. W2 − W1 T

(5.2)

where W 1 = first weight of plant (eg: Day 1). W 2 = second weight of plant (eg: Day 2). T = the number of days between each measurement.

5.10.1.7

Relative Growth Rate

Relative growth rate is used to measure the productivity of a plant, which could be defined as the increase in dry mass per unit of plant mass over a specified period of time. The equation for the absolute growth rate is as below.

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lnW 2 − lnW1 t2 − t1

(5.3)

where W 1 = Initial dry weight of plant at time t 1 . W 2 = Final dry weight of plant at time t 2 .

5.10.2 Microbial Analysis of Microbial Composite Coated Fertilizers on Soils The microbial viability of microbial composite coated fertilizers on soils is performed by using the principle of streak plate method. This experiment is carried to test the presence of Bacillus subtilis and its microbial viability in the soil after applying the microbial composite coated fertilizers on soil. All steps in this study are carried using aseptic technique. The same amount of soil that were used in the experiment of plant growth analysis were first autoclaved in a beaker covered with an aluminium foil. The microbial composite coated fertilizers were first sterilized in the laminar flow hood under UV light exposure for 30 min to ensure the surface contaminants of the films are sterilized thoroughly. Subsequently, same amount of microbial composite coated fertilizers (single-layer microbial composite coating and double-layer microbial composite coating) used in the planting of water spinach were transferred to the autoclaved soil using aseptic technique in a laminar flow hood. Same volume of water is supplied to the fertilizers. Microbial viability testing is first performed by taking the autoclaved soil samples with sterile distilled water and then spread on the prepared nutrient agar. Following that, it is incubated for 24 h at 37 °C. Same steps were repeated the next day by taking soil samples from four-inch depth of the soils. The experiment is carried out for 23 days as in the plant growth analysis study, the fertilizers are applied to the soils only after one week, on Day 8 and the study stopped on Day 30.

5.10.3 Soil Nutrients Analysis The soil nutrients analysis is performed by taking soil samples from the soil every two days. The soil taken is approximately 4 inches from the soil surface by using a cork borer. The soil nutrient analysis involved in this study included nitrogen (N), phosphorus (P), potassium (P) and copper (Cu).

5.10.3.1

Nitrogen (N)

The nitrogen content of soil is determined using Nitrogen, Ammonia, Method 8038. 500 mg of soil sample is digested with 10 mL concentrated sulphuric acid

5.10 Planting of Water Spinach

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(H2 SO4 ). The sample is then syringe filtered and 1 mL sample is transferred to a 50 mL volumetric flask. The sample is topped up with 50 mL with deionized water. Then, three drops of mineral stabilizer is added and mixed well, followed by three drops of polyvinyl alcohol and mixed well. After that, 1 mL of Nessler reagent is added and mixed well. The nitrogen content is determined by reading the sample using Programme 380 N, Ammonia, Ness, Spectrophotometer DR 2800. Blank was prepared by using only deionized water in the steps described above.

5.10.3.2

Phosphorus (P)

Phosphorus content of the soil is determined using Phosphorus, Reactive (Orthophosphate), Method 8048. 500 mg of soil sample is digested with 10 mL concentrated sulphuric acid (H2 SO4 ). The sample is then syringe filtered and 1 mL sample was topped up with 10 mL with deionized water. PhosVer 3 Phosphate Reagent Powder Pillow is added into the sample cell. The sample cell was closed immediately and shook vigorously for 20–30 s. Then, the sample cell was left for a two-minute reaction. Blank was prepared by using only deionized water in the steps described above. The phosphorus content was determined by reading the sample using Programme 490 P React. PP in Spectrophotometer DR 2800.

5.10.3.3

Potassium (K)

Potassium content of the soil is determined using Atomic Absorption Spectroscopy (AAS) ASC-7000 (SHIDMADZU, Japan). 500 mg of soil sample is digested with 10 mL concentrated sulphuric acid (H2 SO4 ). The sample is then syringe filtered and 1 mL sample was topped up with 10 mL in a 15-mL falcon tube for analysis in AAS. Standard was prepared with 0, 0.1, 0.5 and 1.0 ppm potassium standard solution. Figure 5.19 shows the Atomic Absorption Spectroscopy ASC-7000 (SHIDMADZU, Japan).

5.10.3.4

Copper (Cu)

Copper content of the soil is determined using Atomic Absorption Spectroscopy (AAS) ASC-7000 (SHIDMADZU, Japan). 500 mg of soil sample is digested with 10 mL concentrated sulphuric acid (H2SO4). The sample is then syringe filtered and 1 mL sample was topped up with 10 mL in a 15-mL falcon tube for analysis in AAS. Standard was prepared with 0, 1.0, 2.0 and 4.0 ppm copper standard solution.

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Fig. 5.19 Atomic absorption spectroscopy ASC-7000 (SHIDMADZU, Japan)

5.11 Microbial Analysis of Fertilizer Coated with Microbial Composite Film The microbial analysis of is performed in an aseptic condition. The same amount of soil used in planting of water spinach (500 g) is loaded in a beaker and covered with an aluminium foil. The beaker is autoclaved to kill all possible microorganisms in the soil. After cooling, one gram of fertilizer coated with microbial composite film (single-layer coating) is applied on the top of the soil. Ten mL of water was added to the soil and the soil sample was taken from approximately 4-in depth of the soil. The soil sample is mixed with sterile distilled water and then streaked on a nutrient agar plate using an inoculating loop. Autoclaved soil before the application of fertilizers is also proceeded with microbial analysis to ensure that there were no other microorganisms present in the soil. Same procedure was applied to another experiment that used fertilizers with 2-layer microbial composite film.

References

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5.12 Mathematical Modelling/Simulation Mathematical modelling and simulation can be formulated to represent the process of nutrients transfer from fertilizers to plants. The model could be used to explain the empirical process better.

5.12.1 Mathematical Modelling/Simulation on Soil Nutrients Analysis Mathematical modelling can be simulated based on the results of soil nutrient analysis. Differential mass balances on the nutrient transfer from fertilizers to soil and plants can be formulated. Further integration of model can also be derived and validated by using MATLAB and Polymath software.

References H.P.S. Abdul Khalil, Y.Y. Tye, Z. Ismail, J.Y. Leong, C.K. Saurabh, T.K. Lai, E.W. Ni Chong, P. Aditiawati, P.M. Tahir, R. Dungani, Oil palm shell nanofiller in seaweed-based composite film: mechanical, physical, and morphological properties. BioResources 12(3), 5996–6010 (2017). https://doi.org/10.15376/biores.12.3.5996-6010 B. Afreen, N.R. Nouman Rasoo, I. Saima, Characterization of plastic degrading bacteria isolated from landfill sites. Int. J. Clinic. Microbiol. Biochem. Technol. 4(1), 30–35 (2020). https://doi. org/10.29328/journal.ijcmbt.1001013 K. Lubkowski, A. Smorowska, M. Sawicka, E. Wróblewska, A. Dzienisz, M. Kowalska, M. Sadłowski, Ethylcellulose as a coating material in controlled-release fertilizers. Pol. J. Chem. Technol. 21(1), 52–58 (2019). https://doi.org/10.2478/pjct-2019-0010 J.W. Rhim, Physical and mechanical properties of water resistant sodium alginate films. LWT Food Sci. Technol. 37(3), 323–330 (2004). https://doi.org/10.1016/j.lwt.2003.09.008 A.A. Santana, T.G. Kieckbusch, Physical evaluation of biodegradable films of calcium alginate plasticized with polyols. Braz. J. Chem. Eng. 30(4), 835–845 (2013). https://doi.org/10.1590/ S0104-66322013000400015 J.T. Trevors, Sterilization and inhibition of microbial activity in soil. J. Microbiol. Meth. 26(1–2), 53–59 (1996). https://doi.org/10.1016/0167-7012(96)00843-3

Chapter 6

Conclusions

In conclusion, it is clearly seen that biocoatings have the potential to reduce environmental issues while maintaining existing yields of a variety of agricultural and plantation crops. Biocoatings are expected to enhance the demand for biofertilizers in the future since they replenish the mostly depleted microbiome in conventional agriculture, resulting in agroecosystem sustainability. It also aids in reduction of environmentally detrimental subsidies such as expensive chemical fertilizers, resulting in more cost-effective agricultural output. Biofertilizer inoculation is a potential approach for increasing crop yields while reducing inorganic fertilizer coating consumption, resulting in environmentally benign, long-term agriculture. Agriculture is vital to a country’s economic well-being. Inorganic fertilizer coating is used on a vast scale in modern intensive agriculture methods to improve crop production and meet the nutritional needs of the world’s growing population. Rapid urbanization, combined with shrinking agricultural lands, dramatic changes in climatic conditions and widespread use of agrochemicals in agricultural practises, has been found to cause environmental disruptions and public health hazards, threatening food security and agriculture sustainability. Aside from that, indiscriminate inorganic coating usage is causing farm soils to lose their quality and physical qualities, as well as their chemical and biological health. Plant-associated microorganisms, with their plant growth-promoting properties, when incorporated with fertilizer coating as biocoatings, offer immense potential to address these issues and play a key role in increasing plant biomass and agricultural output in greenhouse and field environments. Increased nutrient availability such as nitrogen (N), phosphorus (P), potassium (K), phytohormone regulation, biocontrol of phytopathogens and amelioration of biotic and abiotic stressors are all favourable processes for plant growth. This plant–microbe interaction available from biocoatings is critical for long-term agricultural sustainability and these bacteria may play an important role as an ecological engineer in reducing the usage of chemical fertilizers. Inoculum preparation, incorporation of cell protectants such as glycerol, lactose and starch, a good carrier

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 H. A. Tajarudin and C. W. C. Ng, Biocoating for Fertilizer Industry, SpringerBriefs in Applied Sciences and Technology, https://doi.org/10.1007/978-981-19-6035-2_6

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material, proper packing and optimal distribution techniques are among the procedures involved in the creation of solid-based or liquid biocoated-fertilizer formulation. Entrapment/microencapsulation, nano-immobilization of microbial bioinoculants and biofilm-based biofertilizers are also new formulation advancements. As a result, inoculation with beneficial bacteria has emerged as a cutting-edge, environmentally acceptable solution for feeding the world’s population with limited resources. It is crucial to have state-of-the-art on the use of microbial strains in the biocoatings of fertilizers in various agricultural systems for sustainable agriculture, soil fertility maintenance and crop productivity enhancement. Acquisition of advanced knowledge of plant-bacteria interactions, as well as bioengineering of microbial communities to improve the performance of biofertilizers in field conditions, is thought to aid in the development of strategies for sustainable, environmentally friendly and climate-smart agricultural technologies to deliver short and long-term solutions for increasing crop productivity and feeding the world more sustainably.