Bacterial Cellulose

Synthesis, Production, and Applications

Sher Bahadar Khan, Tahseen Kamal, Sher Bahadar Khan, Tahseen Kamal

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000455632
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie de la chimie et de la biochimie

Bacterial cellulose (BC) is a natural polymer produced by different microbial cells. Its unique structural, physico-chemical, mechanical, thermal, and biological properties offer much potential for use in diverse applications in the biomedical, electronics, energy, and environmental fields, among others. This text provides an overview of the synthesis, characterization, modification, and application of BC. • Discusses sources, characterization, and biosynthesis of BC • Covers composites and aerogels based on BCs • Describes development of BCs from waste and challenges in large-scale production of BCs • Explores a variety of applications such as environmental, industrial, and biomedical This book will be of great interest to researchers and industry professionals in materials science, chemical engineering, chemistry, and other related fields seeking to learn about the synthesis and application of this important material.

1Bacterial Cellulose

History, Synthesis, and Structural Modifications for Advanced Applications

Atiya Fatima, Sumayia Yasir, Noor Qahoor, Tahseen Kamal, Mohd Shariq Khan, Shaukat Khan, Muhammad Wajid Ullah, Mazhar Ul-Islam, and Md Wasi Ahmad

DOI: 10.1201/9781003118756-1

CONTENTS

1.1 Introduction

1.2 Bacterial Cellulose

1.3 History and Synthetic Approaches

1.4 Microbial Synthesis

1.4.1 Advancements in Fermentation Approaches

1.4.2 Static Fermentative Cultivation

1.4.3 Shaking Fermentative Cultivation

1.4.4 Agitation Fermentative Cultivation

1.5 BC Structure

1.6 Need and Types of BC Structure Modification

1.7 Chemical Modification

1.7.1 Acid Hydrolysis

1.7.2 Enzymatic Hydrolysis

1.7.3 Modification with Polymers

1.7.3.1 BC-Chitosan

1.7.3.2 BC-Polyvinyl Alcohol

1.7.3.3 BC-Polydopamine

1.7.3.4 BC-Polypyrrole

1.7.3.5 BC-Polylactic Acid

1.7.3.6 BC-Polysaccharides Carboxymethyl Cellulose

1.7.4 Modification with Adsorbents

1.7.5 Modification with Nanoparticles

1.7.5.1 In situ Formation of BC-Nanocomposites

1.7.5.2 In situ Formation of Nanostructures through Reduction

1.7.5.3 In situ Formation of Nanostructures through Precipitation

1.7.5.4 In situ Formation of Nanostructures through Sol-Gel Reaction

1.7.5.5 Ex situ Introduction of Components

1.8 Selected Advanced Applications of Modified BC

1.9 Conclusions

1.10 Acknowledgment

References

1.1 Introduction

Biomaterials, including biopolymers, are receiving immense interest thanks to their abundance, natural synthesis, effective physicochemical features, and widespread applications. A number of polymers, including polysaccharides, polyamides, and polycarbonates, are being explored through multiple synthetic routes for exclusive applications (1). Bacterial cellulose (BC), also termed as biocellulose and microbial cellulose, is among the most prevalent emerging biopolymers because it has shown impressive structural, physicochemical, and mechanical features. Its high crystallinity, absorbing capabilities, porous geometry, biocompatibility, and post-synthetic modification features have led to advanced application in environmental, biomedical, pharmaceutical, food, packaging, catalysis, and electromagnetic fields (2, 105). Exploration of novel applications is continued together with new synthetic media and cost-effective BC production processes (3, 106).

The medical and environmental sectors are currently facing significant challenges. The modern era of industrialization has eased human life by offering advanced and diversified technologies, but it has greatly affected environmental quality by incorporating toxic and poisonous emissions into the atmosphere (4). The highly toxic or carcinogenic organic contaminants are potentially dangerous to human health, causing cancers, physical birth defects, and mental disorders. Various chemical or biological materials have been utilized for the effective removal or degradation of a wide range of toxic contaminants. In this context, carbon nanotubes (CNTs), graphene and biochar, and metal-based adsorbents and catalysts have been extensively explored as potent pollutant removal materials (5). Various biological materials such as cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), microfibrillated cellulose (MFC), and BC have emerged as environmentally friendly, cost-effective, and efficient materials for environmental applications.

As a matter of fact, pure materials lack certain important features, which restricts their applications in diverse fields. BC, despite its impressive biological, physical, and mechanical features, lacks antibacterial, magnetic, conducting, and antioxidant features. This lack consequently greatly reduces the applicability of BC in medical, environmental fields, in electromagnetic device synthesis and in the pharmaceutical industry. To cope with these limitations and add additional features to BC, its structure has been modified through various chemicals entities, including nanomaterials, polymers, acids, and alkalis (3, 6). The modified BC has shown tremendous enhancement in its physicomechanical and biological features and consequent applications in a variety of fields. The main factors contributing toward the structural modification of BC are its 3D porous geometry and availability of OH moieties. A number of materials have been combined with BC in the form of composites through inside, ex situ, and polymer blending techniques (2, 3). BC has been combined with chitosan, alginate, polyethylene glycol, polyaniline, silver oxides, zinc oxides, cobalt oxides, clay materials, natural products, and numerous other materials (2, 7). Indeed, every modification or composite development is achieved through a specific approach.

This chapter basically illustrates the BC structure, its synthetic pathways, production techniques, and various modifications made in its structure for enhanced applications. In upcoming sections, the main topics are all discussed in detail and are accompanied by a comprehensive literature study.

1.2 Bacterial Cellulose

BC is produced through a number of synthetic routes by various microbes, including bacteria, fungi, and algae (3). Glucose is the main precursor, whereas other sugars, including fructose and galactose, have also been converted to cellulose through multiple metabolic pathways. In recent years, a novel approach to developing BC through a cell-free enzymatic system has grabbed attention because it can eliminate the shortcomings associated with the cellular system (8, 9). Conventional BC is produced from synthetic media consisting of sugar and protein sources. However, considering the production cost, attention has shifted toward waste and naturally available cheap resources (10, 107). BC has been produced in various shapes; however, it is most commonly produced as BC sheets or pellicles on a media surface under a static cultivation strategy. BC appears as a gel-shaped semi-transparent structure consisting of microfibrils connected in a web-shaped structure (11). During microbial synthesis, specifically using a static cultivation strategy, BC is produced at the water-air interface, growing in the form of a gel and resulting in a thick sheet.

BC has exceptional physicomechanical features that include high crystallinity, water-holding capabilities, mechanical strength, nontoxicity, high porosity, moderate biocompatibility, biodegradability, and pre- and post-synthetic moldability (12, 13). The physical, mechanical, and biological properties of BC are better than those of plant cellulose are. The main precursor of BC production is glucose, but its production can be carried through a verity of monomer sugars, including fructose and galactose. Monosaccharides enter the bacterial body where, through series of enzymatic reactions, they are converted to cellulose chains. These chains come out of the bacterial cell wall through pores and unite through a hydrogen bonding interaction, forming microfiber ribbons and eventually a net-shaped sheet structure (14, 15).

BC has diverse applications, most prominently in wound healing, facial masks development, antimicrobial membranes, skin tissue repair, drug delivery, electronics, display devices, diaphragms, foods, and paper (16, 17). The biomedical field is the prime area for BC applications because of BC’s high biocompatibility, porous geometry, nontoxic nature, and chemical nature (18, 19). As mentioned earlier, applications using pure BC were restricted by its lack of certain important features.

Pure BC lacks antimicrobial, antioxidant, biocompatible, conducting, and magnetic properties that partially diminish its competencies in biomedical and electronic sectors (16). An approach developed to cope with such limitations is its structural modification with a variety of materials to develop composites. Numerous composites of BC with polymers and nanomaterials have been produced to overcome such deficiencies and enhance its biological activities, mechanical strength, conduction, magnetic properties, biocompatibility, transparency, and biomedical applications (16).

1.3 History and Synthetic Approaches

Bacterial cellulose is a natural polymer produced by various bacteria (such as Escherichia, Azotobacter, Agrobacterium, Rhizobium, Achromobacter, Aerobacter, Sarcina, Salmonella, and many cell-free systems) using numerous synthetic and nonsynthetic media (20–22). The first BC production was reported by A.J. Brown in 1886 using glucose as the main constituent; however, in time production was also reported from varied sugar sources (including galactose, fructose, and sucrose) (23). It is well established through numerous synthetic pathways that glucose and other sugars such as fructose are interconverted by enzymatic reactions. BC synthesis involves several routes differentiated by the different controlling enzyme, as illustrated in Figure 1.1. Bacterial species consume sugar media to formulate glucose chains, which protrude out of their bodies (in the form of an exoskeleton) to be combined through hydrogen bonding developing microfibrils. These fibrils then develop into a reticulated porous web bonded by inter- and intramolecular forces over the media surface. Reinforcement of new fibrils is made from the bottom, producing a cultivation is needed for scaffolds surface (21). To ramp up BC production, culture agitation is also employed, whereby strands of BC are produced...