Applications of Chitan and Chitosan

Mattheus F. A. Goosen

• Publisher: CRC Press
• Year: 2020
• Print ISBN:
  9781138454828
• Edition: 1
• eBook ISBN:
  9781000154368
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

The main driving force behind the development of new applications for chitin and its derivative chitosan lies with the fact that these polysaccharides represent a renewable source of natural biodegradable polymers. Since chitin is the second most abundant natural polymer, academic as well as industrial scientists are faced with a great challenge to find new and practical applications for this material. This book provides an examination of the state of the art, and discusses new applications as well as potential products. Applications of Chitin and Chitosan deals almost exclusively with applications. Previous books in the field have devoted less than 30% of their material to commercial or medical uses.
In the past thirty years, substantial progress has been made on fundamental and applied research in chitosan technology. One of the driving forces behind this rapid development has been the decrease in the supply of natural resources. At the same time there has been an increased realization that there are abundant alternative bioresources. Two factors-economics and versatility-have also stimulated interest in chitosan's utilization in various fields. Chitin and chitosan derivatives have applications in fields that range from fertilizers to pharmaceuticals. Chitosan is no longer just a waste by-product from the seafood processing industry. This material is now being utilized by industry to solve problems and to improve existing products, as well as to create new ones.Applications of Chitin and Chitosan is illustrated with over 100 photos, charts, graphs and figures and more than 40 tables.
Applications of Chitin and Chitosan will be of interest to industrial personnel involved in bioprocessing as well as bioengineering students, specialists in the biomedical and biopharmaceutical industry, biochemists, food engineers, environmentalists, and microbiologists and biologists who specialize in chitosan technology. Publication: Fall 1996.

Overview

CHAPTER 1

Applications and Properties of Chitosan

Q. Li, E. T DUNN, E. W. GRANDMAISON, AND M. F. A. GOOSEN^*

Department of Chemical Engineering Queen’s University Kingston, Ontario, Canada K7L 3N6

INTRODUCTION

Chitosan is a polysaccharide obtained by deacetylating chitin, which is the major constituent of the exoskeleton of crustaceous water animals. This biopolymer was traditionally used in the Orient for the treatment of abrasions and in America for the healing of machete gashes [1]. A recent analysis of the varnish on one of Antonio Stradivarius’s violins showed the presence of a chitinous material [2]. Chitosan was reportedly first discovered by Rouget in 1859 [3] when he boiled chitin in a concentrated potassium hydroxide solution. This resulted in the deacetylation of chitin. Fundamental research on chitosan did not start in earnest until about a century later. In 1934, two patents, one for producing chitosan from chitin and the other for making films and fibers from chitosan, were obtained by Rigby [4,5]. In the same year, the first X-ray pattern of a well-oriented fiber made from chitosan was published by Clark and Smith [6]. Since then, knowledge about chitosan has been greatly advanced by the work of such pioneers as Muzzarelli [3]. The main driving force in the development of new applications for Chitosan lies in the fact that the polysaccharide is not only naturally abundant, but it is also nontoxic and biodegradable. Unlike oil and coal, chitosan is a naturally regenerating resource (e.g., crab and shrimp shells) that can be further enhanced by artificial culturing. It was reported that chitosan and chitin are contained in cell walls of fungi [7,8]. Chitin, however, is more widely distributed in nature than chitosan and can be found in mushrooms, yeasts, and the hard outer shells of insects and crustaceans. It was reported, for example, that about 50–80% of the organic compounds in the shells of crustacea and the cuticles of insects consists of chitin [3]. At present, most chitosan in practical and commercial use comes from the production of deacety-lated chitin with the shells of crab, shrimp, and krill (the major waste by-product of the shellfish-processing industry) being the most available sources of chitosan [9,10].

One of the most useful properties of chitosan is for chelation. Chitosan can selectively bind desired materials such as cholesterol, fats, metal ions, proteins, and tumor cells. Chelation has been applied to areas of food preparation, health care, water improvement, and pharmaceutics. Chitosan has also shown affinity for proteins, such as wheat germ agglutinin [11] and trypsin [12]. Other properties that make chitosan very useful include inhibition of tumor cells [13], antifungal effects [14], acceleration of wound healing [15,16], stimulation of the immune system [17, 18, 19], and acceleration of plant germination [20].

Chitosan is a good cationic polymer for membrane formation. In early research it was shown that membranes formed from the polymer could be exploited for water clarification, filtration, fruit coating, surgical dressing, and controlled release. In 1978, for example, Hirano showed that N-acetyl chitosan membranes were ideal for controlled agrochemical release [21]. Later, he found that a semipermeable membrane with a molecular weight cutoff ranging from 2,900 to 13,000 could be formed [22] from chitosan. In 1984, Rha et al. first documented a procedure for preparing chitosan capsules for cell encapsulation [23]. The chitosan-alginate capsules had a liquid alginate core. Since then, several other studies have been reported on the use of chitosan copolymers for immobilization of hybridoma cells and plant cells [24,25]. However, the apparent poor biocompatibility of chitosan with hybridoma and insect cells was indicated by Smith et al. [26] and McKnight et al. [27].

This chapter focuses on various applications of chitosan, as well as current research on its physicochemical properties. Application areas that are covered include water treatment, pharmaceutics, biotechnology, food processing, and membranes.

PHYSICOCHEMICAL PROPERTIES OF CHITOSAN

Chitosan is a collective name given to a group of polymers deacetylated from chitin. The difference between chitin and chitosan lies in the degree of deacetylation. Generally, the reaction of deacetylating chitin in an alkaline solution cannot reach completion even under harsh treatment. The degree of deacetylation usually ranges from 70% to 95%, depending on the method used. These methods have been thoroughly reviewed by Muzzarelli [28]. The technique of Horowitz, for example, treating chitin with solid potassium hydroxide for 30 minutes at 180 °C, results in the highest removal (95%) of acetyl groups. Recently, Kobayashi et al. [29] published a procedure for preparing chitosan from mycelia of absidia strains. A chitosan product with 79–91% deacetylation and 1,200,000 molecular weight was obtained. Most publications use the term chitosan when the degree of deacetylation is more than 70%.

Up to now, only a few studies on the molecular conformation of chitosan have been reported. There is still no one simple model describing chitosan, in spite of the fact that several models have been published for chitin, α-chitin [30] and β-chitin [31]. The α-chitin, for example, is tightly arranged in an antiparallel fashion, whereas β-chitin is in a parallel form. An analysis of the diffraction spectra of chitin and chitosan revealed a structural resemblance between the two polymers [28]. It has been suggested that the conformation of chitosan was similar to that of α-chitin [32].

Commercial chitosan is mainly produced by deacetylating chitin obtained from seashell materials. The quality and properties of chitosan products, such as purity, viscosity, deacetylation, molec...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Preface
• Part I: Overview
• Part II: Structure and Properties
• Part III: Food and Agriculture
• Part IV: Medicine and Biotechnology
• Part V: Textiles and Polymers
• Part VI: Wastewater Treatment
• Index