16 - Chitin and chitosan from marine by-products

Abstract

Publisher Summary Chitin is a major component of the exoskeleton of invertebrates, crustaceans, insects, and the cell wall of fungi and yeast, and acts as a supportive and protective component. It is the second most abundant natural polymer on Earth after cellulose. Chitin is biosynthesized from polymerization of uridine diphosphate-N-acetyl-D-glucosamine by chitin synthase. Chitosan, a copolymer of mainly D-glucosamine and a small proportion of N- acetyl-D-glucosamine with β-linkage, is obtained by alkaline or enzymatic deacetylation of chitin and is also an abundant polymeric product in nature. This chapter discusses the chemistry and uses of chitin, chitosan, and their oligomers. Both chemical and enzymatic methods are known for preparation of chitin, chitosan, and their oligomers, with different degrees of deacetylation, polymerization, and molecular weight. Chitin, chitosan, and their oligomers can be produced chemically using concentrated HCl followed by column chromatographic fractionation. Three methods are known for the modification of the process of isolation of chitin and chitosan oligomers. These are acetolysis, fluorohydrolysis, and sonolysis. Chitin and chitosan oligomers can be prepared through microbiological and fungal treatments. Chitin and chitosan may be degraded by certain enzymes such as chitinases and chitosanases respectively, and the process is environmentally friendly. They are used in food preservation such as for seafood or fruits, as well as for acidity adjustment, and as antibacterial and antifungal agents.