Polysaccharides: Chitin and Chitosan: Chemistry and Technology of Their Use As Structural Materials

Abstract

Chitin is considered the second most plentiful organic resource on the earth next to cellulose, and is present in marine invertebrates, insects, fungi and yeasts. Chitin is essentially a homopolymer of 2-acetamido-2-deoxy-$β$-D-glucopyranose, although some of the glucopyranose residues are in the deacetylated form as 2-amino-2-deoxy-$β$-D-glucopyranose. When chitin is further deacetylated to about 50% it becomes soluble in dilute acids and is referred to as chitosan. Thus chitosan is the N-deacetylated derivative of chitin, although the N-deacetylation is almost never complete. There is not a sharp boundary in the nomenclature distinguishing chitin from chitosan. Chitin does occur in nature in the fully acetylated form and has been referred to as chitan [1]. Chitosan rarely occurs in nature, but is found in the dimorphic fungus, Mucor rouxii [2]. Its occurrence in Mucor rouxii is via the enzymatic deacetylation of chitin.