Chitin and Chitosan

Abstract Chitin is a structural polysaccharide widely found in nature. It occurs as highly ordered microfibrils in many species, such as yeast, fungi, insects, and marine invertebrates. Chitin is a homopolymer of 1‐4‐linked 2‐acetamido‐2‐deoxy‐β‐ d ‐glucopyranose, although some of the glucopyranose residues are deacetylated and occur as 2‐amino‐2‐deoxy‐β‐ d ‐glucopyranose. When chitin is deacetylated to more than 50% as the free amine form, it is referred to as chitosan. Biopolymerization of chitin is via the activated monomer N ‐acetyl‐uridine diphosphate (UDP)‐glucosamine by synthase enzymes. The isolation of chitin is commonly from the shell fish waste of the shrimp and crab industries. Chitin is not soluble in any common solvents, while chitosan is dissolved in many common aqueous acid solutions. Industrially, chitin is mainly used as a powder and as a precursor to chitosan. Applications of chitosan are found in many primary industries, such as agriculture, paper, textiles, cosmetics, and waste water treatment. Chitosan has good film‐ and fiber‐forming properties. Many potential medical and pharmaceutical uses of chitosan have been described. It has also become a popular nutritional dietary additive.