Kitin

Kitin, commonly known in English as chitin, is a natural biopolymer made of long chains of N-acetylglucosamine linked by β-(1→4) glycosidic bonds. It forms semi-crystalline fibrils and is the second most abundant biopolymer in nature after cellulose. Kitin is a major structural component of the exoskeletons of arthropods, including insects, arachnids, and crustaceans, as well as the cell walls of fungi.

Biosynthesis occurs via chitin synthase enzymes that polymerize N-acetylglucosamine units, which assemble with proteins and minerals to meet structural needs. Industrially, kitin is typically extracted from chitin-rich biomass such as crustacean shells through demineralization and deproteinization. Purified kitin can be converted to chitosan by deacetylation, producing a more soluble polymer with similar biocompatibility.

Kitin and its derivatives have a wide range of applications due to biocompatibility, biodegradability, and non-toxicity. They are used in biomedicine (wound dressings, tissue scaffolds, drug delivery), agriculture (biostimulants, seed coatings, disease resistance), and environmental technologies (water treatment, filtration, sorption of metals and dyes). Film-forming and coating applications also exist, including biodegradable coatings for packaging and specialty membranes.

In some languages, kitin is the term for chitin, reflecting its widespread occurrence across biology and industry.