Occurrence of Chitin

Chitin is a widely distributed polysaccharide in nature. Its estimated production is 10¹⁰ to 10¹² tons per year. The primary sources are sea animals, insects, fungi, and micro-organisms. Chitosans, which are associated with some fungal cell walls and green algae, are found less frequently in the biosphere. This chapter describes how chitin forms complex composites. In the exoskeleton, which covers all arthropods and consists of mineralized fibrous chitin-based tissues, there are thickened areas where the chitin supplies the tensile strength; the hardness and resistance to compression are provided by materials such as minerals or solid proteins.