2. Chitosan structures and physicochemical characteristics
Chitin and chitosan are co-polymers of N-acetyl-d-glucosamine and d-glucosamine, where the ratio of each monomer in the polymer chain defines its physical, chemical and biological properties, and whether it is characterized as chitin or chitosan. The N-acetyl-d-glucosamine and d-glucosamine residues in chitin and chitosan are linked together via β-1,4-glycosidic linkages similar to cellulose. Although chitin can be found in various sources in nature, it is normally produced from shrimp or crab shells by demineralization and deproteinization ( Rinaudo, 2006 and Younes and Rinaudo, 2015).