Chitin/chitosan: bioresources, applications field, production technologies

Abstract

The present review is devoted to such biotechnologically interesting polymers as chitin and chitosan, which form the cuticle of arthropods and the core of fungal cell wall. Chitosan is a linear polysaccharide containing D-glucosamine and N-acetyl-D-glucosamine residues, which has valuable biological properties. It is a product of deacetylation of chitin. Possessing pronounced muco-adhesive properties and controlled release ability, the chitosan is widely used in delivery of various therapeutic agents, such as anticancer drugs, antibiotics, proteins, nucleic acids, etc. Chitosan nanoparticles, micro- and nanocapsules, as well as hydrogels, can be developed for targeted delivery of drugs to specific organs and tissues. Initially, the attention of biotechnologists was focused on animal chitin, and basic methods for extracting and purifying this biopolymer took shape at this stage. Despite the complexity of the organization of the arthropod cuticle, the chitin in it is not covalently bound to other linear biopolymers and is organized into nanofibrils that form a fairly homogeneous matrix, therefore it is easier to extract than from the mycelium mass of fungi, where this biopolymer is tightly packed into microfibrils bound to the glucan matrix. The main stages of chitin extraction and its further modification into chitosan are deproteinization, demineralization, deacetylation, and the main methods of chitosan purification are filtration, dialysis and reprecipitation. After isolation, chitosan should be dried. To extract chitin from the fungi, the above classical chemical methods are often combined with the methods of “green chemistry” and industrial microbiology. The profitability of the production of chitin/chitosan from crustaceans and edible mushrooms is approximately at the same level. The cost of mushroom products can be reduced by using agricultural or forestry waste as nutrient substrates. This makes the use of fungi as sources of chitin/chitosan in forest regions rather promising.