Applications of chitin and chitosan as natural biopolymer: potential sources, pretreatments, and degradation pathways

Chitin (CT) and its deacetylated derivative, chitosan (CS), are globally available in large quantities mostly found in marine and freshwater ecosystems as a waste generated from the exoskeletons of seafood. Thus, the motivation of present review is to identify the global waste generation of CT/CS and its evaluation as a potential feedstock for various applications. The potential sources of CT, extraction strategies for CS, and various properties of CS with enzymatic degradation pathways are elucidated. The major challenges (such as management, degradability, and inhibitors production) associated with conversion of polysaccharides rich substrates (CT/CS) into biofuels are covered. The pretreatments (such as mechanical, physical, chemical, and biological) to improve the performance of CT/CS to biofuels is deliberated. The addition of CS in the mono-anaerobic digestion improved the biogas production. However, approaches such as co-digestion or/and biochar addition can decrease the level of inhibitors and enhance the biogas production. The CT can be used also for bioethanol production by fermentative microbes (such as Saccharomyces cerevisiae and Candida albicans ). The use of saccharide rich substrates (such as seafood having CT) in AD and fermentation with the applications of pretreatments could be a potential approach to enhance biofuels recovery. The generation of bioenergy products would decrease the sea waste and protect environmental health. Graphical abstract