Chitin from a zero-waste shrimp shell biorefinery as a building block for advanced sustainable materials

Chitin is the second most abundant natural polysaccharide, found naturally as a structural biopolymer in the exoskeletons of crustaceans and insects and in the cell walls of fungi. It is composed of linear chains of beta-(1-->4)-linked N-acetyl-D-glucosamine units that assemble at the nano- and microscale into hierarchical crystalline microfibrils. Chitin and its deacetylated derivative chitosan are promising biobased polymers for diverse applications owing to their tunable surface chemistry, versatility for chemical and physical functionalization, and favorable intrinsic biological properties, including antimicrobial activity, biocompatibility, and biodegradability. Furthermore, they can be directly isolated from crustacean shell waste generated by the seafood-processing industry, making them abundant, scalable, and renewable building blocks for the transition toward a sustainable circular bioeconomy. 
In this work, chitin was extracted from shrimp (Pandalus borealis) shell processing waste through a zero-waste green biorefinery strategy in which all major biomass fractions (astaxanthin, peptides, minerals and polysaccharydes) were recovered using green solvents and mild processing conditions. To expand its applicability as a functional polymer building block, the purified chitin was modified into chitin nanofibers (ChNF), which were then processed into self-standing films and lightweight foams. The purified chitin, ChNF and materials were comprehensively characterized with respect to their composition, crystalline structure, surface chemistry, nano/microscale morphology and mechanical and thermal behavior, to elucidate structure-property relationships and guide further material development.
Overall, this work demonstrates an integrated pathway for transforming shrimp shell residues into high-value renewable polymeric building blocks for versatile materials design, contributing to the development of next-generation sustainable polymer systems.