Green technologies for bio-refinery in marine crustacean shell valorisation from chitin perspective

The surge in global seafood processing has led to a significant increase in by-products and side streams, including the shells of crustaceans like shrimp, crab, and lobster. These side-stream materials primarily consist of chitin and can be transformed into chitosan through deacetylation. These side-stream materials primarily containing CaCO3, protein, pigments and chitin, possess various high-valuable ingredients. Specially, chitosan transformed from chitin through deacetylation is commonly applied in a wide range of fields, especially as additives, dietary supplements, and packaging in food engineering. This review standing from the perspective of chitin, comprehensively presents the current advances in conventional chemical extraction technology and introduces the revolution of biotechnology such as protease reactions and microbial fermentation, green solvents, for example, ionic liquids (ILs) and deep eutectic solvents (DESs), and innovative novel processing technologies, including microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), plasma technology, subcritical water and supercritical treatment, pulsed electric field (PEF), high hydrostatic pressure (HHP), and electrochemistry extraction. Simultaneously, the recovery of protein and CaCO3 can be implemented together with chitin innovative demineralization and deproteinization to further enhance the valorisation of crustacean side streams. To release environmental impact, biorefinery technologies for chitin recovering from marine crustacean side streams have been developed and improved. Traditional processes are constrained by their high energy consumption, sequential processing, long duration, and limited product quality. Innovative extraction techniques show great potential in the recovery, purification, transformation and modification of chitin to serve the marine circular and sustainable economy.