Marine chitin upcycling with immobilized chitinolytic enzymes: current state and prospects

Chitinases, beta-N-acetylglucosaminidases, chitin deacetylases and chitosanases enable ecofriendly enzymic conversion of chitin and its derivative, chitosan, into low-molecular weight sugars known as chitooligosaccharides (COSs). Based on their origin, COSs are biocompatible natural compounds with pronounced biological activity and are promising green precursor materials for biomedical, pharmaceutical and other biotechnological applications of high market and social value. In pioneering attempts, chitinolytic enzymes were used in free form in reactors for chitin and/or chitosan degradation, but poor enzyme stability and the difficulty of recycling the biocatalyst at the end of the process were identified as significant technological drawbacks. More recently, enzyme immobilization on macro- or microscopic carrier particles was attempted, in order to improve protein stability and recovery. In this tutorial review, fundamental aspects of enzyme immobilization on feasible carrier systems are described and state-of-the-art applications of the methodology for sustainable biocatalytic processing of chitin and chitosan biomass into chitosugar-based speciality chemicals are summarized.