Comparative Review of Microbial Chitosanases: Properties, Structures, Hydrolytic Modes and Applications.

Chitosanases (EC 3.2.1.132) are glycoside hydrolases that specifically cleave β-1,4-glycosidic bonds within polysaccharides. In nature, they are predominantly produced by bacteria and fungi. These enzymes break down chitosan into low-molecular-weight chitooligosaccharides with enhanced bioavailability, acting as pivotal catalysts in the microbial carbon cycle. Variations in their hydrolytic mechanisms across microbial origins are crucial for tailoring bioactive chitooligosaccharides with defined structures and functions. This review, from the perspective of microbial diversity, synthesizes current knowledge on chitosanases, covering their enzymatic properties, structural features, substrate specificities, and hydrolytic modes, with particular emphasis on both shared features and origin-specific distinctions.Such insights will accelerate the discovery and in-depth characterization of microbial chitosanase resources and guide the rational engineering of enzymes for the precise and efficient synthesis of high-value chitooligosaccharides.