Preparation of a crude chitosanase from blue crab viscera as well as its application in the production of biologically active chito-oligosaccharides from shrimp shells chitosan

Abstract

In this study, a digestive chitosanase from blue crab (Portunus segnis) viscera was extracted, characterized and applied. The crude chitosanase showed optimum activity at pH 4.0 and 60 °C and retained >80% of its activity over a pH range from 3.0 to 10.0. Subsequently, the crude chitosanase was applied to produce bioactive varying molecular weight (M_w) and acetylation degree chitosan-depolymerization products (CDP) with specially sequences composition determined by MALDI-TOF MS owing to an endo-cleavage mode. This hydrolysis process allowed to the preparation, after 24 h of incubation at 40 °C, of a low Mw water soluble CDP (H _24h, <4.4 kDa) with DP up to 6 and a high Mw CDP (C _24h, 142.19 kDa). Following their physicochemical characterization, the functional properties, antioxidant and antimicrobial activities of CDP were investigated. Interestingly, as compared to the native chitosan, CDP, especially low M_w derivatives (H _24h) exhibited potent antioxidant activities, while high M_w derivatives, especially C _24h, markedly inhibited the growth of all tested bacteria and fungi. These results may provide novel insights into the efficiency of chitosan depolymerisation using the Portunus segnis digestive crude chitosanase as a simple, inexpensive and easily method to produce bioactive chitosan-derivatives and that this bioactivity depends highly on their attractive characteristics.

Keywords: Biological activities; Chitosan-depolymerization products; Digestive chitosanase; Functional properties; Physicochemical characterization.