Biochemical characterization and elucidation action mode of a new endolytic chitosanase for efficient preparation of chitosan oligosaccharides

Chitosan oligosaccharide (COS) is a high value-added derivative with intriguing uses in the food, pharmaceutical, and cosmetic industries. Herein, a new chitosanase (CscA) from Kitasatospora setae KM-6054 was cloned and heterologously expressed in Escherichia coli BL21(DE3). CscA showed the highest sequence identity (87.7%) with the chitosanase from Amycolatopsis sp. CsO-2 and was recognized as a new glycoside hydrolase (GH) family 46 chitosanase. The recombinant chitosanase CscA was purified by Ni-NTA Sepharose column and showed a relative molecular weight of 31.07 kDa. CscA had the highest activity (241.39 U/mg) at pH 5.0 and 60 °C. CscA had a wide pH tolerance range, maintaining more than 70% activity in the pH range of 3–10. Furthermore, the enzyme decomposed chitosan to generate chitobiose ((GlcN)₂), chitotriose ((GlcN)₃), chitotetraose ((GlcN)₄), and chitopentaose ((GlcN)₅) products. CscA was shown to be a potential chitosanase for the efficient manufacture of COSs from chitosan, which has several uses in food and industry.