Purification, characterization, and action mode of a chitosanase from Streptomyces roseolus induced by chitin

Chitosanase (EC3.2.1.132) catalyzes the hydrolysis of beta-1,4-glycosidic bonds in chitosan, converting it into chitooligosaccharides, which exhibit versatile application potentials in food, pharmaceutical, and agricultural areas. In this paper we present a new inducible chitosanase, isolated, and purified from a bacterial culture medium of Streptomyces roseolus DH by precipitation with ammonium sulfate and combined column chromatographies. The SDS-PAGE results show its molecular mass is around 41 kDa, with a purity of more than 95%. The purified chitosanase exhibits optimum activity at 50 degrees C, pH 5.0. It is stable between 30 and 60 degrees C and at pH values between 5 and 7. It shows the highest activity towards colloidal chitosan and breaks down glycol chitosan and glycol chitin weakly. The enzyme is significantly inhibited by Cu2+, Co2+, Mn2+, Zn2+, and EDTA, but slightly activated by Mg2+. Further action mode analysis based on chitosan oligomers and a polymer reveals that the chitosanase could split chitooligosaccharides with degree of polymerization (DP) > 4 and chitosan in an endolytic manner. The resultant hydrolytes are mainly chitotrisaccharides, indicating it is suitable for the uniform bioconversion of chitosan and its derivatives with high efficiency. (C) 2012 Elsevier Ltd. All rights reserved.