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

Chitosanase (EC3.2.1.132) catalyzes the hydrolysis of β-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 °C, pH 5.0. It is stable between 30 and 60 °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.

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► An extracellular chitosanase is co-induced by chitin in Streptomyces roseolus DH.
► A 41-kDa chitosanase was purified and characterized.
► The analysis of action mode by TLC suggests an endo-cleavage manner in degradation.
► The enzymatic hydrolysates towards oligomers and a polymer are mainly chitotrioses.