Expression and Molecular Modification of Chitin Deacetylase from Streptomyces bacillaris .

Chitin deacetylase can be used in the green and efficient preparation of chitosan from chitin. Herein, a novel chitin deacetylase Sb CDA from Streptomyces bacillaris was heterologously expressed and comprehensively characterized. Sb DNA exhibits its highest deacetylation activity at 35 °C and pH 8.0. The enzyme activity is enhanced by Mn 2+ and prominently inhibited by Zn 2+ , SDS, and EDTA. Sb CDA showed better deacetylation activity on colloidal chitin, (GlcNAc) 5 , and (GlcNAc) 6 than other forms of the substrate. Molecular modification of Sb CDA was conducted based on sequence alignment and homology modeling. A mutant Sb CDA63G with higher activity and better temperature stability was obtained. The deacetylation activity of Sb CDA63G was increased by 133% compared with the original enzyme, and the optimal reaction temperature increased from 35 to 40 °C. The half-life of Sb CDA63G at 40 °C is 15 h, which was 5 h longer than that of the original enzyme. The improved characteristics of the chitin deacetylase Sb CDA63G make it a potential candidate to industrially produce chitosan from chitin.