Recombinant expression of chitosanase from Bacillus subtilis HD145 in Pichia pastoris

A chitosanase-producing bacterium, Bacillus subtilis HD145 CCTCC AB 2010353, was isolated from a soil sample. The gene (csn) encoding chitosanase was cloned, sequenced, and expressed in the Pichia pastoris strain as a soluble and active form. Its expression level could be as high as 800 mg/L, and enzymatic activity reached approximately 9000 U/mg. The optimum pH and temperature were 5.5 and 50 °C, respectively. The recombinant protein was partially glycosylated. Its half lives at temperatures of 50 and 60 °C were 26 h and 23 min, respectively. Enzymatic activity was increased with an increasing degree of deacetylation of chitosan. The enzymatic productions of chitooligosaccharides from chitosans of various deacetylation degrees mainly ranged from chitobiose to chitopentamer.