Biochemical properties of a novel chitosanase from Bacillus amyloliquefaciens and its use in membrane reactor

Chitooligosaccharides are widely used in functional food, medicaments and agriculture. Controllable conversion of chitosan to chitooligosaccharides with desired degree of polymerization (DP) is of great value. Herein, a novel glycoside hydrolase family 46 chitosanase (BaCsn46A) was cloned and expressed from Bacillus amyloliquefaciens. BaCsn46A exhibited good enzymatic properties with high specific activity (1031.2 U/mg) under optimal hydrolysis conditions of pH 6.0 and 50 °C. BaCsn46A is an endo-type chitosanase, which could be utilized to yield abundant chitooligosaccharides. Furthermore, the preparation of high degree of polymerization chitooligosaccharides (DP 5–10) was investigated by BaCsn46A in an enzymatic reactor with a subsequent series of membranes. The maximum concentration of total chitooligosaccharides (DP 2–10) was 28.11 g/L (93.70% yield). The proportion of high degree of polymerization chitooligosaccharides (DP 5–10) occupied 56.17% (w/w) of total chitooligosaccharides. This study provided a cleaner production process for the controllable preparation of chitooligosaccharides with specific degree of polymerization.