Purification and properties of chitosanase from a mutant of Bacillus subtilis IMR-NK1

Chitosanase was purified from the crude enzyme preparation of Bacillus subtilis IMR-NK1. The purified chitosanase had an optimal pH of 4.0, an optimal temperature of 45 °C for chitosan hydrolysis. The molecular mass estimated by gel filtration was 36 kDa. Chemical modification agents N-bromosuccinimide (0.05 mM) and p-hydroxymercuribenzoic acid (0.5 mM), and heavy metal ion of Hg2+ (0.1 mM) significantly or completely inhibited the activity of the enzyme. The enzyme also showed activity for hydrolysis of glycol chitosan and colloidal chitin. In the hydrolysis of chitosans of varying N-acetyl content, the enzyme degraded 60–94% deacetylated chitosan most effectively. End products of chitosan hydrolysis by the enzyme were chitobiose to chitotetraose and some chitooligosaccharides with a longer chain length. For chitooligosaccharides hydrolysis, the smallest of the substrates was a glucosamine tetramer.