A thermostable chitosanase, purified 156-fold to homogeneity in an overall yield of 12.4%, has a molecular weight of about 29,000±2,000, and is composed of monomer. The enzyme degraded soluble chitosan, colloidal chitosan, and glycol chitosan, but did not degrade chitin or other β-linked polymers. The enzyme activity was increased about 2.5-fold by the addition of 10 mM Co²⁺ and 1.4-fold by Mn²⁺. However, Cu²⁺ ion strongly inhibited the enzyme. Optimum temperature and pH were 60°C and 6.5, respectively. The enzyme was stable after heat treatment at 80°C for 30 min or 70°C for 60 min and fairly stable in protein denaturants as well. Chitosan was hydrolyzed to (GlcN)₄ as a major product, by incubation with the purified enzyme. The effects of ammonium sulfate and organic solvents on the action pattern of the thermostable chitosanase were investigated. The amounts of (GlcN)₃-(GlcN)₆ were increased about 30% (w/w) in DAC 99 soluble chitosan containing 10% ammonium sulfate, and (GlcN)₁ was not produced. The monophasic reaction system consisted of DAC 72 soluble chitosan in 10% EtOH also showed no formation of (GlcN)₁, however, the yield of (GlcN)₃ ∼ (GlcN)₆ was lower than DAC 99 soluble chitosan-10% ammonium sulfate. The optimal concentration of ammonium sulfate to be added was 20%. At this concentration, the amount of hexamer was increased by over 12% compared to the water-salt free system.

This article cannot obtain the latest cited-by information.