Screening Of A Chitosan-hydrolytic Bacterium And Studies On Enzymatic Hydrolysates

A chitosanase-producing bacterium was isolated from soil samples and named as QY01. The strain QY01 was identified by 16SrDNA sequence, morphological, biochemical and physiological identification. The sequence data aligned with 16SrDNA sequences deposited in GenBank indicate that the strain QY01 belonged to the genus of Bacillus and the morphological, biochemical and physioogical characteristics also showed that the strain QY01 belonged to Bacillus sp.The optimum medium composition for producing chitosanase was as follows(%,w/v):colloid chitosan 1.0, glucose 0.1, yeast extract 0.5, K2HPO4.3H2O 0.2, MgSO4.7H2O 0.1, MgSO4·7H2O 0.1, NaCl 0.5, (NH4)2SO4 0.5, the initial pH 6.0. The optimal cultivation conditions for QY01 producing chitosanase were 6% (v/v) amount of inoculation, 30℃incubating temperature and shaking cultivation at 160 r/min for 72 hours. The maximal chitosanase activity could reach 10.87 U/ml when QY01 was incubated in flask under the oprimal cultural conditions.The optimal temperature and pH for hydorlysis of chitosan by the chitosanase were 45℃and 5.0, respectively; The chitosanase activity was stable in the pH range of 4.5～7.0 and the temperature under 55℃; Mg2+,Mn2+ enhanced the enzyme activity significantly,whereas Zn2+,Co2+,Fe3+ and Cu2+ inhibited the enzyme activity; The enzyme show activity for hydrolysis of chitosan and chitin, and 1% colloidal chitosan could be degraded most effectively.The main product of chitosan-hydrolysis was identified as polymerization of 2 ~ 6 shell oligosaccharides by FACE analysis.The present research showed that QY01 has a better value and prospect of development.