Fermentation Conditions of Chitinase Producing by the Endophytic Bacterium Bacillus thuringiensis Bt028 Isolated from Sour Orange

In order to improve the chitinase production performance of an endophytic bacterium Bacillus thuringiensis Bt028 isolated from sour orange fruit, the effects of medium composition and fermentation conditions on chitinase production were investigated by single factor test and the shaking flask fermentation conditions of chitinase production were optimized by response surface methodology. The results of single factor test showed that concentration of colloidal chitin, temperature and initial pH had obvious effects on chitinase production. The results of response surface test showed that the optimum fermentation conditions were as follows: Colloidal chitin concentration was 0.8%, yeast powder concentration was 1%, the initial pH was 6.9, inoculation amount was 3%, liquid volume was 100 mL/250 mL, cultured temperature was 30 ℃ and culture time was 48 h. Under these conditions, the highest enzyme activity of the strain fermentation broth was 10.48 U/mL. The studied results laid a foundation for the further development and application of the chitinase produced by Bacillus thuringiensis Bt028.