Abstract: In order to improve the enzyme quantity and activity from microbial strains, shorten fermentation time of enzyme production, this article aimed to study the optimization of fermentation process and preliminary catalytic conversion of β-D-glucuronidase from Bacillus subtilis, JY24 strain. Culture conditions for the production of β-D-glucuronidase from Bacillus subtilis JY24 strain were optimized by single factor method; the compositions of culture medium and conversion of baicalin were respectively studied by orthogonal design and HPLC. The result showed that the optimal culture conditions were: fermentation time, 42 h; rotational speed, 240 r/min; 50 mL culture in 500 mL liquid volume; initial culture medium, pH 7.0; temperature, 35 ℃； inoculation amount, 4％. The optimal compositions of medium were: sucrose, 8.0 g/L; yeast extract, 11.0 g/L; KH2PO4 , 0.38 g/L; K2HPO4 , 0.38 g/L; CaCl2 , 0.27 g/L; KNO3, 0.20 g/L; tween-20, 2.0 mL/L; corns steep, 1.0 mL/L; baicalin, 1.5 g/L. Under the optimized fermentation process, the enzyme activity of β-D-glucuronidase of Bacillus subtilis JY24 strain could reach 935.50 U/mL, which was 25.68 times higher than that before optimization, and the fermentation time for enzyme production was greatly shortened by 2.25-12.25 d. The preliminary results of catalytic conversion showed that the conversion rate of baicalin was 31.20%.

Key words: feed, Bacillus subtilis, β-D-glucuronidase, fermentation process, orthogonal design, bioconversion