Optimization of the Fermentation Conditions for Producing Urethanase by Lysinibacillus fusiformis

Abstract:

Ethyl carbamate （EC） is a potential carcinogen which widely exists in alcohol beverage and fermented food. Enzyme degradation is one of the important routes to deal with the EC contamination. In this study，a bacteria Lysinibacillus fusiformis SC02 which was able to degrade EC was isolated from mice stomach as the starting strain. The condition of enzyme production was optimized by using single-factor test. The optimal fermentation medium components were as follows：galactose 25 g/L，soy peptone 20 g/L，urea 4 g/L，CuSO4 0.02 g/L，initial pH 6.0. The optimal conditions for enzyme-producing were as below：temperature 37 ℃，inoculum volume 3% and liquid volume in flask 20 mL/250 mL. Urethanase production level of the strain was improved from 900 U/L to 4 500 U/L after being cultured for 15 h under the conditions mentioned above，which was 350% higher than the one under the original conditions. After investigating the influences of different agitation speeds on the urethanase production at the fermentation tank level，800 r/min was chosen as the optimal agitation speed，and the urethanase activity can reach to 7066 U/L at this speed，which was 57% higher than before.