Optimization production of acid urease by Enterobacter sp. in an approach to reduce urea in Chinese rice wine.

Urea in alcoholic beverages is a precursor of ethyl carbamate, which is carcinogenic. Acid urease (EC 3.5.1.5) is regarded as a good approach to scavenge the urea. The acid urease of Enterobacter sp. R-SYB082, with lower optimum pH than the widely used commercial acid urease, exhibited a urea removal rate of 66.5% in Chinese rice wine, which was higher than that of the commercial acid urease (58.9%). The production of the acid urease was optimized from 1,100 to 2,504 U L(-1) by an approach which includes the optimization of initial glucose concentration, the elevation of anaerobic level of the reactor by charging CO(2) and in vitro natural activation of the target enzyme by simple cold storage (4°C). These would open up the possibility for developing industrial application of this acid urease for producing high-quality Chinese rice wine.