High-level expression and characterization of recombinant acid urease for enzymatic degradation of urea in rice wine.

Ethylcarbamate, a carcinogenic compound, is formed from urea and ethanol in rice wine, and enzymatic elimination of urea is always attractive. In the present work, we amplified the acid urease gene cluster ureABCEFGD from Lactobacillus reuteri CICC6124 and constructed robust Lactococcus lactis cell factories for the production of acid urease. The titer of the recombinant acid urease was increased from 1,550 to 11,560 U/L by optimization of the cultivation process. Meanwhile, the enzyme showed satisfied properties toward urea elimination in the rice wine model system. By incubating the enzyme (50 U/L) at 20 °C for 60 h, about 95.8% of urea in rice wine was removed. Interestingly, this acid urease also exhibited activity toward ethylcarbamate. The results demonstrated that this recombinant acid urease has great potential in the elimination of urea in rice wine.