Identification and expression of bifunctional acid urea-degrading enzyme/urethanase from Enterobacter sp. R-SYB082 and its application in degradation of ethyl carbamate in Chinese rice wine (Huangjiu)

Abstract

Background: Ethyl carbamate (EC) is a potential carcinogen existing in fermented foods such as Chinese rice wine (Huangjiu). Since urea is an important precursor of EC, the degradation of urea could be an effective way to reduce EC in foods.

Results: In this study, an Enterobacter sp. R-SYB082 with acid urea degradation characteristics was obtained through microbial screening. Further research isolated a new acid urea-degrading enzyme from R-SYB082 strain - ureidoglycolate amidohydrolase (UAH) - which could degrade EC directly. The cloning and expression of UAH in Escherichia coli BL21 (DE3) suggested that the activity of urea-degrading enzyme reached 3560 U L^-1 , while urethanase activity reached 2883 U L^-1 in the optimal fermentation condition. The enzyme had the dual ability of degrading substrate urea and product EC. The removal rate of EC in Chinese rice wine could reach 90.7%.

Conclusion: This study provided a new method for the integrated control of EC in Chinese rice wine and other fermented foods. © 2022 Society of Chemical Industry.

Keywords: Chinese rice wine; Enterobacteria; degradation; enzyme identification; ethyl carbamate; fermented foods.