The High-Throughput Screening of Microorganisms to Eliminate Ethyl Carbamate in Chinese Liquor

Ethyl carbamate (EC) is a 2A classified carcinogen in Chinese liquor that has raised many problems regarding food safety. Applying microorganisms to control the content of EC precursors in fermented grains has been proven as an effective method to reduce EC in alcoholic beverages. However, the utilization of microorganisms to decrease the precursors of EC (urea and cyanide) is still incomplete in regard to Chinese liquor. Thus, it is necessary to isolate strains with the degradative activities of urea and cyanide. Herein, Bacillus sonorensis F3 and Bacillus licheniformis YA2 strains were isolated from the fermented grains through multiple rounds of high-throughput screening, and the degradative abilities in urea and cyanide reached 95.72% and 75.48%, respectively. In addition, the urease from the B. sonorensis F3 strain and the carbon nitrogen hydrolase from the B. licheniformis YA2 strain were identified by the heterogeneous expression in Escherichia coli. Then, both F3 and YA2 strains were combined at a ratio of 5:1 and applied to eliminate the EC in the simulated fermentation of Chinese liquor; as a result, 51.10% of EC was reduced without affecting the main composition of flavor substances. The obtained strains have great potential in terms of the improvement of quality and safety of Chinese liquor.