Constitutive expression of DUR1, 2 gene in Chinese rice wine yeast

Ethyl carbamate (EC) is a potential carcinogen for human, which can be found in many fermented alcoholic beverages.The main precursor for EC is urea produced by yeast.The DUR1, 2 gene which encoded urea amidolyase was cloned into plasmid pYX212 between the TPI promoter and terminator sites to form the DUR1, 2 expression cassette.The cassette was then integrated into the genome of the Chinese rice wine yeast 85.Thus a urea-degrading Chinese rice wine yeast 85 DUR1, 2 was obtained.According to the laboratory scale rice wine brewing tests, urea was reduced to 8.34mg/L by yeast 85DUR1, 2, 69.9%less than the parental strain, while the ethyl carbamate level was 40.5%less than that of the parental strain after a period of storage.Meanwhile, 85DUR1, 2 was substantially equivalent to its parental strain in terms of fermentation ability, ethanol, total acid and amino nitrogen.