The overexpression ofDUR1,2and deletion ofCAR1in an industrialSaccharomyces cerevisiaestrain and effects on nitrogen catabolite repression in Chinese rice wine production

Abstract

Urea is acknowledged as the predominant precursor of ethyl carbamate (EC) in Chinese rice wine. During Chinese rice wine fermentation, urea accumulates owing to the nitrogen catabolite repression effect when preferred nitrogen sources are available. In previous research, two metabolically engineered strains were constructed with overexpression of DUR1,2 and deletion of CAR1 from an industrial Chinese rice wine yeast N85. The decreasing effect of urea and EC was demonstrated during small-scale Chinese rice wine fermentations. The present study compared the urea utilization rate of the parental and metabolically engineered yeast strains, using a preferred and non-preferred nitrogen source culture media, leading to alleviated urea accumulation and thus EC formation. The qRT-PCR results showed that, in all of the culture media, DUR1,2 was overexpressed with the inserted strong promoter PGK1p. During pilot scale fermentations, the urea and EC content decreased with the engineered strains. These results confirmed that the engineered strains could resist the nitrogen catabolite repression effect. Copyright © 2016 The Institute of Brewing & Distilling