Construction of the recombinant yeast strain with transformation of rice starch-saccharification enzymes and its alcohol fermentation

Department of Cosmetology, Dongkang College, Gwangju 61200, Republic of Korea(Received April 4, 2016; Revised May 9, 2016; Accepted May 10, 2016)ABSTRACT: To improve antioxidant glutathione (GSH) content and saccharification ability in sake yeasts of Saccharomyces cerevisiae, the γ-glutamylcysteine synthetase gene (GSH1 ) from S. cerevisiae, glucoamylase gene (GAM1 ) and α-amylase gene (AMY ) from Debaryomyces occidentalis were co-expressed in sake yeasts for manufacturing a refreshing alcoholic beverage abundant in GSH from rice starch. The extracellular GSH content of the recombinant sake yeasts increased 1.5-fold relative to the parental wide-type strain. The saccharification ability by glucoamylase of the new yeast strain expressing both GAM1 and AMY genes was 2-fold higher than that of the yeast strain expressing only GAM1 gene when grown in the culture medium containing 2% (w/v) rice starch. It generated 11% (v/v) ethanol from 20% (w/v) rice starch and consumed up to 90% of the starch content after 7 days of fermentation.Key words: Saccharomyces cerevisiae, fermentation, glutathione, rice starch, saccharification*For correspondence.