S-2. Research of brewer's yeast based on genome information
Tomoo Ogata, Asahi Breweries, Ltd., Moriya, Japan
ABSTRACT: Brewer's yeast has unique characteristics different from other yeasts, such as high wort fermentation ability and flocculation. We investigated these characteristics of brewer's yeast by genome analysis, which has rapidly advanced in recent years, to contribute to the construction of more adequate yeast strains. Bottom-fermenting yeast, Saccharomyces pastorianus, is a natural hybrid between S. cerevisiae (SC) and S. bayanus (SB). Therefore, it is different from S. cerevisiae, which laboratory yeast strains and top-fermenting yeast belong to. This fact has been confirmed by Southern hybridization and other experiments (Yamagishi and Ogata, System. Appl. Microbiol. 22:341-353, 1999). Bottom-fermenting yeast has both SC- and SB-types of genes and chromosomes. But, our genome analysis revealed that bottom-fermenting yeast has some characteristic chromosomes, and some of these chromosomes have SC and SB sequences crossing each other (Ogata et al, J. Applied Microbiol. 107:1098-1107, 2009). One of the characteristic chromosome structures of bottom-fermenting yeast is SC-type chromosome VIII. The Lg-FLO1 gene, which encodes the specific agglutinin, is located on the right arm end of SC-type chromosome VIII. In the case of the laboratory yeast S. cerevisiae S288C, FLO5 is located on this region. In most bottom-fermenting yeast strains, this region is heterozygous. In the case that LOH (loss of heterozygosity) occurs and Lg-FLO1 is missing, these yeast strains lose flocculation ability (Ogata et al, J. Applied Microbiol. 105:1186-1198, 2008). We constructed new yeast strains using the genome information of bottom-fermenting yeast. Bottom-fermenting yeast has both an SC- and SB-type SSU1 gene that encodes for the sulfite efflux pump. We successfully constructed a brewer's yeast with high SSU1 expression that enhanced the sulfite-excreting ability and diminished the production ability of hydrogen sulfide, MBT, and 2M3MB. This new brewer's yeast strain would contribute to the production of superior quality beer (Iijima and Ogata, J. Applied Microbiol. 109:1906-1913, 2010).
Tomoo Ogata received an M.S. degree in pharmacology science from Chiba University. After graduation in 1985, he worked on brewing microbiology at the Research Laboratories for Brewing, Asahi Breweries, Ltd. He received a Ph.D. degree in microbiology science from the University of Tokyo in 1997 and an award from the Brewing Society of Japan in 2001.