title: Construction and evaluation of self-cloning bottom-fermenting yeast with high SSU1 expression.
abstract: OBJECTIVE
  To construct a self-cloning brewer's yeast that can minimize the unfavourable flavours caused by oxidation and certain kinds of sulfur compounds.
  
  
  RESULTS
  DNA fragments of a high-expression promoter from the TDH3 gene originating from Saccharomyces cerevisiae were integrated into the promoter regions of the S. cerevisiae-type and Saccharomyces bayanus-type SSU1 genes of bottom-fermenting brewer's yeast. PCR and sequencing confirmed the TDH3 promoter was correctly introduced into the SSU1 regions of the constructed yeasts, and no foreign DNA sequences were found. Using the constructed yeasts, the concentration of sulfite in fermenting wort was higher when compared with the parent strain. In addition, the concentrations of hydrogen sulfide, 3-methyl-2-buten-1-thiol (MBT) and 2-mercapto-3-methyl-1-butanol (2M3MB) were lower when compared with the parent strain.
  
  
  CONCLUSIONS
  We successfully constructed a self-cloning brewer's yeast with high SSU1 expression that enhanced the sulfite-excreting ability and diminished the production ability of hydrogen sulfide, MBT and 2M3MB.
  
  
  CONCLUSIONS
  The self-cloning brewer's yeast with high SSU1 expression would contribute to the production of superior quality beer with a high concentration of sulfite and low concentrations of hydrogen sulfide, MBT and 2M3MB.
authors.affiliation: Research Laboratory of Brewing Technology, Asahi Breweries Ltd, Ibaraki, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Iijima
authors.forename: T
authors.initials: T
authors.lastname: Ogata
mesh_terms: D020001:1-Butanol / Q000032:analysis; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D001515:Beer / Q000382:microbiology; D002073:Butanes / Q000032:analysis; D004271:DNA, Fungal / Q000032:analysis / Q000235:genetics; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D005818:Genetic Engineering / Q000379:methods; D006862:Hydrogen Sulfide / Q000032:analysis; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000032:analysis; D013447:Sulfites / Q000032:analysis* / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D002073:Butanes; D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; C108311:Ssu1 protein, S cerevisiae; D013438:Sulfhydryl Compounds; D013447:Sulfites; D020001:1-Butanol; C512562:3-methyl-2-butene-1-thiol; D006862:Hydrogen Sulfide