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The selection of yeast with good fermentation characteristics is critical for producing beer with desirable qualities. A yeast population was selected with an enhanced fermentation rate, referred to as high‐fermentation yeast (HFY), which was derived from the wild‐type Sacchromyces pastorianusyeast population (WTY). To identify genes that contribute to the fermentation performance, we compared the genetic profiles of the WTY and HFY populations by next‐generation sequencing. Several chromosomal regions were found to exhibit markedly different sequence coverage, suggesting chromosomal duplications and deletions, which might have occurred during selection of the HFY population. Among the genes with altered coverage, the copy number of the Saccharomyces eubayanus‐type YCK1(SeYCK1) gene was almost two times higher in the HFY population than in the WTY population. The gene which is involved in glucose sensing in Saccharomyces cerevisiaewas at a higher level in the HFY population throughout fermentation. These findings suggest that the chromosomal duplication of a region including the SeYCK1gene locus of the HFY population is at least partially responsible for the differences in the fermentation properties between the WTY and HFY populations. © 2018 The Institute of Brewing & Distilling

A polymerase chain reaction (PCR) method for the detection of Pectinatus cerevisiiphilusand P. frisingensiswas developed. The 16S rRNA gene (rDNA) and the spacer regions between the 16S rDNA and the 23S rDNA genes were used for the PCR reaction. The species-specific sequences in the spacer region between the 16S rDNA and the 23S rDNA genes were selected for use as PCR primers. The method developed in this study was rapid and sensitive. Furthermore, this method allowed identification at the species level, even between very closely related species, such as P. cerevisiiphilusand P. frisingensis.

A total of 39 Pectinatusstrains have been ribotyped in this investigation. Thirteen different ribotypes were observed from 34 strains of P. frisingensis, while three different types were shown with five strains of P. cerevisiiphiluswhen digested with EcoRI. These patterns consisted of two series of fragments: fragments conserved within a species, and polymorphic variation. P. frisingensishad conserved fragments of ≈2.5– 3, 7–8, and 10–20 kbp, whereas P. cerevisiiphilushad ≈2–3, 5–6, and 20– 30 kbp. These fragment patterns, characterized by sets of conserved fragments within a species, were species specific. Furthermore, the HindIII-and BamHI-digested restriction patterns have been examined to facilitate differentiation at the strain level. Thirty-four strains of P. frisingensiscould be divided into 1 of 12 types. On the other hand, a composite ribotype, which combined the ribotypes produced by all restriction enzymes used, produced such high definition that all strains of P. frisingensisfell into 1 of 17 types.