Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast

Abstract

The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast () leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their "petite" strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile. Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of increased mitochondrial activity. This novel discovery will enable the selection of favorable brewery yeasts by monitoring the copy numbers of specific chromosomes through a process that does not involve generation/use of genetically modified organisms.

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“…Zhu, Sherlock and Petrov 2016;Peter et al 2018). These phenomena can alter their industrial performance and may happen very rapidly (Zhang et al 2016;Kadowaki et al 2017;Morard et al 2019;Gorter de Vries et al 2020;Large et al 2020). Along with point mutations, these GSV events result in clonal populations gradually accumulating differences in various traits, leading to clonal heterogeneity, clonal interference (competition among isogenic asexual lineages) and hence the emergence of so-called subclonal lineages, reminiscent of the experimental evolution setups conducted with laboratory strains (e.g.…”

Glycosylceramide modifies the flavor and metabolic characteristics of sake yeast

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