title: Enhancement of ethanol fermentation in Saccharomyces cerevisiae sake yeast by disrupting mitophagy function.
abstract: Saccharomyces cerevisiae sake yeast strain Kyokai no. 7 has one of the highest fermentation rates among brewery yeasts used worldwide; therefore, it is assumed that it is not possible to enhance its fermentation rate. However, in this study, we found that fermentation by sake yeast can be enhanced by inhibiting mitophagy. We observed mitophagy in wild-type sake yeast during the brewing of Ginjo sake, but not when the mitophagy gene (ATG32) was disrupted. During sake brewing, the maximum rate of CO2 production and final ethanol concentration generated by the atg32Δ laboratory yeast mutant were 7.50% and 2.12% higher than those of the parent strain, respectively. This mutant exhibited an improved fermentation profile when cultured under limiting nutrient concentrations such as those used during Ginjo sake brewing as well as in minimal synthetic medium. The mutant produced ethanol at a concentration that was 2.76% higher than the parent strain, which has significant implications for industrial bioethanol production. The ethanol yield of the atg32Δ mutant was increased, and its biomass yield was decreased relative to the parent sake yeast strain, indicating that the atg32Δ mutant has acquired a high fermentation capability at the cost of decreasing biomass. Because natural biomass resources often lack sufficient nutrient levels for optimal fermentation, mitophagy may serve as an important target for improving the fermentative capacity of brewery yeasts.
authors.affiliation: Department of Environmental Science, Faculty of Agriculture, Saga University, Saga, Japan.
authors.forename: Shodai
authors.initials: S
authors.lastname: Shiroma
authors.forename: Lahiru Niroshan
authors.initials: LN
authors.lastname: Jayakody
authors.forename: Kenta
authors.initials: K
authors.lastname: Horie
authors.forename: Koji
authors.initials: K
authors.lastname: Okamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagaki
mesh_terms: D000071183:Autophagy-Related Proteins; D002245:Carbon Dioxide / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D055786:Gene Knockout Techniques; D063306:Mitophagy; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
chemical_list: C543183:Atg32 protein, S cerevisiae; D000071183:Autophagy-Related Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D002245:Carbon Dioxide; D000431:Ethanol