Presentation Information
[3SBT-13-KL]Genetic analysis of high malic acid-producing sake yeasts and its applications
○Hiroaki Negoro1 (1. Research Institute, Gekkeikan Sake Co. Ltd. (Japan))
Keywords:
Japanese sake,Saccharomyces cerevisiae;,Malic acid,VID24,PEX22
[Purpose]
The budding yeast Saccharomyces cerevisiae is widely used in the production of alcoholic beverages, including wine, beer, and sake, a traditional Japanese alcoholic beverage. During fermentation, yeast produces not only ethanol but also esters, amino acids, and organic acids. Major organic acids in sake include succinic acid, malic acid, and lactic acid. Since malic acid contributes to the desirable sour taste of sake, various non-genetically modified breeding methods have been developed to obtain high malic acid-producing strains. However, the genetic basis underlying the phenotype remains unclear. This study aimed to identify the gene mutations responsible for elevated malic acid production and to elucidate the underlying mechanisms.
[Methods]
High malic acid-producing strains were isolated from sake yeasts based on their sensitivity to dimethyl succinate. Whole-genome comparative analyses were conducted to identify mutations responsible for the phenotype.
[Results and consideration]
Two high malic acid-producing strains, K-901H and F-701H, were obtained from K-901 and F-701, respectively.
Genome sequencing revealed that a missense mutation in the VID24 gene was responsible for the high malic acid phenotype in K-901H. Vid24 is a component of the glucose-induced degradation (GID) complex, which promotes the degradation of gluconeogenic enzymes such as fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and cytosolic malate dehydrogenase (Mdh2). In the VID24 mutant, impaired degradation led to the accumulation of Mdh2 in the cytoplasm, enhancing the reduction of oxaloacetate to malate.
In F-701H, genome analysis identified a nonsense mutation in PEX22, a gene encoding a peroxin involved in peroxisomal homeostasis. Pex22 plays a critical role in the import of peroxisomal matrix proteins. Dysfunction of Pex22 disrupted the localization of peroxisomal malate dehydrogenase (Mdh3), resulting in its mislocalization and increased malic acid production in the cytoplasm.
[Conclusion]
These findings provide new insights into the genetic and metabolic mechanisms regulating malic acid production in yeast. The isolated strains have practical applications in sake brewing, where modulation of malic acid levels can contribute to improved product quality.
The budding yeast Saccharomyces cerevisiae is widely used in the production of alcoholic beverages, including wine, beer, and sake, a traditional Japanese alcoholic beverage. During fermentation, yeast produces not only ethanol but also esters, amino acids, and organic acids. Major organic acids in sake include succinic acid, malic acid, and lactic acid. Since malic acid contributes to the desirable sour taste of sake, various non-genetically modified breeding methods have been developed to obtain high malic acid-producing strains. However, the genetic basis underlying the phenotype remains unclear. This study aimed to identify the gene mutations responsible for elevated malic acid production and to elucidate the underlying mechanisms.
[Methods]
High malic acid-producing strains were isolated from sake yeasts based on their sensitivity to dimethyl succinate. Whole-genome comparative analyses were conducted to identify mutations responsible for the phenotype.
[Results and consideration]
Two high malic acid-producing strains, K-901H and F-701H, were obtained from K-901 and F-701, respectively.
Genome sequencing revealed that a missense mutation in the VID24 gene was responsible for the high malic acid phenotype in K-901H. Vid24 is a component of the glucose-induced degradation (GID) complex, which promotes the degradation of gluconeogenic enzymes such as fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and cytosolic malate dehydrogenase (Mdh2). In the VID24 mutant, impaired degradation led to the accumulation of Mdh2 in the cytoplasm, enhancing the reduction of oxaloacetate to malate.
In F-701H, genome analysis identified a nonsense mutation in PEX22, a gene encoding a peroxin involved in peroxisomal homeostasis. Pex22 plays a critical role in the import of peroxisomal matrix proteins. Dysfunction of Pex22 disrupted the localization of peroxisomal malate dehydrogenase (Mdh3), resulting in its mislocalization and increased malic acid production in the cytoplasm.
[Conclusion]
These findings provide new insights into the genetic and metabolic mechanisms regulating malic acid production in yeast. The isolated strains have practical applications in sake brewing, where modulation of malic acid levels can contribute to improved product quality.
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