Japanese sake lovers now have more reason to love the Japanese alcoholic beverage. Scientists have found a new yeast strain that produces high levels of amino acid ornithine known to have the ability to fight fatigue.
Ornithine is known for its fatigue-fighting properties, as well as improving athletic performance. But ornithine is also used for wound healing, weight loss, and improving sleep quality. The one found in the study, a non-genetically modified mutant strain, can be easily applied in brewing the sake.
Mutant Sake Yeast Strain Produces High Levels of Ornithine
Researchers from the Nara Prefecture Institue of Industrial Development and Nara Institute of Science and Technology have discovered a mutant strain of sake yeast that produces ten times the amount of the amino acid ornithine than its parent yeast strain.
As a non-protein-making amino acid and a precursor to arginine and proline, ornithine performs several physiological functions like improving sleep quality and fighting fatigue.
Masataka Ohashi, the first author of the study, said that they wanted to get sake yeast strains with improved ethanol tolerance. The yeast is exposed to high concentrations of ethanol during the fermentation process, obstructing the viability, cell growth, and fermentation.
Improved ethanol production and lesser fermentation time are achieved when ethanol tolerance in sake yeast is increased.
The researchers sequestered mutant yeast strains that have collected proline to look for yeast strains that are ethanol-tolerant, which can lessen ethanol toxicity using conventional mutagenesis, like one that does not include genetic modification.
Moreover, the researchers also performed brewing tests using sake yeast strains and conducted genome sequence analysis. After that, they identified and examined a new yeast strain from a gene of the yeast that encodes a variant of N-acetyl glutamate kinase, which increases the level of ornithine in cells.
Corresponding author Professor Hiroshi Takagi said they initially constructed industrial yeast strains that can clone itself and that accumulate proline to increase the productivity and ethanol tolerance of the yeast.
However, even if self-cloning yeasts do not contain any foreign genes or DNA sequences because they only have yeast DNA, those yeasts are deemed not acceptable to the public as they are considered to be genetically modified.
The researchers successfully isolated non-genetically modified yeasts that have high levels of the ornithine, about ten times of the parent yeast widely used in the Japanese sake.
Purpose of the Mutated Yeast Strain
The researchers hope that the results of their study would be used in developing new strains of yeasts for the production of high levels of ornithine. Plus, the yeast strain they discovered in this study could be used in the production of dietary supplements rich in ornithine that are made from yeasts.
Moreover, Professor Takagi explains that there are two purposes for breeding industrial yeast. First, it is for the enhancement of its fermentation ability and a boosted tolerance to environmental stresses during fermentation, and the diversity of the flavors of the product.
The development of yeast strains that overproduce functional amino acids would contribute so much in food-related industries.
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