Ikoma, Japan—As consumer interest grows in foods and beverages with added nutritional value, brewers are exploring ways to improve fermentation itself rather than relying on post-production additives. Ornithine, a naturally occurring amino acid involved in several biological processes, has attracted attention as a promising ingredient for value-added products. However, increasing ornithine production in brewing yeast is difficult because the metabolic pathway is tightly regulated, making conventional improvement strategies challenging.
Addressing this challenge, Professor Hiroshi Takagi and his research team (Associate Professor Akira Nishimura, Assistant Professor Shota Isogai, and Dr. Ryoya Tanahashi) of the Laboratory of Fermentation Science at Nara Institute of Science and Technology, Japan, combined traditional microbial breeding with modern molecular analysis to develop a practical, non-genetically modified brewing yeast. Their findings were published in the Journal of Industrial Microbiology and Biotechnology on May 20, 2026. More information about the Laboratory of Fermentation Science is available at https://www.naist.jp/iri/takagi/ .
The project began with a wild Saccharomyces cerevisiae strain isolated from a university campus, highlighting the continuing value of local microbial resources. Instead of using gene editing, the team applied chemical mutagenesis followed by selection with canavanine, a toxic arginine analog. This traditional breeding-compatible strategy produced hundreds of candidate strains, from which one mutant, ADHorn49, showed more than nine times higher intracellular ornithine levels than the original yeast.
Whole-genome sequencing revealed that the enhanced trait could be traced to a single genetic change. The researchers identified a Gly351Asp substitution in the ARG6 gene, which encodes a key enzyme in ornithine biosynthesis. Additional experiments showed that introducing this mutation into different industrial yeast backgrounds consistently increased ornithine accumulation. Structural modeling further suggested that the mutation may alter interactions within the enzyme and reduce the strength of normal metabolic regulation.
"Valuable microorganisms can still be discovered from local natural environments," says Assoc. Prof. Nishimura (currently Professor at Iwate University), emphasizing that the work connects biodiversity exploration with modern fermentation science. He added that exploring wild yeast resources can create new opportunities for scientifically validated fermentation innovation.
Importantly, the improved yeast retained normal brewing performance. Fermentation tests showed that carbon dioxide production was comparable to that of the parental strain, while the mutant secreted significantly more ornithine into the brewing medium. The final fermentation broth contained 7.0 mg/L of free ornithine, demonstrating that the trait can be expressed under practical brewing conditions without compromising industrial usability.
"This study clearly demonstrates a practical non-genetically modified strategy that combines traditional microbial breeding with molecular understanding," says Prof. Takagi. "By linking natural-environment yeast resources with modern fermentation biotechnology, we hope to support the development of value-added fermented foods and beverages."
Overall, the study bridges traditional fermentation culture and cutting-edge biotechnology by combining wild yeast exploration, whole-genome sequencing, structural modeling, and nongenetically modified (non-GM) breeding. Beyond the possibility of producing ornithine-enriched craft beer, the approach could support the development of other value-added fermented foods and beverages while strengthening the role of microbial breeding in sustainable food innovation.
