Beauty in the Yeast

Saccharomyces cerevisiae is a tiny organism with a big job. It’s the emperor of fermentation, overseeing the production of beer, wine, cider, spirits, bread, and biofuels.

That’s quite a résumé for one single-celled species.

[caption caption="Chris Curtin, OSU’s brewing microbiologist, can tell the history of brewing from genomic clues he finds in yeast. By understanding how yeast has evolved, Curtin explores new strains to add variety to modern craft beers. (Photo by Stephen Ward.)"] [/caption]

Chris Curtin, OSU’s brewing microbiologist, explores the evolution of Saccharomyces cerevisiae—a challenge, as there’s no fossil record for single-cell yeasts. So, he examines the genome for clues. Research efforts from various labs suggest a significant point of diversity, at a time in the 17th century, when Saccharomyces cerevisiae began spinning off lots of varieties. Curtin says that’s when people began to differentiate fermented brews and to domesticate the varieties of scum that resulted in the best bread, wine, or beer.

Two varieties rose to the top for brewing beer: yeast for ale and yeast for lager. Today, there are more than 60 defined beer styles in the world, and all are sorted by these two varieties of Saccharomyces.

Like the other ingredients in beer, the action of yeast can generate a range of beer flavors as varied as apple, rose, or clove. What other flavors and aromas might be possible? Curtin is exploring the possibilities.

“I’m interested in how this species has evolved, its microbial ecology, and how we might develop novel yeast strains for brewers to expand their palette of flavors and aromas,” Curtin said.