Mulling the Microbe

Saccharomyces cerevisiae, a wine yeast, may become the first state microbe in Oregon

Say hello to a winemaker’s little friend. For thousands of years, yeast has graced us with its ability to turn grape juice into wine. Wine lovers owe a debt of gratitude to one species in particular, known to professionals as Saccharomyces cerevisiae. Variations of this species are used in brewing beer and in winemaking, reason enough to show some love for these helpful microbes.

Oregon might be the first state to demonstrate its appreciation for the little guys. On April 11, the Oregon House voted unanimously to pass House Concurrent Resolution 12, which designates S. cerevisiae, or brewer’s yeast, as Oregon’s official state microbe. If it passes the Senate, Oregon will be the first state to have an official microbe. It’s a big feat for a small species that helps bring billions of dollars to Oregon’s economy from the wine industry alone.

Although the relationship between winemakers and yeast spans more than 7,000 years, scientists didn’t know how yeast worked until around 150 years ago, when Louis Pasteur realized the role of yeast in alcohol production. As it turns out, winemaking started as a happy accident.

“The domestication of yeast was an unknown process to the ancient winemakers,” says Alan Bakalinsky, an associate professor in Food Science and Technology at Oregon State University. “They didn’t know yeast was required for making wine, but they knew that when these grapes were harvested and broken open, this transformation would occur.”

Since then, we’ve learned that yeast cells live on the surface of grapes, and when the cells are exposed to the sugary grape juice inside, they begin to feed off the sugar, excreting alcohol and carbon dioxide into the juice in a process called fermentation. Bakalinsky says that some modern wineries still rely on the natural microbial diversity present in their vineyards, while others buy yeast from commercial manufacturers.

Winemakers rely heavily on S. cerevisiae in particular, partly because it can outlast the other kinds of yeast present during the fermentation process. With its high tolerance for alcohol and sulfites in the wine, it lives on while the other species of yeast die from the high alcohol exposure. Early winemakers unwittingly domesticated S. cerevisiae by using it over and over again, encouraged by repeated success.

“We’ve selected strains that don’t produce a lot of stinky flavors and aromas,” Bakalinsky says. “Over time, winemakers have stuck with the yeasts that produce wonderful wines.”

And S. cerevisiae also produces great research — it was the first fungus to have its genome sequenced, and it is used as a model organism to study aging and genetics.

Bakalinsky says his “love affair” with S. cerevisiae began in the mid-’80s, and he is delighted to see the species getting a mention in the Oregon House. “I think it’s wonderful, especially in recognition of the outstanding wines we’re making here in Oregon and the growing excitement of the brewing community as well,” Bakalinsky says.

So next time you sip a glass of wine, make sure to toast the microbe that made it all possible.

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