Tracing the Genetic Lineage of Beer

The explosion of craft breweries in the last several years has opened up a world of possibilities for the discerning beer drinker, and for the brewers trying to satisfy their thirst. For many of these smaller breweries, like Three Heads Brewing in Rochester’s Neighborhood of the Arts, the ability to experiment is part of what sets them apart from larger operations. That doesn’t mean creating a consistent brand isn’t important.

“Consistency is your brand building. That's how you make your bread and butter,” says Bruce Lish, Director of Brewing Operations at Three Heads. “Your bread and butter also allows you to go out and try new things and experiment and that really drives people in the door to come try out what you've got coming up next.”

That drive to experiment, but also predict how the beer chemistry will turn out is part of what makes understanding the science of the brewing process so important.

Justin Fay, an associate professor of biology at the University of Rochester, studies yeast in order to tackle bigger questions about evolutionary biology. For example: What is the genetic basis of evolutionary change? What is the basis of differences among species or among individuals within a species?

“Whether that’s differences in temperature preferences or differences in certain domesticated brewing characteristics, we want to know what genes are involved,” Fay says.

In a paper published in the journal PloS Biology, Fay and his colleagues report some intriguing findings about a specialized strain of commercial yeast called Saccharomyces cerevisiae, also known as brewer’s yeast. S. cerevisiae has been used to make beer for thousands of years and is genetically distinct from wild populations of yeast. But while brewer's yeast has specialized characteristics, its historical origins have been difficult to determine because yeast was around long before people discovered microorganisms.

Fay and his colleagues set out to unravel the complex pedigree of brewer’s yeast by analyzing its genome. What they found was surprising: the genome of brewer’s yeast is actually derived from a combination of the yeast strains used to make European grape wine and the yeasts used to make Asian rice wine. The results provide information about the domestication of organisms and may offer brewers insights that can lead to novel, new beer flavors.

Beer is made from three essential ingredients: water, yeast, and a carbohydrate such as barley. Brewer’s yeast is known for its strong fermentative characteristics that, in the presence of oxygen, allow it to convert sugars from the carbohydrate into alcohol. It has gained the ability, much like grapes, to competitively dominate other species in high-sugar, low-nutrient environments.

Most beers, especially Western beers, are one of two types—ales or lagers. Cell division within the yeast—and the temperature—are essential in determining the beer’s flavor.


To reconstruct the history of modern ale strains, Fay and his colleagues sequenced and compared the genomes of modern brewer’s yeast to a panel of reference strains. That’s how they discovered that the genomes of the modern beer strains were similar to the genomes of European grape wine strains and Asian rice wine strains. The researchers conjecture that modern brewer’s yeast is derived from a melting pot of fermentation technology, resulting from an East-West transfer similar to the spread of domesticated plants and animals by way of the Silk Route, thousands of years ago.

While yeast has traveled the world, brewers have used different strains of S. cerevisiae in their beers. Fay’s research may open doors for even more unique brews.

“Beermakers are experimental, always wanting to try new things and make their beers distinct,” he says. “Very recently—and our study will add to this—beermakers have been exploring using other yeast strains besides the typical commercial beer strains. If you really want to be creative and do something different, you could go out and use a wild strain of yeast, but you need to be able to combine the beneficial characteristics of the yeast strains that are commercially available with novel characteristics. Knowing more about where beer strains came from will help facilitate that.”

For brewers like Bruce Lish, this kind of knowledge is what makes brewing beer interesting after more than 20 years in the business.

“I find it fascinating first of all that people can trace strains down to specific regions of the world. The sky is the limit with your kinds of yeasts you can use and the outcomes you can expect from them. So the more the merrier”

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