University of Wisconsin-Madison
Researchers in Patagonia first discovered the yeast Saccharomyces eubayanus on these orange-colored beech tree galls, which are outgrowths caused by infection.
Kirby Nelson isn’t a beer geek. He’s a brewery geek. The brewmaster for Wisconsin Brewing Company, Nelson describes himself as an environmental technician whose job is to create and optimize the ideal configurations of water, barley, hops and yeast — and then let mother nature do the rest.
Barley and hops get most of the credit for giving beer its flavor, but yeast plays an essential role too, creating the alcohol and carbonation through the process of fermentation.
And not all yeasts are created equal. Over the course of his career, Nelson has through experimentation found the strains that perform best for each of the various styles of lager and ale brewed at Wisconsin Brewing Company’s Verona facility. But this fall, he’s going to be testing out something totally new — a recently discovered species of wild yeast native to Wisconsin that could help unlock a whole new category of beer. “This is not a standard yeast that’s been time-proven in any brewery, anywhere,” Nelson says. “It’s a brand new thing, so there’s a learning curve.”
First discovered in 2011, the species is called Saccharomyces eubayanus, and it’s a precursor to the yeast used in lager-style beers. Although the breakthrough is relatively new, the species provides an answer to the centuries-old mystery of how lager yeast developed — and an opportunity to see how the species can be implemented in fermentation science and beyond. “It’s just a fascinating story,” Nelson says. “Being able to work with this stuff is beyond cool.”
Yeast is everywhere — on our bodies, in our food, floating in the very air we breathe. One of the earliest domesticated organisms, the single-celled eukaryotic fungi helped transform humanity when ancient people learned to bake bread — and more importantly, brew beer. Yeast is mentioned numerous times in the Bible, usually representing sin or evil. But medieval English brewers are said to have called it godisgoode — yeast was seen as a gift from God.
For hundreds of years, there have been two known species of yeast for brewing beer: Saccharomyces cerevisiae, used since ancient time for brewing ales, and Saccharomyces pastorianus, a hybrid responsible for the lager style and first recorded in 15th century Bavaria.
Now the most popular style in the world, lager is believed to have developed accidentally when beer-brewing monks began storing barrels of ale in caves. Saccharomyces cerevisiae, which prefers warmer temperatures, merged with another strain in the cool subterranean environment to form the hybrid Saccharomyces pastorianus, which thrives in cooler temperatures. Scientists in the 1980s confirmed the relationship between the two, but the other parent remained a mystery until 2011, when an international team of researchers discovered the missing link in Patagonia: Saccharomyces eubayanus.
UW-Madison genetics professor Chris Hittinger co-authored the study describing the breakthrough. He continued his wild yeast research in Wisconsin, and a few years later, he and a team of students found Saccharomyces eubayanus in a park near Sheboygan, Wisconsin. It was the first — and so far the only — time the species had been identified in North America. “Because Saccharomyces eubayanus has been so rarely isolated from the wild, this is really a unique opportunity for study,” Hittinger says. “It seems to be very rare.”
With Wisconsin’s legacy of German immigrants and strong brewing tradition, testing the yeast’s potential for beer-brewing was a natural fit. And there’s a local food angle there, too. “You locally source barley and hops, but this is an example of a locally sourced microbe,” Hittinger says. “That’s an angle people aren’t often thinking of.”
In its wild, undomesticated form, Saccharomyces eubayanus is not particularly well-suited for industrial-scale brewing. Not much was known about its genetic mechanisms initially, but researchers eventually discovered that the traits relevant to beer brewing are dominant and can be reconstructed in the lab. Since the discovery, researchers in Hittinger’s lab have been working on isolating wild yeast strains and creating hybrids, crossing Wisconsin-native strains with ale strains. “We’re essentially replaying the process of hybridization that occurred hundreds of years ago in some Bavarian cellar,” Hittinger says.
Through experimentation, researchers are starting to get a clearer picture of which genes are implicated in producing traits like cold tolerance, rates of fermentation and the production of flavors. Much of the microbrewing resurgence has focused on hops as a flavoring agent, but different strains of yeast can produce strong flavor differences as well — the traditional German weissbier gets its signature smoky clove flavor from isoamyl acetate, a compound synthesized by yeast. Wild yeasts also tend to produce a crisper, cleaner flavor than domesticated strains, Hittinger says.
Until the discovery of Saccharomyces eubayanus, it was impossible to study the genetic basis of the traits present in various strains of yeast. Now, with the missing ancestor identified, researchers are able to reconstruct the history of how the strains developed and which genes are responsible for which traits. As the understanding of yeast genetics improves, scientists could one day create custom strains that improve or alter particular properties.
This opens an exciting new realm of possibilities for commercial brewers and home brewers alike. “You could imagine, if somebody had a favorite ale strain, we could make a custom lager strain for them,” Hittinger says. “But we’re just at the point where some of those things are starting to be possible. It will be interesting to see if there’s consumer demand.”
The collaboration with Wisconsin Brewing Company will eventually help answer that question, says Monica Theis, interim director of UW-Madison’s fermentation sciences program. “The dream is to come up with a viable product in our brewhouse and then scale it up at Wisconsin Brewing Company,” she says. “It’s really exciting, from the interdisciplinary research and the potential it has to connect people across the whole spectrum of [the] grain-to-glass [movement].”
There are hundreds of varieties of beer yeasts available to choose from, but brewers are always looking for new opportunities to innovate. And while the discovery of a new species of yeast is a big deal in the genetics world, it’s bound to be of interest to brewers as well. Nick Smith, the associate outreach specialist for UW-Madison’s fermentation sciences program, says there’s growing interest in the use of non-typical yeast for making wine and beer. “There certainly is a trend,” he says. “People are creating new types of products, or they’re bringing back old styles.”
College of Agricultural and Life
Locally grown! UW-Madison genetics professor Chris Hittinger (left) and research intern Kayla Sylvester with a few of their test tubes and petri dishes of wild yeasts.
As an intermediary between the yeast genetics work happening in the Hittinger laboratory and the hands-on brewery experiment, Smith hopes to identify high-quality strains that will eventually help breweries develop new and interesting products to add to their existing portfolios. There’s an entire library of wild yeast strains to choose from waiting to be studied and analyzed based on their metabolic rate, their preferred temperature and environment for fermentation and the kinds of flavors and aromas they produce. Learning how yeast performs is essential if you’re going to incorporate it into a commercially brewed beer. Preliminary test batches with Saccharomyces eubayanus have showed that it’s a slow fermenter that doesn’t consume all the sugar the way that a normal brewer’s yeast would.
“It’s a different yeast, so understanding how to ferment and brew with it is proving a little bit challenging,” Smith says.
This wild yeast project is an offshoot of Campus Craft Brewing, a partnership launched in 2014 between Wisconsin Brewing Company and UW-Madison’s Department of Food Science that gives fermentation sciences students an opportunity for hands-on experience in a brewery setting. The collaboration happened after Nelson was invited to speak to students in an advanced brewing class. The students invited him to check out their brewing equipment (a 40-liter system donated by MillerCoors) and sample their latest creation, a milk stout made with lactose from the campus dairy cows. “The beer was really good,” Nelson recalls. His plan to produce a big run of the milk stout never materialized, but the idea turned into a partnership with students who have since produced a number of brews including a grapefruit radler, an American pale ale, an American wheat ale, and a red lager.
It’s great experience for the brewers in training, but Nelson has found the collaboration beneficial as well. “These folks are just scary intelligent,” he says of the students. “Even though they’re approaching things from a rookie stance, they have some interesting perspectives on how to do things. I’ve learned a lot from them.”
Within the next month or so, Nelson and the UW-Madison students will start brewing with different yeast strains, comparing them side by side with the goal of finding something that works well enough to create a new beer suitable for large-scale commercial production. “We did a quick brew, and it’s very interesting,” Nelson says. “Almost like a lager with Belgian ale characteristics.”
To evaluate the different yeast strains, Nelson is planning a series of experimental brews. Using identical environmental conditions, he will introduce various strains of yeast into the wort and take note of how long it takes to consume the sugar, how the yeast settles out and how the finished product tastes. There’s no set timeline for when the new beer will be commercially available, but Nelson says he’ll post updates on the Wisconsin Brewing Company Facebook page. “By trial and error, we’re going to narrow it down,” he says.
Wisconsin Brewing Company and Campus Craft won’t be the first ones to create a brew with Saccharomyces eubayanus. Earlier this year, Heineken debuted a new, limited edition beer called H41, named for the longitudinal coordinate of where the yeast was first discovered in Patagonia. But Campus Craft will be the first to brew with the strain found in Wisconsin. How’s that for hyperlocal?
Says Nelson: “Hell, we’re Wisconsin Brewing Company — what could be more Wisconsin than using the precursor to modern-day lager yeast that thrives right here in Wisconsin?”
