From America’s Budweiser to Germany’s Munich Helles, lager beer is a staple beverage across the world. Ask any beer aficionado about the difference between a lager and ale, and if he’s worth his salt he will tell you that it’s all about the yeast. While brewers have long known that lager uses a special kind of yeast, exactly what makes this yeast different has long been a mystery.
Chris Todd Hittinger, an evolutionary geneticist at the University of Wisconsin-Madison, is hoping to shed some light on lager yeast, and what makes it different from most other kinds. The Los Angeles Times reported on Aug. 12, that for hundreds of years people used the same kind of yeast to make beer as they did to make wine and beer. This yeast was a species called Saccharomyces cerevisiae (S. cerevisiae).
Around 500 years ago, monks in Bavaria changed the history of beer forever when they began brewing in a cave during winter. These monks had found a new type of yeast that allowed them to create beer at cooler temperatures, producing the first lager. “Brewers typically, even before understanding that yeast was the cause of fermentation, often adopted practices that were sort of conducive to passaging [yeast] strains from one batch of wort to another,” said Hittinger. Wort is the mix of grains that contain the sugars which yeast ferment into alcohol.
As it turns out, the yeast used by the Bavarian monks was not an entirely new, but a hybrid of the S. cerevisiae and a different unknown strain of yeast. Hittinger and his team set out on a several year long, globetrotting trip to locate this unknown strain of yeast and discovered it in 2011, in a very odd location. Saccharomyces eubayanus (S. eubayanus), the mystery yeast, was first found on the sides of beech trees in Patagonia. As the researchers did more work, they found that S. eubayanus was far more common in the Southern Hemisphere than the Northern Hemisphere, with discoveries occurring in odd places like Wisconsin or China.
Since the discovery, Hittinger has been testing the DNA of the two strains of yeast to get a better idea of the history of lager yeast. “Brewers had classically defined two major types of lager yeast: the Saaz lineage, which is not used very much anymore today, and the Frohberg lineage, which is the main lineage of lager yeast that constitutes most of the strains that are used industrially today,” Hittinger said. While Hittinger hasn’t quite figured out how S. eubayanus got to Bavaria, his recent study, published in the journal Molecular Biology and Evolution, details the origins of the two types of lager yeast.
Saaz and Frohberg both began with different strains of S. cerevisiae and eventually hybridized with a similar strain of S. eubayanus resulting in similar but distinct strains of yeast. Over the years, Saaz has fallen to the side as Frohberg has become the yeast of choice for most lager brewers. According to Hittinger, there may be a genetic reason for this, it turns out Saaz is less efficient at fermenting.
Now Hittinger is hoping to expand the kinds of yeast used by brewers, as he believes there might be some strains of yeast out there that could make even better beer than the types we use today. “There’s a lot of diversity that’s been left on the table,” he said of the yeast used by brewers today. “It raises the question: In the entire population, are there additional variants that might be useful?”