Ask any brewer and they will tell you that yeast is the secret to making beer. A fungus that works to break down the sugars in the grains used in brewing, yeast creates both the alcohol and the unique flavors and aromas of different beers. Not all yeast, though, works the same. For instance, ales use S. cerevisiae, a type of yeast that is called a “top fermenter” because after it has completed its job, the yeast rises to the top of the beer. But other strands of yeast like S. pastorianus create lagers and are called “bottom fermenters” because they sink to the bottom of the beer they produce.
The origin of lagers’ yeast, though, has been a mystery. S. pastorianus is actually a hybrid. It descends from S. cerevisiae and another yeast called S. eubayanus. It is from this second yeast that S. pastorianus inherited the ability to ferment at lower temperatures, but for years, scientists couldn’t find S. eubayunus in Europe, the birthplace of the modern lager.
However, in 2022, a group of undergraduate students at University College Dublin participating in a class activity discovered local strains of the missing yeast. The students had dug soil samples from the university campus and then allowed the naturally occurring yeast to grow so that they could later practice the basics of genome sequencing. Instead of finding more expected varieties of yeast, the students stumbled upon a missing link in an important part of culinary and cultural history: S. eubayanus. Scientists have yet to discover when S. eubayanus arrived in Germany but finding it in Europe is a big step toward understanding the history of lagers.
