The ancestor of modern brewing yeast has been found hiding in Ireland

In 1516, the Duchy of Bavaria in Germany imposed a law on its breweries with the goal of keeping ingredients such as wheat and rye for baking bread. The ordinance limited brewers to using only barley, hops, water and yeast to make libations, and set beer prices depending on the time of year. Law inadvertently limited the fermentation process to winter, which favored a cold-tolerant yeast called Saccharomyces Pastorianuswhich brews beer, most commonly S. cerevisiae, who brews beer.

S. Pastorianus It is a hybrid, produced by mating S. cerevisiae With another yeast called S. eubayanus. Despite the beer’s European origins, S. eubayanus It was not actually found there and was only discovered for the first time in 2011. in the Patagonia region of South America (SN: 8/23/11). Now, thanks to a research project conducted by undergraduate students, S. eubayanus They are found living in European soil — fittingly, in the beer-loving country of Ireland.

since discovery S. eubayanus [more than] “10 years ago, it was fun to group places where species existed together,” said Quinn Langdon, a Stanford University biologist who was not involved in the study.

The leading theory is that S. eubayanus It originated in Patagonia and then spread around the world, eventually interbreeding with it S. cerevisiae in European breweries to make it S. Pastorianus.

Geraldine Butler, a geneticist at University College Dublin and leader of the project, has long believed that teaching genome sequencing techniques by having students scavenge soil for yeast could emerge. S. eubayanus. However, she says, she couldn’t contain her excitement when she saw the first hint of the microbe. “I was sitting next to the sequencer waiting for the results to come in,” she says.

One of Butler’s students, Stephen Allen, found two local strains of S. eubayanus They hide in plain sight on the Belfield campus of University College Dublin. The team has since gone back and found the yeast again, Butler says, indicating a stable population of yeast living in Irish soil.

The new discovery was published on December 7 in the FEMS Yeast Research.

Butler hopes the discovery will spark interest elsewhere in Europe to search for it S. eubayanus, including Bavaria, where beer brewing is believed to have first begun. It is also looking for business partners to try brewing Irish-brewed beers.

Langdon isn’t as confident that the new microbes will lead to tasty drinks because there are others S. eubayanus The strains do not grow well on maltose, which is the sugar that must be digested by the yeast during the fermentation process. However, Langdon says, “It would be fun to prepare with them.”

Whether the newly discovered irish subspecies of S. PastorianusGood parent loss or not, there’s no denying that their discovery helps solve a small part of the puzzle over the origins of beer brewing. This 16th-century turnaround from S. cerevisiae to me S. Pastorianus It led to a global turnaround that continues to this day – more than 90 percent of the beer sold worldwide today is lager.

Fungi are the “forgotten kingdom,” Langdon says, and they don’t get as much attention as plants or animals, despite playing a huge role in human history. “Yeast is just single cells that live in the soil, doing really important things.”

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