A discovery by a student in Ireland fills a gap in lager history

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men 2011 one a mystery in brewing history has been replaced by another. The secret to solving was where the specialist yeast needed to make lager came from. The new one was how he got to Lager’s background and originsouthern Germany – because that yeast was found in Patagonia.

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Lager seems to have started sometime around the 15th century. Before that, all European beer was ale. The difference is that lager ferments and ages in cool conditions, so it must Saccharomyces pastorianus, a cold-tolerant yeast species, for its production. Ales ferment closer to room temperature. That needs another meat, S. cerevisiaewith other versions used by bakers for sourdough bread.

S. pastorianus he himself, however, is a combination of S. cerevisiae and something else. That was what appeared in 2011, in shape S. eubayanus, discovered by Todd Hittinger of the University of Wisconsin-Madison and Diego Libkind of the Argentine National Council for Scientific and Technical Research. And that raised the interesting question of how this fungus had traveled from Argentina to central Europe before Christopher Columbus made his first trip to America in 1492.

seek and ye shall find. Since it was first discovered, S. eubayanus turned up elsewhere. Although its phylogenetic tree shows that it actually originated in Patagonia (it probably preferred the cold, an adaptation that encouraged it to live there during the last Ice Age), it was also found in North America, China and New Zealand – spread, apparently, through natural processes such as blowing in the wind, or hitting migratory birds and insects.

But it hadn’t been seen in Europe – at least, not until Stephen Allen, a student at University College Dublin, collected yeast samples from a wooded area of ​​one of the college’s campuses as part of a research project under -step, cultured them, and did a preliminary genetic study.

When the results came back, Geraldine Butler, his supervisor at the school of biomolecular and biomedical sciences, thought she saw S. eubayanus‘signature inaccessible. “I had a hard time convincing the other employees that we could have eubayanus, it seemed so unlikely,” she says. But a complete genetic sequence confirmed it. Dr Butler, Mr Allen and their colleagues published their findings this week inFEMS Yeast Research.

Dr Butler says the study shows that today’s lager yeast is indeed closely related to the Irish species, as well as to a previously discovered Tibetan version. The short set that ran in 2011 has not quite caught on. Neither the Irish nor the Tibetan are close enough to be the direct parent of lager yeast. But the hunt is now, at least, given to Europe. The game is on.

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