Saccharomyces eubayanus means Beer!

How did lager beer come to be? After pondering the question for decades, scientists have found that an elusive species of yeast isolated in the forests of Argentina was key to the invention of the crisp-tasting German beer 600 years ago.

It took a five-year search around the world before a scientific team discovered, identified and named the organism, a species of wild yeast called Saccharomyces eubayanus that lives on beech trees.

“We knew it had to be out there somewhere,” said Chris Todd Hittinger, an evolutionary geneticist at the University of Wisconsin-Madison and a coauthor of the report published Monday in the Proceedings of the National Academies of Sciences.

Their best bet is that centuries ago,S. eubayanus somehow found its way to Europe and hybridized with the domestic yeast used to brew ale, creating an organism that can ferment at the lower temperatures used to make lager.

Geneticists have known since the 1980s that the yeast brewers use to make lager, S. pastorianus, was a hybrid of two yeast species: S. cerevisiae — used to make ales, wine and bread — and some other, unidentified organism.

Searching through collections of wild yeasts from Europe, researchers — including Hittinger and his collaborators — tried to identify lager’s missing link but again and again were stumped. “There were a few candidates, but none fit particularly well,” Hittinger said.

So he and his colleagues began “sampling more systematically,” collecting soil and bark, sap and abnormal growths called galls from trees on five continents.

Team member Diego Libkind of the Institute for Biodiversity and Environment Research in Bariloche, Argentina, found S. eubayanus in galls on southern beech trees in Patagonia. The galls were particularly rich in sugar, which yeast like to colonize and consume.

Patagonian natives used to make a fermented beverage from the galls — a definite clue that the scientists were on the right track, Hittinger said.

When the team brought the yeast to a lab at the University of Colorado and analyzed its genome, they discovered that it was 99.5% identical to the non-ale portion of the S. pastorianusgenome, suggesting it was indeed lager yeast’s long-lost ancestor.

“The DNA evidence is strong,” said Gavin Sherlock, a geneticist at Stanford University who has studied lager yeast but was not involved in this study.

But Sherlock wondered how S. eubayanus could have traveled the nearly 8,000 miles from Argentina to Germany.

“We all know that in 1492, Columbus sailed the ocean blue,” he said. “Lager was invented in the 1400s. It’s not really clear how that progenitor would have gotten from South America to Europe.”

Scientists may yet find colonies of the yeast in Europe, he said. Another possibility is that lager yeast originated a bit later(more)than previously thought, added Barbara Dunn, a senior research scientist who works in Sherlock’s lab.

Leave a Reply

Your email address will not be published. Required fields are marked *