500 years ago, yeast's epic journey gave rise to lager beer

(PhysOrg.com) -- In the 15th century, when Europeans first began moving people and goods across the Atlantic, a microscopic stowaway somehow made its way to the caves and monasteries of Bavaria.

by Terry Devitt

The stowaway, a yeast that may have been transported from a distant shore on a piece of wood or in the stomach of a fruit fly, was destined for great things. In the dank caves and monastery cellars where 15th century brewmeisters stored their product, the newly arrived yeast fused with a distant relative, the domesticated yeast used for millennia to make leavened bread and ferment wine and ale. The resulting hybrid - representing a marriage of species as evolutionarily separated as humans and chickens - would give us lager, the clear, cold-fermented beer first brewed by 15th century Bavarians and that today is among the most popular - if not the most popular - alcoholic beverage in the world.

And while scientists and brewers have long known that the yeast that gives beer the capacity to ferment at cold temperatures was a hybrid, only one player was known: Saccharomyces cerevisiae, the yeast used to make leavened bread and ferment wine and ale. Its partner, which conferred on beer the ability to ferment in the cold, remained a puzzle, as scientists were unable to find it among the 1,000 or so species of yeast known to science.

Now, an international team of researchers believes it has identified the wild yeast that, in the age of sail, apparently traveled more than 7,000 miles to those Bavarian caves to make a fortuitous microbial match that today underpins the $250 billion a year lager beer industry.

Writing this week (Aug. 22) in the Proceedings of the National Academy of Sciences, researchers from Portugal, Argentina and the United States describe the discovery of a wild yeast in the beech forests of Patagonia, the alpine region at the tip of South America, that apparently solves the age-old mystery of the origin of the yeast that made cold-temperature fermentation and lager beer possible.
"People have been hunting for this thing for decades," explains Chris Todd Hittinger, a University of Wisconsin-Madison genetics professor and a co-author of the new study. "And now we've found it. It is clearly the missing species. The only thing we can't say is if it also exists elsewhere (in the wild) and hasn't been found."

Orange-colored galls, such as these pictured in 2010, from the beech tree forests of Patagonia have been found to harbor the yeast that makes lager beer possible. Five hundred years ago, in the age of sail and when the trans-Atlantic trade was just beginning, the yeast somehow made its way from Patagonia to the caves and monastery cellars of Bavaria where the first lager beers were fermented. Photo: Diego Libkind, Institute for Biodiversity and Environment Research, Bariloche, Argentina...

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