Long ago, in Bavaria, beer underwent a transformation. Dark ale evolved into a paler, more golden drink, and became much more common around the time a ducal edict restricted brewing to the winter months. The lager, as the new beer was called, had begun its path to world domination.
Centuries later, geneticists have discovered that the yeast responsible for fermenting lagers is a hybrid of traditional brewer’s yeast and another cold-hardy yeast, Saccharomyces eubayanus. The lager yeast appears to be the result of a chance cross in a cold brewery, where the low temperatures allowed the hybrid to thrive.
But while brewer’s yeast is common, it’s been harder to trace how the other mother yeast ended up in Bavaria. It was first seen in the wild in 2011, when biologists discovered the cold-loving yeast, S. eubayanus, in the forests of Patagonia in South America. Some traces were then found in the Italian Alps, Tibet, western China and North Carolina.
Sightings in Europe have been almost non-existent. But in a recent article in the journal FEMS Yeast, biologists reported finding S. eubayanus living in the soil on the University College Dublin campus in Ireland, in the form of a pair of strains apparently from the same branch of the family as versions found in Tibet and North Carolina.
The finding is consistent with climate modeling that suggests Ireland would be a hospitable environment for yeast, said Chris Hittinger, a professor of genetics at the University of Wisconsin, Madison, who was part of the team that found the yeast in Patagonia. What is less clear is why the yeast is so hard to find in the wild beyond South America, where it is thought to be an endemic species.
Discovering S. eubayanus in more places may help researchers see how its genetic diversity varies, which could shed light on how a yeast from South America found its way around the world to help fuel lager brewing in Bavaria.
“There is doubt about the route,” said Geraldine Butler, professor of genetics at University College Dublin. “Tibetan is a slightly closer relative of lager yeast than Irish,” suggesting that the yeast may have reached Germany via Asia.
The yeast could have traveled overland long before humans came on the scene, perhaps traveling on birds and insects, Hittinger said. Butler’s group will continue to search for S. eubayanus on their campus.
“We are interested in seeing what kind of beer it will produce,” Butler said.
By: VERONIQUE GREENWOOD
BBC-NEWS-SRC: http://www.nytsyn.com/subscribed/stories/6500865, IMPORTING DATE: 2022-12-19 21:40:05
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