Long ago, in Bavaria, a change took place in beer. Dark ale evolved into a paler, more golden drink, and became much more common around the time a ducal edict prohibited brewing for the winter months. Lager, as the new beer was called, had begun its path to world domination.
Centuries later, geneticists discovered that the yeast responsible for fermenting lagers is a hybrid of traditional brewer’s yeast and another cold-hardy yeast, Saccharomyces eubaynus. Lager yeast appears to be the result of a chance cross in a cool brewery, where the low temperatures allowed the hybrid to flourish.
But while brewer’s yeast is common, it has been difficult to trace how the other mother’s yeast ended up in Bavaria. It was first observed in the wild in 2011, when biologists found a cold-loving yeast, S. Eubianus was discovered. 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 FEMS Yeast Journal, biologists found S. eubainus to be a pair of strains apparently from the same branch of the family, as found in var. Tibet and North Carolina.
The finding is consistent with climate modeling that suggests Ireland would be a hospitable environment for the 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 outside of South America, where it is considered an endemic species.
In many places S. ubainus could help researchers see how its genetic diversity varies, which could shed light on how a yeast from South America spread around the world to help make fuel in Bavaria. I found my way.
“There is skepticism about the pathway,” 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.
Hittinger theorized that yeast could have traveled overland long before humans arrived on the scene, perhaps traveling on birds and insects. Butler’s group in their compound S.O. Will continue to search for Eubianus.
“We’re interested to see what kind of beer it will produce,” Butler said.