University of Wisconsin-Madison researchers have confirmed the origins of cold-adapted yeast that is used to produce the most popular beer in the world - "Lager."

Lager beer is one of  the most widely consumed and commercially important beverages in the world. It is produced through fermentation and brewing at low temperatures.

In a 2011 study, scientists identified a type of South American yeast that was claimed to be one of the ancestors of the cold-adapted yeast. The South American yeast somehow arrived at Bavaria, Germany from Patagonia (South America), where it was combined with the domesticated Old World yeast (known for making ale and bread) to form the hybrid that is used to make lager or cold stored beer.

The new study has backed the claims made in the 2011 study.

The new findings suggest that Saccharomyces eubayanus, native Patagonian yeast, was one of the ancestors of the hybrid yeast used in lager production. When the researchers analyzed the yeast's genetic sequence, they found that the cold-loving microbe was closely related to one of two highly diverse Patagonian populations. About 500 years ago, the researchers believe the South American yeast made its way to Bavaria, where lager beer was first concocted.

"This yeast really is native to Patagonia," said Chris Hittinger, a professor of genetics, in a press release. "We found two major populations that seem to be distinct. The trees they're associated with seem to provide everything they need. They're happy there."

Despite their abundance in Patagonia, the new study has found that Saccharomyces eubayanus is not just limited to South America. Researchers found the yeast in Indian Mound Park, near Sheboygan, Wis. It is the first time that the microbe has been discovered outside of Patagonia. The researchers said that the yeast must have been accidentally introduced to the North American soil, similar to the way an ancestor travelled to Europe and triggered the production of cold-brewed lager beer.

"Yeasts are important for fermenting processes and biotechnology," genetics graduate student David Peris, and a co-author of the new study, said. "The value of studying diversity is that you can pull out genes or strains that can be used for a particular industrial process."

"The idea," Hittinger said, "is to tap into biodiversity and find the strains that ferment better and those strains, or their genes, can be plugged into industrial processes."

The findings are published in the journal Molecular Ecology.