(CSULA-UT) After decades, scientists found an elusive species of yeast in the forests of Argentina that was key to the invention of crisp tasting German beer 600 years ago. 
A five year search around the world by a scientific team lead to the identification and name of the organism, a species of wild yeast called Saccharomyces eubayanus, living on the 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.
It's believed that S. eubayanus  found its way to Europe and hybridized with domestic yeast used to brew ale, thus creating a new organism that fermented at a lower temperature to make lager. 
Searching through collections of wild yeasts from Europe, researchers 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.
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.
The yeast was brought to a lab at the University of Colorado and analyzed. The team 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 researchers compared the DNA of the wild Patagonian yeast with that of lager yeast used in breweries to see what changes had evolved over the years. They found changes in genes that regulate sugar and sulfite metabolism, processes that contribute to the fermentation and preservation of beer.
"Scientists could exploit such knowledge to improve biofuels," Hittinger said.
And, of course, tinkering with yeast genes might make wine or beer taste better too, said Hittinger, who is "a lager man" himself. Coauthor Mark Johnston, a molecular biologist at the University of Colorado School of Medicine, prefers ales.
"Even though we both stand by our original preferences, we both have a new appreciation for where lager came from and the complexity of the processes that made it what it is today," Hittinger said.

< Prev		Next >