Saccharomyces eubayanus

Lager is a type of beer created from malted barley and fermented at low temperatures, originally in Bavaria. S. eubayanus was first discovered in Patagonia, possibly being an example of Columbian exchange, and is capable of fermenting glucose, along with the disaccharide maltose at reduced temperatures.

History

With the emergence of lager beer in the XVth century, S. eubayanus was considered to be the progenitor of S. pastorianus along with S. cerevisiae. Since 1985 the non-cerevisiae ancestor has been contentiously debated between S. eubayanus, and S. bayanus which "is not found outside the brewing environment". Upon the 2011 discovery of S. eubayanus in Argentina and consequential genome analysis, S. eubayanus was found to be 99% genetically identical to S. pastorianus and S. bayanus was dismissed as an ancestor.

First described in 2011, S. eubayanus was discovered in North Patagonia, ecologically associated with Nothofagus spp. (Southern Beech) forests and the parasitic biotrophic fungi Cyttaria spp. With discoveries in other parts of the world shortly after in east Asia, the South American origins of S. eubayanus have been challenged by genomic and phylogenetic evidence that suggests a Tibetan origin. The proponents of this theory argue that it "corresponds better with geography and world trade history" given the Eurasian land bridge. Since then, genomic analyses from South America strains have shown reduced genetic diversity suggesting a biogeographical radiation point from Patagonia.

In 2022, a researcher team from the University College Dublin isolated Saccharomyces eubayanus from soil samples in Ireland. Further isolations from different locations in Europe can be expected.

Phylogenetically, S. eubayanus is basal in the Saccharomyces genus, and well-adjusted to the cooler environment of Nothofagus forests, Saccharomyces species with thermo-tolerance are suggested to be derived traits.