A recent pint at Silver Branch Brewing Company turned into a history lesson involving trans-Atlantic exploration, the Columbia Exchange, and the genetics of German lager yeast. In general, I prefer German Pilsners over the Bohemian versions most likely for their breadier and lower hop profile. Thus when faced with these two versions at Silver Branch I chose the Vespucci Connection, a dry-hopped German styled pilsner, instead of their Czech Glass Castle Pilsener. I then learned how the Vespucci Connection received its name and the discovery of how German lager yeast evolved during the general lager renaissance of the early 16th century. Brewer’s yeast is generally categorized as “ale yeast” and “lager yeast”. As most people probably know, the scientific name for ale yeast is Saccharomyces cerevisiae. Less commonly known is that the scientific name for lager yeast is Saccharomyces pastorianus. Interestingly, S. pastorianus is a hybrid of S. cerevisiae and an until-recently unknown cold-tolerant yeast–while S. cerevisiae has 2 sets of chromosomes, S. pastorianus has 3 sets. Ale yeast generally prefers a warmer fermentation temperature, and lagers are as clean and crisp as they are because of the colder fermentation temperatures permitted by the contributions of the extra set of chromosomes from the cold-tolerant yeast to the modern lager yeast hybrid. A 2011 study published in the Proceedings of the National Academies of Sciences by Libkind et al determined that the cold-tolerant parent strain of lager yeast is called Saccharomyces eubayanus, and S. eubayanus has only been found in the wild, despite a lot of searching, in Patagonia. Vespucci Connection, Columbian Exchange: The New-world Origins Of Old-world Lager Yeast
Thus it appears that this wild yeast from Argentina's Patagonia region hopped aboard a ship exploring the continent. Since Americo Vespucci was the first to identify South America as a separate continent, it may have been his ship that brought S. eubayanus to Europe where it eventually merged with S. cerevisiae in a cold Bavarian cave. The Columbia Exchange is the term historians use to describe the flow of plants, animals, technology, and diseases between the two worlds. One can press it even forward and suggest that the Beer Purity Law (Reinheitsgebot) of 1516 was also a result of this exchange.
