Using novel sequencing techniques, a team of US researchers have traced the origins of the yeast used in making most popular lager beer all the way back to 15th century Bavaria in southeastern Germany.
As any beer snob worth their salt will tell you that a good brew depends largely on the quality of the yeast – but what exactly do we know about the evolution of the fungal organisms frequently used as ingredients in the various ales and lagers enjoyed the world over? The original yeast called Saccharomycescerevisiae was used to create wine, ales and bread, claim the scientists.
The result was a lighter and smoother beer which, after being shared their neighbouring Bohemians, went on to dominate 19th and 20th century beer tastes, especially in America.
Genetic studies suggest at least two distinct hybridization events between almost identical strains of S. eubayanus, with relatively more diverse ale strains of S. cerevisiae, says University of Wisconsin-Madison evolutionary geneticist Chris Todd Hittinger.
Presently, lagers represent an overwhelming 94 percent of the global beer market.
Researchers from the University of Wisconsin-Madison were able to clone a genome of S eubayanus employing the next-generation sequencing bio-technology. The researchers have made its comparison to domesticated hybrids that have been used for brewing lager and that has allowed the ability of studying the entire genomes of both the parental yeast species that have contributed to lager beer for the first time ever. But for more than 500 years no one knew what kind of yeast they used to produce it.
Hittinger stated that brewers often adopted procedures that appeared to be conducive to passage different yeast strains from one batch of worts to another even before knowing that yeast was the primary factor responsible for triggering fermentation.
“There were two major hypotheses about the origins of the Saaz and Frohberg groups, [and] there was some prior support for each, so both models were plausible”, he added via email. Over the years, Saaz has fallen to the side as Frohberg has become the yeast of choice for most lager brewers. Since each lineage had different ratios of S. eubayanus and S. cerevisiae, the scientists determined that the two yeasts mixed, or hybridized, multiple times as they evolved.
He finally pointed out that despite the fact these hybrids had been different from the start, they did change in a predictable manner during their domestication. The Bavarian monks discovered a new yeast type, which could be used to make beer at low temperatures.
In addition, since being adapted for beer making, the S. eubayanus genomes have experienced increased rates of evolution, including in some genes involved in metabolism.
Regarding the strains of yeast utilized in industrial-scale brewing today, “there’s a lot of diversity that’s been left on the table”, he noted.