Using cutting edge DNA sequencing techniques, scientists have traced the origins of yeast that was used to make lager by 15th century Bavarians.
Beers are either ales and lagers. A versatile yeast called Saccharromyces cerevisiae has been used for centuries to make ales, as well as wine and bread.
But a second beer innovation was lager beer during the 15th century, when Bavarians first saw that beer stored in the caves during the winter continued to ferment. Lager comes from the German lagern: to store.
The result was a lighter and smoother beer that, after sharing it with their neighboring Bohemians, went on to dominate 19th and 20th century beers tastes, especially in America. They now represent 94 percent of the global beer market.
Lager yeasts are hybrid strains, made of two different yeast species, S. cerevisiae and S. eubayanus, but the exact origins of different hybrid lineages has been a subject of hot debate for lager beer makers.
Attempting to solve the mystery, a research team from University of Wisconsin-Madison assemble a high-quality genome of S. eubayanus using next-generation sequencing. Comparing it to domesticated hybrids that are used to brew lager style beers, they identified two independent origin events for S. cerevisiae and S. eubanyus hybrids that brew lager beers.
Said corresponding author Chris Todd Hittinger of the University of Wisconsin-Madison:
“Lager yeasts did not just originate once. This unlikely marriage between two species, genetically as different from one another as humans and birds, happened at least twice. Although these hybrids were different from the start, they also changed in some predictable ways during their domestication.”
Mitochondrial genome sequences proved that S. eubayanus served as the main donor of mtDNA for lager yeasts of Frohberg lineage. They also found that both the Saaz and Frohberg yeasts contained both S. cerevisiae (99.57 percent identical to strain S288c) and S. eubayanus (99.55 percent identical to FM1318) genomes.
They also compared the mitochondrial genomes and found S. eubayanus to be 6.6kb smaller than Frohberg yeast and 21.8kb smaller than S. cerevisiae.