The evolution of beer has been explored in research led by University of Wisconsin-Madison graduate student Emily Clare Baker and corresponding author Chris Todd Hittinger. The study was carried out with the aim of completely sequencing the genome of Saccharromyces eubayanus – a newly discovered type of yeast – and determining whether it originated through independent hybridisation.
The original and highly versatile yeast, Saccharromyces cerevisiae, has been in use for millennia in the production of ales, wine and bread. The Saccharromyces eubayanus yeast, which was discovered in Patagonia in just 2011, was compared to Saccharromyces cerevisiae, allowing the researchers to complete genomes of both parental yeast species contributing to lager beer, according to the study published in Molecular Biology Evolution.
Hittinger told IBTimes UK: "Our findings were that those two lineages of lager brewing yeasts that brewists had traditionally divided actually originated through independent hybridisation events. That was a bit of a surprise because there were a few research groups on both sides of the camp as to whether there would be a single origin followed by diversification or those two lineages splitting off from each other or whether it represents independent hybridisations between S. cerevisiae strains or wild S. eubayanyus strains.
"The present analysis comes pretty firmly down on the multiple origins model. The second major finding, in both cases despite the fact that they were starting from different starting points, both lineages experienced a dramatic increase in their rate of evolution which is seen very often in plants and animals.
"You end up going through a small population size and that allows deleterious serials to start to creep in, and what you end up with is an elevation in the rate of mutations that change the protein coding of genes versus neutral changes."
He added in a press release: "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."
The findings clarified the origins of the major lineages of the hybrid yeasts used to brew lagers and will provide a roadmap for future research, which Hittinger said "now provides researchers a way to take cheaper and faster sequencing technologies and map there sequencing references on to that order in order to interpret the origins of other strains".