Modern Beer Yeast Is a Mixture of Strains Used to Make Grape Wine and Asian Rice Wine

beer, glass, yeast
What are the origins of modern beer yeast? Justin Sullivan/Getty Images

The species of yeast known as Saccharomyces cerevisiae—often referred to as "brewer's yeast"—has been harnessed by humans since ancient times; with different strains used to make various types of beers, wines and baked products. Nevertheless, the origins of the strains that are used to make beer today have long remained unclear.

To shine a light on this issue, a team of researchers led by Justin Fay from the University of Rochester have investigated the ancestry of these beer strains, finding that they are actually derived from a mixture of varieties used to make European grape wines and Asian rice wines.

The findings—which are published in the open-access journal PLOS Biology—suggest that there was a transfer of fermentation technologies between East and West at some point in history, which led to the creation of modern beer-brewing yeast.

Yeasts—of which there are around 1,500 species—are single-celled microorganisms that ferment carbohydrates into carbon dioxide and alcohols. They are very common in the natural environment but are also probably one of the earliest domesticated organisms, despite the fact that ancient peoples had not yet discovered microbes.

Normally, when scientists want to investigate the historical origins of domesticated organisms, they perform DNA analysis. However, this is tricky to do with yeast because ancient fermented beverages and the microbes used to produce them tend to have been lost to time. Furthermore, with modern beer strains, there are no obvious wild populations from which they could have been derived.

So, to determine the ancestry of modern beer strains, the scientists made use of the fact that many are known to be "polyploid"—that is, they have more than two sets of chromosomes, thread-like structures in cells that carry genetic information. This was particularly helpful to the researchers.

"Similar to both lager and baking strains, ale strains are polyploid, providing them with a passive means of remaining isolated from other populations and providing us with a living relic of their ancestral hybridization," the authors of the study wrote.

For their research, the team compared the genomes—the complete set of genetic material in an organism—of beer yeast strains to those of reference strains isolated from diverse sources and geographic locations.

"We found ale, baking, and the S. cerevisiae portion of lager strains to have ancestry that is a mixture of European grape wine strains and Asian rice wine strains," the authors wrote in the study. "This admixture suggests that early industrial strains spread with brewing technology to give rise to modern beer strains, similar to the spread of domesticated plant species with agriculture."