For the first time in Europe, scientists have discovered the ancestor of the yeast species necessary for the production of lager beer.
Rewing is one of the oldest human industries, and scientists have uncovered evidence of fermented beverages from China at least 7,000 years ago and from Israel as much as 13,000 years ago.
Modern brewing developed in Europe where, up until the Middle Ages, most beer breweries were associated with a yeast called Saccharomyces cerevisiae.
This type of yeast is still used today to make ale beer, wine and bread.
However, most beer made today is lager and not ale, and there is great interest in understanding the historical shift from one to the other.
Lagers are fermented with a bottom-fermenting yeast at cool temperatures, while ales are fermented with a top-fermenting yeast at much warmer temperatures.
Another species of yeast, Saccharomyces pastorianus, is used in the brewing of beer, which first appeared in Bavaria in the 13th century.
This is a hybrid of two parents, only one of which is S. cerevisiae.
The identity of the second parent was a mystery until 2011, when Saccharomyces eubayanus was discovered in the Patagonian Andes of South America.
Like S. pastorianus, S. eubayanus is cold tolerant.
While records show that S. pastorianus was first used in breweries in southern Germany, the S. eubayanus parent has never been found in Europe.
Instead, researchers have discovered the yeast in South America, North America, China, Tibet and New Zealand.
This caused some researchers to wonder if S. eubayanus had actually ever been to Europe, and if not, where the storage yeast S. pastorianus came from.
But now researchers at University College Dublin have discovered and isolated S. eubayanus in a wooded area on their campus.
Researchers isolated two different S. eubayanus strains from soil samples collected at University College Dublin’s Belfield campus as part of undergraduate research projects to identify wild yeast and sequence their genomes.
The samples are from soil at two locations on the university campus, approximately 17 meters apart, collected in September 2021.
According to the study, the genome sequences of these two isolates showed that they are related to the S. eubayanus ancestral strain that originally mated with S. cerevisiae to form S. pastorianus.
Researchers say the discovery of S. eubayanus in Ireland shows that this yeast is native to Europe and that it is likely to have lived in other parts of the continent.
This new study supports the view that natural populations of the yeast that provided the parents of the first lager yeast existed in southern Germany during the Middle Ages.
The paper’s lead author, Geraldine Butler, University College Dublin, said: “This discovery is a fantastic example of research-led teaching.
“Our students have found over a hundred yeast species in Irish soil samples over the last five years and we are delighted to find S. eubayanus on our own doorstep.
“We’re hoping to find a commercial partner to brew with it so we can find out how it tastes.”
The research results were published in FEMS Yeast Research.
https://www.independent.ie/news/environment/researchers-find-elusive-european-parent-of-lager-yeast-in-ireland-42201375.html Researchers find elusive European parent of lager yeast in Ireland