In a new paper published by Oxford University Press and FEMS Yeast Research, scientists say they have found, for the first time in Europe, the ancestor of the yeast species needed to make lager beer.
Brewing beer is one of the earliest human activities. Researchers have found evidence of fermented drinks dating back as far as 13,000 years in Israel and at least 7,000 years in China. Up to the Middle Ages, the majority of beer production in Europe was attributed to a yeast known as Saccharomyces cerevisiae. This is where modern brewing originated. Today, ale-style beer, wine, and bread are still made using the same kind of yeast.
However, the majority of beer produced today is lager, not ale, and there is a strong interest in understanding the historical transition from ale to lager in Europe. The yeast used in lager brewing, Saccharomyces pastorianus, originally emerged in Bavaria in the 13th century.
S. pastorianus is a hybrid of two parents, only one of which is S. cerevisiae. Up until 2011, when Saccharomyces eubayanus was found in the Patagonian Andes of South America, the identification of the second parent remained a mystery.
S. eubayanus, like S. pastorianus, can withstand low temperatures, and researchers think that the lager-style of cold brewing favorably influenced the development of the S. pastorianus hybrid yeast from an ale strain of S. cerevisiae and a wild S. eubayanus isolate.
Even though S. pastorianus was first used in breweries in southern Germany, its parent, S. eubayanus, was never found in Europe.
Instead, scientists have found the yeast in North America, China, Tibet, New Zealand, and South America. Some scientists were intrigued by this and began to question whether or not S. eubayanus had ever even reached Europe.
If not, they reasoned, then where did the lager yeast S. pastorianus originate from?
Now, however, University College Dublin researchers have identified and isolated S. eubayanus in a forested section of their campus.
From soil samples taken on the University College Dublin Belfield campus as part of student research initiatives to find wild yeasts and sequence their genomes, the Irish scientists identified two distinct strains of S. eubayanus.
The isolates were found in soil that was collected in September 2021 from two locations on the university campus that were roughly 17 meters apart. These two isolates’ genome sequencing revealed that they are linked to the original S. eubayanus strain that mated with S. cerevisiae to create S. pastorianus.
The finding of S. eubayanus in Ireland demonstrates that this yeast is indigenous to Europe, and it is probable that it has existed in other regions of the continent.
This new study backs up the idea that there were natural populations of the yeast in southern Germany in the Middle Ages, and that these were the parents of the first lager yeast.
Unanswered is the issue of whether these ancient populations remain hidden someplace in the woodlands of Bavaria.
“This discovery is a fantastic example of research-led teaching,” remarks lead author, Geraldine Butler. “Our undergraduates have found more than a hundred yeast species in Irish soil samples over the past five years, and we’re delighted to stumble across S. eubayanus on our own doorstep. We’re hoping to find a commercial partner to brew with it so we can find out what it tastes like!”
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