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Third-year genetics student Stephen Allen discovered a yeast isolate in Irish soil that had not been found naturally in Europe – until now.
An undergraduate student at University College Dublin (UCD) has stumbled upon an interesting discovery involving one of the parents of the yeast hybrid that is used to make lager.
While studying soil samples taken from the UCD Belfield campus, third-year genetics student Stephen Allen was able to identify a type of yeast that had not been found naturally in Europe until now.
This yeast isolate, Saccharomyces eubayanus, is one of two types of yeast that gave birth to the hybrid yeast Saccharomyces pastorianus, which has been used to make lager since the 15th century.
Humans have been brewing beer for thousands of years. The most common types of beer until the invention of lager were ales and stouts – brewed using a yeast isolate called Saccharomyces cerevisiae.
Lager became popular in 15th century Bavaria with the appearance of the hybrid yeast. One of the parents of this hybrid has long been identified as Saccharomyces cerevisiae, but the other parent had eluded scientists for nearly 300 years.
The second parent, Saccharomyces eubayanus, was discovered in 2011 in Patagonia, South America. Only a few strains of this variant have been found outside South America – including traces in the Himalayas, China, North America and Australia.
After the discovery of Saccharomyces eubayanus in Irish soil, Europe can now be added to this list.
“It is assumed that S. eubayanus hybridised with S. cerevisiae somewhere in Europe during the Middle Ages, but European isolates have never been found until now,” said Prof Geraldine Butler of the UCD School of Biomolecular and Biomedical Science, who was involved in the research.
“It suggests that natural populations were in Bavaria in the 15th century, enabling them to hybridise with S. cerevisiae to make the first lagers. The Irish discovery will invigorate searches for similar yeast isolates elsewhere in Europe.”
While Allen made the initial discovery, a group of UCD academics and students were involved in the research published around it. The team is now exploring the possibility of using the yeast to brew beer in labs as well as with a commercial brewer.
Butler added that Allen’s discovery is a “fantastic example of research-led teaching”.
“Our undergraduate students have isolated hundreds of different yeasts from Irish soil samples. By finding S. eubayanus in Europe, Stephen has solved a longstanding puzzle about how lager yeasts originated.”
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