Bottoms up as UCC experts help discover chance event that led to world's most popular beer

It has been known for several years that saccharomyces pastorianus — the yeast responsible for producing lager beer — is a hybrid species that arose in Germany from the mating of a top-fermenting ale yeast with a cold-tolerant bottom-fermenting strain, probably around the start of the 17th century. File picture

Researchers are set to down a few well-earned pints after discovering the origin of the world’s most popular beer, with a theory that has turned the brewing world on its head.

And like most good origin stories, it involves political power plays, death, and some strange mating behaviour in a warm, dark space swirling with alcohol.

It has been known for several years that saccharomyces pastorianus — the yeast responsible for producing lager beer — is a hybrid species that arose in Germany from the mating of a top-fermenting ale yeast with a cold-tolerant bottom-fermenting strain, probably around the start of the 17th century.

But the details have been shrouded in mystery and a fair bit controversy — in the brewing world anyway.

Now, a team of scientists from University College Cork (UCC) and the Technical University of Munich in Germany has pinpointed not just where and how, but exactly when it happened — leaving brewing aficionados frothing at the mouth for more.

Thanks to an extensive trawl of ancient Central European brewing records, they believe the hybrid was created by the introduction of a top-fermenting yeast into a brewing environment where the other yeast was present, and not the other way around, as had been thought.

In a paper published in the peer-reviewed Journal FEMS Yeast Research on Wednesday night, they explain how a famous Bavarian brewing rule in 1516 stipulated that only bottom-fermentation was permitted, but that changed in 1548 when the powerful nobleman Hans VI von Degenberg was granted a dispensation for top fermentation.

But when his grandson, Hans VIII Sigmund, died without an heir in 1602, his property, including the family brewery in Schwarzach, Bavaria, was seized by Maximilian I, the Duke of Bavaria and later Prince-Elector of the Holy Roman Empire.

The researchers found that on October 24, 1602, top fermenting yeast was brought from the Schwarzach brewery to the Duke’s Hofbräuhaus brewery in Munich, where the team believes they "mated" to create the new species, S. pastorianus, which has since gone on to dominate the world.

Professor John Morrissey of UCC’s School of Microbiology, a co-author of the research, said every one of the 150 billion litres of beer brewed today can be traced back to that strain. 

“We often think historical events are almost pre-programmed, but this is an amazing example of how chance events which culminated in a new yeast species changed the world of beer," he said. 

"Understanding how this hybridisation started, and evolved, could help us design new strains."