Lager yeast traced to Patagonia

Posted by Emma Woollacott

It's not widely known - well, none of us knew, anyway - that the yeast used to make lager beer is a hybrid of real ale yeast and another species that's about as distant from it genetically as a human is from a chicken.

And, until now, nobody knew where that second yeast came from.

"People have been hunting for this thing for decades," explains Chris Todd Hittinger, one of a team of scientists at Colorado University.

With lager brewing having begun in Bavaria in the fifteenth century, the scientists reckoned the best place to start was a tour of the Bierkellers of Europe - but several hangovers and some liver damage later, they were still out of luck.

"It was fun trying to track down the mystery yeast," says a hiccuping Mark Johnston of the University's School of Medicine.

In the end - possibly due to a drunken mix-up with planes - the team found the elusive yeast in the southern beech forests of Patagonia. It was hustled off to the University of Colorado School of Medicine where the scientists named it Saccharomyces eubayanus - rather bravely; I wouldn't like to have to pronounce that after I'd had a few.

It likes the cold, as the missing lager yeast had been presumed to do, and its DNA sequence looks like that of the unidentified component of the lager yeast genome.

The yeast seems to have changed a little since its transatlantic trip. The Colorado team identified genetic mutations which likely took place in a brewing environment. These refined the lager yeast’s ability to metabolize sugar and malt and to produce sulfites, allowing it to produce the nectar we all know and love today.

So how did yeast get from South America to the caves and monasteries of Bavaria where lager beer was born? The team doesn't know, but has a rather delightful suggestion - that it could have hitched its way on an early sailing ship in the stomach of a fruit fly.

Put you off? No, me neither. Cheers!