In the early 1500s, a brewing revolution was underway in Germany, inadvertently led by a group of brewers who had taken to lagering (lagern being German for 'to store') their beers in caves. By allowing their beers to ferment in this way, the brewers found it gave their brews a crisper taste than ale and everyone at the olde biergarten agreed that it tasted pretty great. The reason for this remained a mystery until the early 1900s however, when the hybrid strain of yeast responsible for giving this newfound beer its distinct flavor profile was at last isolated, allowing for the wholesale production of a drink that we've all come to know and love: the lager.
Today, the 16th century Bavarian brewers' accidental discovery is responsible for the most consumed alcoholic beverage in the world and drives a lager industry worth over $250 billion. Yet the success of lager has not stopped beer scientists from continuing to experiment, although the creation of new beers is a much more controlled process nowadays. Case in point is a team of researchers at the University of Wisconsin, Madison, which has developed a new method for making yeast hybrids in the lab, and have already put one of their four new hybrid species to use in a new beer recipe.
The team's research draws on the wisdom of the old-school German cave brewers who, in their quest to make ale (a drink almost as old as humanity itself) accidentally encouraged the natural hybridization of two species of yeast. Known as Saccharomyces eubayanus, this bottom-fermenting strain of yeast was naturally selected by the cold environment of the caves, unlike the top-fermenting yeast Saccharomyces cervisiae which is used to make ale.
While the UW-Madison team was still making use of Saccharomyces cervisiae to form one half of their hybrids, their yeast hybridization method was slightly more high tech than just putting some barrels in a cave for a few months. The team made use of plasmids, circles of DNA that can be used to manipulate genes in cells, to encourage yeast hybridization by expressing a natural yeast protein that allows two different species to mate. Moreover, the plasmids used to facilitate this process can be removed after the hybridization of the two species is complete, leaving each of their individual genomes unchanged.
"We can achieve hybrids at rates of one in a thousand cells," said William Alexander, a postdoctoral research associate at UW-Madison and the lead author of the paper. "[Our method] is much more efficient than nature."
The work being done by Alexander and his colleagues was detailed in a recent article published in Fungal Genetics and Biology and will have important implications for brewers and others who work with yeast.
According to the team, it will allow brewers to get creative and experiment with flavors that wouldn't have been possible before. At the moment, a problem for brewers looking to mix it up in the flavor department is that most industrial species of yeast are sterile—they cannot produce spores and thus cannot be bred into a new hybrid with other types of yeast. What is more, the team's new method is incredibly efficient, capable of producing new hybrid yeasts in just a week.
"The advantages of the technique are speed, efficiency, and precision," said Chris Todd Hittinger, a UW-Madison professor of genetics and the senior author of the new study. "If you have a favorite ale strain, for example, you should easily be able to hybridize it with a wild strain using this method. Within a week, you can generate a large number of hybrids of whatever two species you want, creating forms never seen before. There is a lot of potential out there for new flavors and combinations."