It’s happened before: About 500 years ago, Saccharomyces cerevisiae, the yeast responsible for wine, bread, and ales, accidentally made a huge biological change. S. cerevisiae hybridized with its distant cousin, Saccharomyces eubayanus, a species that inhabits tree galls in nature, and this combination of the two—which are as evolutionarily diverse as humans and chickens—granted us the yeast that permits the cold-temperature fermentation necessary for lager beer.
Thanks to this happy, less than one-in-a-billion occurrence, we now have a booming $250 billion global lager industry—which means finding the next big strain could make big bucks, and not just in the beer market: Wine, biofuels, and other yeast products could be changed, too.
New strains under investigation
Scientists are all ready working to do this, with the aid of a new method for making interspecies yeast hybrids. They’ve already created new strains of yeast that are being investigated for use in these various industries.
“We can achieve hybrids at rates of one in a thousand cells,” said William Alexander, a University of Wisconsin-Madison postdoctoral research associate and the lead author, in a statement. “It is much more efficient than nature.”
According to a paper published in Fungal Genetics and Biology, the technique involves using plasmids—rings of DNA that have been taken from bacteria. Plasmids allow bacteria to share DNA between each other (via a process called transformation), thereby allowing them to quickly share novel traits like antibiotic resistance.
However, what normally would give scientists a headache is now a tool to insert genes into non-bacterial cells. In yeast, plasmids were used to insert DNA that caused the yeast to start producing a protein that allows normally incompatible yeast species to mate. Then, after the hybrids were made, the plasmids were removed—thus facilitating hybridizations while leaving the original DNA unchanged.
“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. “Within a week, you can generate a large number of hybrids of whatever two species you want, creating forms never seen before.”
Endless possibilities
Currently, there are hundreds of identified yeast species, which can be found practically anywhere in the world, meaning the combinations are practically endless. Yeast has long been man’s best friend thanks to its metabolism, which relies on fermentation—the process by which yeast converts sugars to alcohol and carbon dioxide. And it’s not only used in alcohol; yeast also is used to make cheese, yogurt, soy sauce, biofuels, enzymes, and even drugs like human insulin.
In regards to beverages, different strains of yeast mean new flavors, enhanced production, or entirely new products (like an entirely new kind of beer!)—and being able to quickly churn out new yeast species means faster growth in all these areas. Already, one of the new strains created in the study is being tested in beer by the UW-Madison Department of Food Science.
This technique may help the beer industry overcome its creative bottleneck, since many current industrial yeast strains are sterile.
“If you have a favorite ale strain, for example, you should easily be able to hybridize it with a wild strain using this method,” explained Hittinger. “There is a lot of potential out there for new flavors and combinations.”
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