Yeast hybrids could soon inspire new beer flavours

Beer lovers, rejoice! Your brew could soon come in many flavours, thanks to a new method developed by researchers for making interspecies yeast hybrids in the lab.
The makers of beer, wine and other products that depend on yeasts may have many more strains of the microorganism to work with, researchers said.
"We can achieve hybrids at rates of one in a thousand cells. It is much more efficient than nature," said study lead author William Alexander, a postdoctoral research associate at the University of Wisconsin-Madison.
About 500 years ago, the accidental natural hybridisation of Saccharomyces cerevisiae, the yeast responsible for things like ale, wine and bread, and a distant yeast cousin gave rise to lager beer.

Today, cold-brewed lager is the world's most consumed alcoholic beverage, fuelling an industry with annual sales of more than USD 250 billion, researchers said.
In nature, the odds of a similar hybridisation event are one in a billion.

There are hundreds of known species of yeasts and they occupy almost every ecological niche imaginable worldwide.
They are essential to the process of fermentation, where the microbes convert sugars to alcohol and carbon dioxide.
Yeasts are used widely to not only make beer, wine and bread, but also cider, whiskey, cheese, yogurt, soy sauce and an array of other fermented foods and beverages.

In industry, yeasts are used to produce biofuels and to make enzymes, flavours and pigments and even drugs such as human insulin.
An ability to quickly and efficiently churn out new yeast interspecies hybrids means industries that depend on yeasts will have many more organisms to experiment with to make new flavors, enhance production and produce entirely new products, said senior author Chris Todd Hittinger, a professor at UW-Madison.
For example, the happy marriage of Saccharomyces cerevisiae and its distant cousin Saccharomyces eubayanus, a species that inhabits tree galls in nature, permitted the cold-temperature fermentation that made lager beer possible.

The new yeast hybridisation method uses plasmids, circles of DNA that can be built into an organism to confer a genetic quality.
In the lab, plasmids are routinely used to manipulate genes in cells. Genes in the plasmids facilitate yeast hybridisation by expressing a naturally occurring yeast protein that allows two distinct species of yeasts to mate.
"The advantages of the technique are speed, efficiency, and precision," said Hittinger.
"Within a week, you can generate a large number of hybrids of whatever two species you want, creating forms never seen before," he said.
The new study describes four new hybrids, one of which was made using a strain of Saccharomyces eubayanus discovered near Sheboygan in Wisconsin.

The study was published in the journal Fungal Genetics and Biology.