Beer yeasts are dogs, wine yeasts are cats
People have been enjoying the ability of yeasts to produce beer and wine since the dawn of civilization. Researchers from VIB, KU Leuven and Ghent University found that yeasts used for beer and winemaking have been domesticated in the 16th century, around 100 years before the discovery of microbes. Together with a US research team, the Belgian teams analyzed the genomes and fermentation characteristics of more than 150 industrial yeasts used to produce different beers, wines and bread. The results show that the hundreds of beer and wine yeasts available today are the result of brewers and winemakers unconsciously selecting variants that can consume specific sugars, tolerate industrial conditions and produce desired flavors. Fascinatingly, beer yeasts show stronger signs of domestication than wine yeasts, likely because they happily lived in the brewery throughout the year and lost all contact with their feral family members. The results are published in the scientific journal Cell.
In this research project, the lab of yeast expert Kevin Verstrepen (VIB-KU Leuven) and the bioinformatics team of Steven Maere (VIB-UGent) worked side by side.
Yeast breeding avant la lettre
Kevin Verstrepen (VIB-KU Leuven): "The ancestors of the hundreds of different yeasts on the market today have been selected in the 16th century. Ancient brewers, winemakers and bakers often practiced 'backslopping', a technique where a small part of a previous well-fermented dough or brew was kept apart to mix it with a new batch, to make the fermentation process quicker and more consistent. Without realizing what they were doing exactly, these ancient craftsmen were effectively selecting and transferring yeast cultures from one batch to the next, allowing the microbes to continuously grow and adapt to man-made industrial environments."
In order to study a large variety of beers and yeasts, the Belgian team joined forces with White Labs, an American company specialized in selling different yeasts to craft brewers. The scientists found that yeast strains were selected to provide beers with desired industrial characteristics. For example, brewers clearly selected yeasts that do not produce undesirable flavors. And yeasts used for bottle conditioning are more tolerant to high concentrations of alcohol, which is necessary for stronger beers. Steven Maere (VIB-UGent): "The consequences of four centuries of domestication were very clear in the DNA of industrial yeasts. In beer yeasts for instance, specific genes have often been amplified or deleted to optimize growth in beer fermenters and beer taste."
Researchers Brigida Gallone (VIB-KU Leuven-UGent) and Jan Steensels (VIB-KU Leuven) add: "Interestingly, although wine yeasts share their origins with beer yeasts, they show fewer signs of domestication. This is probably because wine yeasts are only used to ferment grape juice once a year, and survive in and around the winery for the rest of the year, where they may interbreed with feral yeasts. In that sense, beer yeasts are like dogs, completely "tamed" and adapted to their relation with humans, whereas wine yeasts resemble the wilder character of cats."
The new study does not only yield insight in how humans have shaped the evolution and genomes of today's industrial yeasts, but also allows breeding even better yeast variants. The scientists are already using the genome sequences to select hybrids that combine beneficial DNA regions from several existing beer and wine yeasts.
"Mapping out the genome structure of yeasts in food or drinks, allows us to better understand the mechanics and applications of yeasts. As a result, it opens up new possibilities to breed yeasts to enhance flavors, aromas or conservation techniques," Kevin Verstrepen (VIB-KU Leuven) comments.