Skip to main content
Premium Trial:

Request an Annual Quote

Beer Yeast Genomes Provide Insight on Domestication History, Industrial Use

Westvleteren Trappist ales

NEW YORK (GenomeWeb) – Researchers from the US and Belgium have traced the domestication of industrial yeasts, including those used in brewing beer.

As they reported in Cell today, KU Leuven's Steven Maere and his colleagues sequenced the genomes of 157 industrial strains of Sacchromyces cerevisiae that are used in beer, wine, and bread production, among other uses. Their phylogenetic analysis uncovered five yeast sublineages that have undergone selection for certain traits largely corresponding with how they are used in industry. In addition, the researchers found that the yeast lineages used in brewing exhibited stronger signals of domestication as compared to yeast used in winemaking.

"Four centuries of domestication have left marks in beer yeast genomes associated with traits that are useful in a brewing environment," Maere said in a statement. "In various beer yeast lineages, specific genes have been amplified, deleted, or altered to optimize growth in beer fermenters and beer taste."

He and his colleagues sequenced beer, wine, spirit, sake, bioethanol, bread, and laboratory yeast strains as well as seven strains isolated from spontaneous fermentations to a median 135X coverage.  After assembly, they constructed a maximum-likelihood phylogenetic tree that also drew on a further 24 previously sequenced yeast strains. From this, they found that the industrial yeasts belonged to five main lineages.

These five lineages — dubbed Wine, Beer 1, Beer 2, Asia, and Mixed — largely reflect how those strains are used, as wine yeasts cluster in the Wine lineage and sake yeasts in the Asia lineage. Most beer lineages fell into either the Beer 1 or the Beer 2 lineage — those lineages, the researchers noted, are only distantly related. The mixed lineage included atypical beer and bread strains, while spirit yeasts were found throughout the various lineages.

The researchers further traced the last common ancestor of the yeasts in the Beer 1 lineage to between 1573 AD and 1604 AD and of those in the Beer 2 lineage to between 1645 AD and 1671 AD, all before the discovery of microbes.

There was also, Maere and his colleagues reported, some geographical influences on the lineages. For instance, they uncovered three subpopulations within the Beer 1 lineage that represented yeasts from Belgium and Germany, Britain, and the US. These subpopulations harbored a high degree of nucleotide diversity — higher than that of the Wine lineage — suggesting to the researchers that the split wasn't a recent occurrence.

Beer yeast also exhibited signs of domestication, such as a loss of survival skills and the ability to reproduce sexually. Yeast from the Beer 1 lineages grew poorly under stress conditions, the investigators found, and some 44 percent of the Beer 1 population is oligate asexual, a trait not present in wild strains, which can reproduce sexually or asexually.

By contrast, Wine lineage strains did well in stressed conditions, likely because they aren't in constant use and have to survive outside the winemaking process.

Maere and his colleagues also noted that beer yeasts are better able to metabolize the sugar maltotriose, which is found in the beer medium. They linked this ability to the presence of the AGT1 allele of the sugar transporter MAL11. This allele is present in the Beer 1 lineage as well as in a few strains from the Mixed lineage, but the MAL1 locus and MAL11 gene are absent from the Wine lineage.

At the same time, many of the industrial yeast strains have lost the ability to produce 4-VG, which gives off a spicy, clove-like flavor, while wild strains have retained it. "As far as we know, there's no selective advantage in suppressing the production of 4-VG," Kevin Verstrepen from the University of Leuven said in a statement. "It must have been the brewers saying, 'This tastes good, we're going to reuse it.'"

Interestingly, he and his colleagues noted that yeast strains used to make German Hefeweizen beers — which have a smoky, spicy aroma — have retained the ability to produce 4-VG.

Mapping the genomic structure of yeast, the researchers added, could help breeding efforts to develop new yeast stains to enhance certain flavors or aromas.