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    The Evolution of Beer Yeast

    For thousands of years, humans have harnessed the natural metabolic activity of yeast, a microorganism that breaks down sugars into alcohol, to make beer and wine. A paper published last week (September 8) in Cell reveals how, over hundreds of years, humans transformed the wild fungus Saccharomyces cerevisiae into a variety of strains tuned for particular tipples.
    A team of scientists from University of Leuven, Vlaams Instituut voor Biotechnologie (VIB), and Ghent University in Belgium sequenced the genomes of 157 strains of Saccharomyces cerevisiae yeasts that are used to make beer, wine, bread, and other products on commercial scales. The team found five sublineages, with distinct phenotypes from wild yeasts, that have been cultivated for human use. Geographic boundaries further divided each category: in one grouping of beer yeast, for example, the strains from Belgium and Germany were closely related, but separate from those in the UK and US.

    This graph represents the history and domestication of yeast used for making beer and other types of alcohol are revealed through genomic and phenotypic analyses. Credit: Gallone and Steensels et al./Cell 2016

    The researchers also dated the earliest cultivated yeast strains to the 1500s, which is likely a consequence of beer production in Europe moving from pubs into monasteries, where brewers began to retain yeast from one batch of beer to the next, according to Nature News. As these early brewers fine-tuned their recipes, they also selected for favorable yeast strains. Domesticated yeasts have a greater capacity to metabolize sugar, fewer distasteful byproducts, and weaker reproductive abilities, compared to their wild-type cousins.
    “The flavor of the beer we drink largely depends on yeast," Kevin Verstrepen of the University of Leuven and VIB explained to “We're drinking the best beers now because ancient brewers were smart enough to start breeding yeast before they knew what they were doing. It was really an art.”