Hybridization between different types of yeast promoted adaptation to the brewing environment and the emergence of different beer styles, reports a pair of papers published in Nature Ecology & Evolution.
For thousands of years, humans have been using Saccharomyces yeasts to produce a variety of fermented products such as beer and wine. During domestication, humans created many yeast varieties adapted to different industrial environments, which are hybrids that combine unique properties from different parental species.
Kevin Verstrepen and colleagues sequenced 200 yeast genomes used in industrial activities including brewing. They found that a quarter of the yeasts analysed were hybrids of four parental species and suggest that hybridization helped to combine traits that improved the brewing process, such as tolerance to cold and fermentation of sugar. The authors observed lack of genetic diversity in today’s lager yeasts, which can be explained by the cultivation, cold storage and distribution of only a few yeast strains during the late nineteenth century. However, brewers in Belgium have maintained traditional brewing practices, and produce beer with a diverse array of yeast strains to this day.
In a separate study, Chris Hittinger and colleagues analysed genomes of 122 Saccharomyces hybrids. The genomes reveal a complex hybridization history involving wild and industrial strains. The hybrids with Saccharomyces cerevisiae parent lineages could be divided into three domesticated lineages. By contrast, the other three parent lineages were all wild lineages. The authors found that several stout and wheat-beer yeasts share the most ancestry with lager brewing yeasts. Like Verstrepen and colleagues, Hittinger and coauthors identify a route of inheritance of the cold-tolerance trait.
Together, these studies demonstrate how hybridization facilitated adaptation and diversification of yeasts in the brewing environment and provide valuable information for development of other industrially relevant yeast hybrids.
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