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Beer yeast adapted to life with humans

The domesticated fermentative microorganism has evolved ways to reduce off-flavors and capitalize on a brew tank’s cozy, nutrient-rich environment

by Sarah Everts
September 12, 2016 | A version of this story appeared in Volume 94, Issue 36

Credit: Shutterstock
Beer-making yeast has a cozy life with humans.
Image of glasses of beer and a structure of the off-flavor compound 4-vinylguaiacol.
Credit: Shutterstock
Beer-making yeast has a cozy life with humans.

Long before scientists discovered the existence of microorganisms, humans domesticated yeast, coaxing the organism to make palatable beer in exchange for a reliable supply of food and a stable existence. A comprehensive genetic and phenotypic analysis of 157 Saccharomyces cerevisiae yeast strains used in fermentation industries reveals that beer-making yeasts originate from a few common ancestors that quickly evolved ways to satisfy their brewmasters (Cell 2016, DOI: 10.1016/j.cell.2016.08.020). A team led by Kevin J. Verstrepen and Steven Maere of the Flemish Institute for Biotechnology found that, compared with wild yeast, beer yeast has duplicated genes that help the organism break down maltotriose, a sugar found in beer mash. Many beer yeast strains have also evolved mutations that prevent production of 4-vinylguaiacol, an off-flavor in many beers. Meanwhile, because beer yeast is used continuously from one batch to another, it has lost the ability to reproduce sexually, the researchers found, a skill the organisms would need to survive and to adapt to stressful environments in the wild. By comparison, the team found that wine yeast still retains the ability to reproduce sexually, probably because wine making occurs only in autumn, leaving the yeast to fend for themselves during the rest of the year.


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