Bread On Shelves In Bakery in Altamura. Apulia, Italy.

Staff of life: artisanal baker’s yeast has genetic ties to strains found in fruit and other natural sources. Credit: Getty

Genomics

Sourdough starters give rise to a new line of yeast

Artisanal baking practices nourished a strain of yeast that is distinct from industrial microbes.

Humans used yeast to make bread well before the coronavirus pandemic, when stay-at-home orders unleashed a bread-baking frenzy. Now, a survey of yeasts (Saccharomyces cerevisiae) from around the world shows that, over the course of centuries, industrial and artisanal bread making have each led to the evolution of a distinct lineage of baker’s yeast.

Bakers can ferment their dough with industrial cultures of S. cerevisiae or with sourdough, a mix of water and flour fermented by S. cerevisiae and other microbes. To characterize these leavening agents, Delphine Sicard at the University of Montpellier in France and her colleagues analysed 229 S. cerevisiae strains — 31 mass-produced strains sold in stores and used in industrial bakeries and 198 strains from sourdough starters.

Compared with S. cerevisiae used to produce beer and wine, both types of baking yeast produce more CO2, which helps the dough to rise. Industrial strains tend to be more genetically similar to beer-making yeasts, whereas most sourdough strains resemble yeasts found in natural environments, including water and fruit.

Preserving a range of bread-making practices will help to maintain this genetic diversity, the researchers say.