Abstract
The earliest known evidence of leavened bread comes from Egypt and Chinain the second and first millennia BC, although records of unleavened breads andpotential flour production date back tens of thousands of years. In the 19th century, thediscovery of yeast fermentation led to the development of industrial bakeries in parallelwith traditional sourdough bakeries. While strains of Saccharomyces cerevisiae wereselected for and became the primary yeast used in industrial breadmaking, someartisanal bakeries continued to use natural sourdough. The maintenance of these twotypes of bakery practices led to the evolution of two genetically and phenotypicallydistinct clades of Saccharomyces bakery yeast. In addition to S. cerevisiae, other yeastspecies are regularly found in sourdoughs, in particular yeasts of the genusKazachstania. In the sourdough ecosystem, these yeasts interact with each other andwith bacteria in a positive or negative way, depending on the species and strainsinvolved. In both sourdough and yeasted industrial dough, traits of interest includearoma production, efficient maltose utilization, osmotolerance, desiccation resistance,and freeze tolerance. These traits have largely been explored in S. cerevisiae, but thereis abundant diversity in these traits even amongst strains of S. cerevisiae, and in thehandful of yeast species that have been surveyed outside of Saccharomyces. The newinterest in sourdough breadmaking and the societal desire to develop more sustainableand biodiversity-friendly bakeries is now leading bakers and scientists to explore thegenetic and metabolic diversity of other yeast species.