Artisanal and farmers bread-making practices differently shape fungal species community composition in French sourdoughs

Abstract

Preserving microbial diversity in food systems is one of the many challenges to be met to achieve food security and quality. Although industrialization led to the selection and spread of specific fermenting microbial strains, there are still ongoing artisanal processes that may allow the conservation of a wider diversity of microbial species. We examined whether the diversity of artisanal practices could lead to an increased level in fungal species diversity for bread making. We used an interdisciplinary participatory research approach including bakers, psycho-sociologists and microbiologists to analyze French bread-making practices and describe fungal communities in naturally fermented sourdough of 27 bakers and 12 farmer bakers. Bread-making practices were classified in two groups: the farmer-like practices group and the artisanal-like practices group. Surprisingly, the well-known bakery yeast, Saccharomyces cerevisiae, was dominant (i.e. with a relative abundance over 50%) in only 24% of sourdoughs while other yeast species of the closely related Kazachstania genus were dominant in 54% of sourdoughs. Bread-making practices were found to drive the distribution of yeast species. The most remarkable difference was the occurrence of Kazachstania humilis in sourdoughs made with artisanal-like practices and the occurrence of Kazachstania bulderi in sourdoughs made with farmer-like practices. Phenotyping of these two species in laboratory sourdough mimicking media revealed phenotypic divergence between sourdough and non-sourdough strains for K. humilis but not for K. bulderi. Overall, our results showed that preserving bread-making practices diversity allows the preservation of a higher taxonomic and phenotypic diversity in microbial communities.