Résumé
Leavened bread can be made using either commercial yeast or sourdough, a mixture of flour and water containing a microbial community of yeast and bacteria. Typically, a single yeast species dominates in each sourdough. Previous studies have described the fungal communities in sourdough, showing that the most commonly found yeast species, apart from Saccharomyces cerevisiae, is Maudiozyma humilis (ex Kazachstania humilis) from Saccharomycetaceae (Arora et.al., 2021; Carbonetto et.al., 2018). However, the genetic and phenotypic diversity of M. humilis is not yet fully characterized. In this study, a collection of 36 strains, mostly isolated from sourdough and coming from different countries, was built. Ploidy analysis revealed that 47% of the strains were triploid and 53% were diploid. Genomic diversity was assessed using whole genome sequences. The average loss of heterozygosity across all genomes is 25%. The SNP data showed that the strains clustered intodifferent groups according to their ploidy level, regardless of their country of origin. Fermentation performance and fitness were evaluated in synthetic liquid sourdough medium using a high-throughput automated robotic system and flow cytometry. Fermentation analysis indicated that triploids had a shorter fermentation latency and a higher maximum CO2 production rate compared to diploids. Further analysis will focus on the genes driving these differences, and the aromatic profile of the strains will also be investigated.