Insights into the microbial species diversity and specific making techniques behind Lebanese sourdough breads

The microbial communities of bread-making sourdoughs worldwide have been extensively studied, typically showing one to two dominant yeast species and one to three co-dominant bacterial species. However, the diversity of sourdoughs in the Middle East remains underexplored, as do the factors shaping these microbial communities. The aim of this study was to analyze for the first time the microbial diversity of Lebanese sourdoughs and to test the impact of the different traditional bread-making practices on their microbial composition. A survey and statistical analysis of bread-making practices among 26 Lebanese bakers identified three distinct groups: wheat-flour sourdough, wheat-flour epiphany sourdough, and maize-flour sourdough. Microbial diversity was examined in 50 sourdoughs using metabarcoding with V3-V4 and ITS1 barcodes for bacterial and fungal species, respectively, revealing 141 bacterial species, with Fructilactobacillus sanfranciscensis being the most frequent (34%), and 98 fungal species, with Saccharomyces cerevisiae being the most encountered (20.8%). In parallel, the isolation and characterization of 351 yeast strains confirmed metabarcoding results, providing a valuable Lebanese genetic resource. Weighted UniFrac clustering identified three bacterial and fungal diversity groups, correlating with bread-making practices. Sourdough age, texture, and feeding frequency significantly influenced microbial diversity. Epiphany sourdoughs, which are younger and undergo shorter fermentation, exhibited higher microbial diversity and distinct species composition compared to regular wheat-flour sourdoughs. This suggests that younger sourdoughs may foster a more diverse microbial community than older ones. This study offers the first comprehensive characterization of Lebanese sourdough microbial communities and demonstrates how bread-making practices influence both bacterial and yeast composition.