Evolution of sourdough microbiota in spontaneous sourdoughs started with different plant materials.

The preparation of sourdough in bakeries may include the use of inocula, e.g. fruits, flowers or rumen cuts to accelerate the process of selection of suitable microorganisms. The aim of this work was to investigate the effect of these inocula on the microbial evolution in sourdoughs. First, the microbiota of nineteen traditional sourdoughs that were initially started with diverse inocula was identified. Second, de novo sourdoughs were started with plant materials and the evolution of sourdough microbiota was investigated by culture, and by high-resolution melting curve quantitative PCR (HRM-qPCR). This study developed a new protocol for HRM-qPCR analysis of yeast microbiota in sourdough, and indicates this independent culture method suitable for characterization of yeasts. Microbiota of traditional sourdoughs were largely independent from the use of inoculum, however, Acetobacter spp. were identified only in sourdoughs started with apple flowers or apple pulp. In de novo sourdoughs started with plant materials, microbiota rapidly stabilized, and were characterized by Lactobacillus sanfranciscensis, Lactobacillus plantarum, Lactobacillus graminis, or Lactobacillus rossiae, and Saccharomyces cerevisiae as dominant species. Competition experiments revealed that the ecological fitness of L. plantarum, L. graminis, and L. rossiae in wheat or rye malt sourdoughs was lower when compared to L. sanfranciscensis, demonstrating that their presence in de novo sourdoughs reflects dispersal limitation. In conclusion, establishment of microbiota in de novo sourdoughs is dispersal limited. This study provides scientific support for the artisanal practice to inoculate de novo sourdoughs with flowers, berries, or related plant material.