Diversity of indigenous bacteria in fermented dough with Saccharomyces cerevisiae Y10 and Torulaspora delbrueckii Y22

There is a great diversity of indigenous microorganisms in flour, the number of which increased greatly during long-term dough fermentation, affecting dough fermentation and product quality. In this study, the diversity of indigenous bacteria in fermented dough inoculated with single Saccharomyces cerevisiae Y10 strain, Torulaspora delbrueckii Y22 strain and their co-culture was revealed by Illumina MiSeq sequencing. Compared with the dough without yeast inoculation, the bacteria diversity in yeast fermented dough was lower after 12 h fermentation. However, the abundance of lactic acid bacteria (LAB) in the dough inoculated with yeast was higher than that in dough without any yeast inoculated. Similar community structures of bacteria were found in doughs inoculated with different yeast, but their abundance were different. The abundance of the genus Clostridium in doughs inoculated with single S. cerevisiae Y10 was lower than non-inoculated dough, doughs inoculated with T. delbrueckii Y22 and co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 at the same fermentation stage. In comparison with the dough without yeast inoculation, the presence of T. delbrueckii Y22 and the co-culture of S. cerevisiae Y10 and T. delbrueckii Y22 decreased the relative abundance of Staphylococcus, Cronobacter and Enterobacter in fermented dough. Furthermore, the relative abundance of Komagataeibacter increased in the presence of co-culture of S. cerevisiae Y10 and T. delbrueckii Y22. The results of this study suggested that the diversity of indigenous bacteria during dough fermentation was greatly influenced by the starter strain.