Use of physiological and transcriptome analysis to infer the interactions between Saccharomyces cerevisiae and Lactobacillus sanfranciscensis isolated from Chinese traditional sourdoughs

This study aimed to explore the interaction between Saccharomyces cerevisiae and Lactobacillus sanfranciscensis during sourdough fermentation based on metabolic characteristics and transcriptional changes in pure and mixed cultures. Dough was prepared by using these species either as single cultures, or in combination. The cell counts, acidity and volatile compounds in sourdough samples were determined. The growth of S. cerevisiae and L. sanfranciscensis remained unaffacted in mixed culture. In addition, production of some volatile compounds, mainly associated with S. cerevisiae (ethanol, 2,3-pentanedione, 3-methyl-1-butanol, phenylethyl alcohol and 2-methyl-1-propanol) was negatively affected in mixed culture. On the other hand, S. cerevisiae stimulated the acetic acid production by L. sanfranciscensis, but did not have a significant effect on other metabolic traits of L. sanfranciscensis. The transcriptional profile of S. cerevisiae in pure and mixed cultures was analyzed using RNA sequencing. The results showed a significant effect of co-fermentation on S. cerevisiae carbohydrate and amino acids metabolism. The glycerol synthesis, arginine metabolism and glutamate metabolism increased, while the synthesis of ethanol and acetic acid and glutathione metabolism decreased in mixed culture when compared with results obtained from pure culture of S. cerevisiae.