Study of the dynamics of microbial communities of Russian rye starter cultures of spontaneous fermentation

Background: The study of the spontaneously fermented sourdough microbiome is currently receiving considerable attention worldwide. However, the taxonomic structure of the Russian spontaneously fermented sourdough microbiome remains insufficiently studied using metagenomic methods, despite the important role of the microbiome in ensuring bread quality and safety.

Aim: The aim of the work was to study the dynamics of Russian spontaneous sourdoughs microbial communities during long-term propagation. The objects of the study were eight starter cultures of spontaneous fermentation: four thick rye and four liquid rye starter cultures without brewing.

Methods: Four batches of rye flour of different grades (“wallpaper” and “stripped”) were used to prepare the starter. The composition of microbial communities was determined using high-throughput sequencing of fragments of the 16S rRNA gene.

Results: It was shown that during the sequential refreshing of starter cultures, the proportion of representatives of proteobacteria decreases, while the proportion of Firmicutes increases. The changes in the bacterial community coincided with a decrease in the pH of the starter culture, as well as a significant change in the odor of the starter culture from an unpleasant putrid to a pronounced pleasant odor of the starter culture. The mature starter cultures were dominated by representatives of the Firmicutes type, mainly represented by lactic acid bacteria of the Lactobacillaceae family. It was found that in the process of sequential renewal of starter cultures with water-flour nutrient mixtures, a significant change in the taxonomic structure of the starter microbiome occurs at the level of the Lactobacillaceae family. Namely, the relative abundance of the genera Latilactobacillus, Levilactobacillus, Lactiplantibacillus, Weissella, Pediococcus, Leuconostoc, Lactococcus, Enterococcus, characteristic for young ferments of spontaneous fermentation, decreased, with a simultaneous increase in Fructilactobacillus and Companilactobacillus in dense starter cultures, and Limosilactobacillus and Fructilactobacillus—in liquid starter cultures without brewing. Lactobacilli Fructilactobacillus sanfranciscensis and Companilactobacillus sp. dominated in mature thick rye starter cultures; Limosilactobacillus pontis prevailed in liquid rye starter cultures without welding on stripped flour; L. pontis and F. sanfranciscensis prevailed in wallpaper flour.

Conclusion: As a result of the conducted studies, there were no statistically significant differences in alpha or beta diversity between the starter cultures bred using different grades and batches of flour. It has been shown that the parameters of Russian starter culture management (humidity, temperature), which differ from those accepted abroad, have a decisive influence on the formation of the microbiome of starter cultures of spontaneous fermentation at the level of lactobacillus species.