Study of the nutritional changes and evolution of microbiota during sourdough like fermentation of wheat bran

Several studies have emphasized the possibility to enhance nutritional properties of cereal by-products through biotechnological processes. Bran fermentation positively affects the bioavailability of several functional compounds and, in particular, it could increase water-extractable arabinoxylans (WEAX), compounds with positive effects on glucose metabolism and potential prebiotic properties. This study was aimed to increase the amount of bran’s bioactive compounds through sourdough like fermentation process. Wheat bran fermentations were conducted through continuous propagation by back-slopping of fermented bran (10% inoculum) until a stable microbiota was established, reaching high counts of lactic acid bacteria and yeasts (109 and 107 CFU g-1 respectively). After fermentation, levels of soluble fiber increased (+ 30%), WEAX and free ferulic acid were respectively fourfold and tenfold higher than in raw bran, results probably related to microbial xylan-degrading activity, while phytic acid was completely degraded. At each refreshment step, bacterial strains were isolated, clustered, molecularly analysed by Randomly Amplified Polymorphic DNA and identified at the species level by 16S rRNA gene sequencing. Leuconostoc mesenteroides, Lactobacillus brevis, Lactobacillus curvatus, Lactobacillus sakei, Lactobacillus plantarum, Pediococcus pentosaceus and Pichia fermentans were dominating the stable sourdough ecosystem. These strains were characterized by their metabolic and enzymatic activities, such as xylan- and phytate-degrading activities. These preliminary data suggest that fermented bran could be considered as an interesting functional ingredient for nutritional enhancement. The characterization of the bacteria involved in sourdough like fermentation process represents the first step toward selecting starter cultures, according to their functional aspects, in order to conduct “tailored” bran fermentation process aimed at improving its functional and nutritional properties.