Development of nutritionally enhanced sourdough bread through Tritordeum bran incorporation and assessment in an in vitro gut simulation

• First study on Tritordeum –bran sourdough breadmaking using defined starters. • Fermentation improved bread nutrition, reducing phytic acid and glycemic index. • Sourdough bread with bran was nutritionally superior to baker’s yeast bread. • SHIME Ⓡ showed bran sourdough bread supported butyrate production in the colon. This study for the first time investigated how Tritordeum bran incorporation and starter-assisted sourdough fermentation influence bread nutritional features and gut microbiota, using a defined starter composed of Lactiplantibacillus plantarum LM108.5, Pediococcus pentosaceus TLD10–13, Latilactobacillus curvatus TLD10–17, and Saccharomyces cerevisiae TYD10–5. The bran-based sourdough bread (BSD-B3) showed higher total phenolic compounds (1185 mg GAE/kg), DPPH radical scavenging activity (10.83 mM BHT/100 g), β-glucans (0.39 %), arabinoxylans (3.22 %), and total free amino acids (1758 mg/kg), together with a reduced predicted glycemic index (8.83 %) and improved in vitro protein digestibility (up to 77.2 %) compared to the control (baker’s yeast bread (BYB). Targeted phenolic profiling revealed increased levels of protocatechuic, ferulic, and vanillic acids in BSD-B3, highlighting the contribution of bran and sourdough fermentation to phenolic bioavailability. The impact of Tritordeum sourdough breads with or without bran (TSD-B1 and BSD-B3) on colonic microbiota was evaluated in vitro using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME Ⓡ ). Application of sourdough bread digesta in the SHIME Ⓡ model enhanced short-chain fatty acid production, with BSD-B3 sustaining higher butyrate levels, while TSD-B1 and BYB favored acetate- and propionate-linked bifidogenic activity. Amplicon sequencing (16S rRNA gene) indicated that these metabolic shifts were accompanied by distinct changes in microbial composition and diversity. Our findings suggest that sourdough fermentation, particularly when combined with Tritordeum bran incorporation, produced nutritionally superior bread that selectively alters the gut microbiota.