Lactic Acid Bacteria and Lemon Peel Powder Enriched Boza, a Fermented Cereal-Based Beverage, Enhances Butyrate Production and Modulates Fecal Microbiota during In Vitro Fermentation.

Grain-based fermented products have gained increasing attention due to their nutritional and health-promoting properties. In this study, various formulations of boza, a traditional fermented cereal-based beverage, with and without lemon peel powder supplementation and probiotic cultures (Levilactobacillus brevis, Limosilactobacillus reuteri) were produced. The samples were tested for microbiological characteristics, pH and titratable acidity, bioactive properties, color parameters, sensory attributes, and their effects on the fecal microbiota. All fortified boza samples exhibited higher lactic acid bacteria and total mesophilic aerobic bacteria counts than control samples, accompanied by lower pH values. Boza supplemented solely with lemon peel powder were higher in total phenolic content, while samples containing lemon peel powder and probiotic cultures (synbiotic boza) exhibited higher antioxidant profile in FRAP assays. Furthermore, synbiotic boza products received higher sensory acceptability scores than controls. In vitro fecal fermentation analysis in which microbial short-chain fatty acids (SCFAs) and microbial compositional changes were assessed using gas chromatography and 16S rRNA sequencing, respectively showed that synbiotic boza products promoted the formation of SCFAs, particularly butyrate, at a level similar to those observed with inulin, a well-established fast-fermenting prebiotic. The increase in butyrate level was accompanied by an enrichment of butyrate- (i.e. Roseburia) and lactate-producing (i.e. Bifidobacterium) taxa. Overall, these findings demonstrate that the incorporation of lemon peel powder and probiotic cultures into boza can yield a synbiotic beverage with preserved technological quality and improved potential to modulate gut microbiota composition and function toward a healthier profile.