Prebiotic potential of oligosaccharides extracted from improved Ugandan varieties of millet, sesame, soybean, and sorghum: enhancing probiotic growth and enteric pathogen inhibition

Functional gastrointestinal disorders like diarrhea continue to affect children under five years in low-income countries. Incorporating health-enhancing bioactive compounds such as prebiotics in diet offers a promising solution. This study investigated prebiotic potential of oligosaccharides extracted from improved varieties of millet (Seremi 2, Naromil 2), sesame (Sesim 2, Sesim 3), soybean (Maksoy 3N, Maksoy 6N), and sorghum (Narosorg 2, Narosorg 4), commonly consumed in Uganda. These were compared to their respective indigenous variety. This study employed standardized methods for optical density measurement, culture preparation, and oligosaccharide extraction to evaluate prebiotic properties. We investigated whether plant-based oligosaccharides could enhance the effectiveness of probiotics, specifically Lactiplantibacillus plantarum (ATCC 14917) and Lacticaseibacillus rhamnosus (ATCC 7469), in antagonizing common enteric pathogens (Salmonella enterica subsp. enterica (ATCC 13076) and Shigella flexneri (ATCC 12022)). Approximately 4-8 log CFU/ml of each probiotic was incubated in 2% w/v oligosaccharide extracts at 37 °C to evaluate the influence of the extracts on their growth, short-chain fatty acid (SCFA) production and antagonistic activity. Maximum cell density, which exceeded the minimum recommended probiotic cell density (6 log CFU/ml), was achieved during 24-h incubation period. The probiotics exhibited optimal growth in extracts of Sesim 2, Maksoy 3N, Narosorg 2 and indigenous millet variety resulting in a 68-84% increase in cell densities. The concentration of SCFA concentration was significantly higher (p < 0.05) in soybean-based oligosaccharides. Both probiotics antagonized growth of Salmonella and Shigella by more than 40% when cultured on Sesim 2, Maksoy 3N, Narosorg 2 and indigenous millet variety, while maintaining the probiotic cell densities above the minimum recommended level. These varieties show great potential as functional ingredients for developing synbiotic-rich foods to promote gut and public health. However, to evaluate the oligosaccharides prebiotic efficacy, in vitro fermentation using fecal microbiota and in vivo studies are necessary to determine gut microbiota changes and interactions.