Mechanistic Investigation of the Prebiotic Activity of Selected Nigerian Indigenous Resistant Starches on Human Gut Microbiome Composition and Metabolic Function

The human gut microbiome is increasingly recognised as a central mediator of metabolic health, immune function, and disease risk. Dietary resistant starches function as prebiotics by selectively stimulating beneficial gut microbial taxa, yet the prebiotic activity of resistant starches derived from indigenous Nigerian food sources has not been mechanistically investigated. This study conducted a mechanistic investigation of the prebiotic activity of resistant starch preparations from four Nigerian indigenous food sources: unripe plantain, tiger nut, water yam, and African breadfruit (Treculia africana), on human gut microbiome composition and short-chain fatty acid production. Resistant starch was isolated and characterised from each food source. In vitro fermentation using batch culture simulations with human faecal inoculum from healthy Nigerian adults (n equals 20) was conducted, with commercial inulin as a positive control. Microbiome composition was characterised by 16S rRNA gene amplicon sequencing (Illumina MiSeq, V3-V4 region) at 0, 6, 12, 24, and 48-hour fermentation timepoints. Short-chain fatty acid production was quantified by gas chromatography. Results demonstrated that unripe plantain resistant starch produced the greatest increase in Bifidobacterium and Lactobacillus relative abundance (15.4 percent and 8.2 percent increase respectively), accompanied by the highest butyrate production (18.6 mM at 24 hours). Tiger nut resistant starch showed distinct bifidogenic activity. All four substrates significantly reduced the Firmicutes:Bacteroidetes ratio compared to non-fermented controls. The study identifies indigenous Nigerian resistant starches as potent prebiotic substrates with differential microbial targeting properties. Keywords: prebiotic, resistant starch, gut microbiome, short-chain fatty acids, indigenous foods.