Comparative Study of In Vitro Colonic Fermentation Dynamics: Human Gut Microbiota Response to Resistant Starch Derived from Germinated and Extruded Pea Seeds

This study explores the temporal interaction between the multi-scale structural evolution of pea-derived resistant starches (RS) and gut microbiota dynamics using a dynamic in vitro colonic model. RS from germinated (GPRS, RS2) and extruded pea seeds (EPRS, RS3) were isolated and their molecular weight, crystallinity, and morphological transformations were characterized during 24-h fermentation. EPRS featured a porous, low-crystallinity matrix that enabled rapid microbial degradation, leading to an early enrichment of Bacteroidetes through starch utilization systems and propionate-dominant short-chain fatty acids (SCFAs) production. In contrast, GPRS preserved its structural integrity with higher molecular order, promoting gradual colonization by Firmicutes via ABC transporter-mediated oligosaccharide uptake and sustained butyrate production. Interestingly, EPRS exhibited higher total SCFAs production than GPRS during the 8-24 h fermentation period. Enzymatic profiling revealed substrate-dependent strategies: EPRS upregulated amylolytic enzymes (K01187) during initial Bacteroidetes dominance, whereas GPRS activated ABC transporters (K10111-K10112) for oligosaccharide internalization by Firmicutes. These results demonstrate that the structural organization of RS in pea seeds fundamentally governs microbiota-SCFAs interactions during colonic fermentation, with extrusion processing enhancing overall fermentability and germination maintaining the butyrate-producing activity. This mechanistic insight could provide a conceptual framework for the rational design of legume-derived prebiotics with tailored physiological benefits.