Computer-controlled simulated gastrointestinal digestion changes in vitro fermentation kinetics, microbial community, and short-chain fatty acid production of fiber-rich ingredients

Dietary fibers (DF) are well-established prebiotics that modulate gut microbiota and enhance host health. Nevertheless, how previous gastric-small intestinal digestion of DF impacts microbiota and metabolites during fermentation remains poorly understood. This study investigated the effects of pre-digestion, using a computer-controlled simulated digestion system (CCSDS) that mimics in vivo gastrointestinal conditions, on the fermentation kinetics, microbial community, and short-chain fatty acid (SCFA) production of six fiber-rich ingredients [sugar beet pulp (SBP), wheat bran (WB), corn DDGS (DDGS), soybean hull (SH), rice bran (RB), and alfalfa meal (AM)], followed an in vitro fecal fermentation was employed. Results showed that simulated digestion reshaped DF fermentation kinetics, with gas production decreased for WB, but increased for SH, SBP, DDGS, and AM (P < 0.05). SCFA profiles diverged significantly, reflected by SBP and DDGS residues increased butyrate production, whereas WB and RB residues reduced acetate and propionate yields (P < 0.05). α-diversity (Sobs, Chao1, and Ace indexes) increased in residues of WB, SBP, and AM (P < 0.05). PCoA analysis confirmed distinct clustering between ingredients and residues (P < 0.01), with residues increasing the abundance of fiber-degrading and SCFA-producing genera (e.g., Prevotellaceae_NK3B31_group in WB residues, Treponema in DDGS residues, Lysinibacillus in RB, SBP, and AM residues). These findings demonstrate that pre-digestion critically modifies DF fermentation and microbiota interactions, providing valuable insights for the selection of DF in diet formulations and enhancing our understanding of their beneficial effects on gut health.