High-purity soybean insoluble dietary fiber as a functional ingredient: Insights into colonic fermentation characteristics and microbiota-driven short-chain fatty acid production

High-purity soybean insoluble dietary fiber (HPSIDF) was evaluated for its colonic fermentation behavior and microbiota-mediated health potential. In vitro fecal fermentation induced pronounced structural remodeling of HPSIDF, characterized by surface roughening, particle fragmentation, increased porosity, reduced crystallinity, and shifts in functional group signatures. Monosaccharide analysis suggested that galactose and galacturonic acid were preferentially utilized as key carbon sources to support microbial growth. 16S rRNA sequencing further demonstrated that HPSIDF selectively enriched polysaccharide-degrading taxa such as Bacteroidetes and Bacteroides , while suppressing Klebsiella and Escherichia, genera that include opportunistic pathogens. Consistent with these compositional shifts, HPSIDF increased the abundance of short-chain fatty acid (SCFA) producers, including Lactobacillus, Bifidobacterium, Coprococcus, Blautia , and Faecalibacterium , leading to elevated levels of acetate, propionate, and butyrate, with butyrate primarily associated with Roseburia, Eubacterium , and Megasphaera . These responses were more pronounced in normal-weight microbiota than in obese-derived communities. Collectively, the results suggest that HPSIDF undergoes structural remodeling during fermentation, is effectively degraded by gut microbiota, and exerts selective modulatory effects on microbial ecology and SCFA production, highlighting its potential as a functional polysaccharide for metabolic health regulation.