Dynamic structural evolution and in vitro colonic fermentability of modified Dictyophora indusiata soluble dietary fibers

Steam explosion reduced crystallinity, enriching primary degraders and butyrate. • Cellulase hydrolysis reorganized hydrogen bonds, enriching Bifidobacterium. • Both structural modifications competitively excluded Escherichia-Shigella. • Dynamic structural evolution of SDFs dictates specific prebiotic mechanisms. Understanding the degradation behavior of soluble dietary fibers (SDFs) during gastrointestinal transit is essential for elucidating their prebiotic mechanisms and optimizing their application as functional food ingredients. This study investigated the dynamic structural evolution and in vitro colonic fermentability of Dictyophora indusiata SDFs modified by steam explosion (S-SDF) and cellulase hydrolysis (E-SDF). After surviving simulated upper gastrointestinal digestion, the modified SDFs exhibited distinct structural degradation kinetics during fecal fermentation. Thermomechanical disruption facilitated the progressive decrystallization of S-SDF (reducing crystallinity to 1.9% at 48 h). This time-dependent structural transition was accompanied by an increase in the relative abundance of Bacteroidota to 18.38% and a butyric acid concentration of 1251.2 μg/mL. Conversely, cellulase modification reorganized intermolecular hydrogen-bond networks, which accelerated the early-stage structural breakdown of E-SDF (generating 1630.78 μg/mL of total SCFAs at 24 h) and was associated with higher relative abundances of the [ Eubacterium ] ventriosum group alongside Bifidobacterium . Furthermore, the modified SDF groups exhibited lower relative abundances of Escherichia–Shigella under fermentation conditions characterized by greater SCFA accumulation and lower pH. These findings elucidate how specific processing methods modulate the dynamic degradation trajectories of SDFs in the gut, providing a mechanistic basis for developing tailored functional ingredients from traditional edible fungi. Download: Download high-res image (339KB) Download: Download full-size image