A mannogalactoglucan from steam-exploded Hericium erinaceus: structural elucidation, digestion resistance and gut microbiota-modulating prebiotic activity.

Steam explosion (SE) pretreatment effectively enhanced the extraction yield and bioactivity of polysaccharides from Hericium erinaceus (H. erinaceus), demonstrating notable therapeutic potential. In this study, a polysaccharide fraction (Q60E) was isolated from SE-treated H. erinaceus. Structural analysis revealed that Q60E (M w , 8.89 × 104 g/mol) was a mannogalactoglucan, featuring a backbone of →3)-α-Manp-(1→, →6)-β-Glcp-(1→, →3,6)-β-Glcp-(1→, →3)-α-Glcp-(1 → and →4,6)-β-Galp-(1 → linkages with side chains of →4)-α-Glcp-(1 → and terminal β-Glcp-(1 → residues. Based on the shape factor ρ (1.71) and the Mark-Houwink-Sakurada parameter (exponent α, 0.51), Q60E adopted a random coil conformation in aqueous solution. In vitro fermentation studies demonstrated that Q60E modulated gut microbiota by promoting beneficial genera (Lactobacillus, Lachnospira and Bifidobacterium) while suppressing pathogenic Fusobacterium. Furthermore, Q60E fermentation additionally enhanced the acetic acid and total SCFAs production, underscoring its prebiotic capacity. These findings highlight the potential of the mannogalactoglucan from SE-pretreated H. erinaceus as effective prebiotics for gut health.