Comparative Insights into Digestion and Gut Microbiota Modulation of Polysaccharides from Ginseng, Ganoderma lucidum, and Dendrobium officinale

Dietary polysaccharides regulate gut microbiota and exhibit diverse prebiotic activity, which is highly dependent on their structural properties. To explore the underlying structure-prebiotic relationship, this study selectively compared the structural characteristics of Ginseng polysaccharide (GP), Ganoderma lucidum polysaccharide (GLP), and Dendrobium officinale polysaccharide (DOP) and investigated their digestive stability and gut microbiota modulation via in vitro simulated digestion and fecal fermentation. Structural analysis revealed distinct differences in molecular weight, monosaccharide composition, and glycosidic linkages among the three polysaccharides. Moreover, GP is partially digested in the upper gastrointestinal tract, while GLP and DOP were resistant to upper-tract digestion. All three polysaccharides differentially modulate gut microbial fermentation, intestinal microbial community structure, and the expression of functional carbohydrate-active enzymes. Specifically, the high glucose content of GP selectively promoted the abundance of genera putatively linked to glucose utilization, including Bacteroides, Bifidobacterium, and Alistipes. GLP preferentially enriched possible genera with galactose-metabolizing ability, such as Blautia, Collinsella, and Megamonas, while DOP selectively enriched microbiota putatively associated with mannose utilization, including Fusicatenibacter and Lachnospiraceae. Taken together, monosaccharide composition is a key structural feature that is closely associated with fermentation efficiency and gut microbial responses to polysaccharides, providing valuable insights for the precision utilization of bioactive polysaccharides.