Preparation and Characterization of Polysaccharides From Grifola frondosa and Their Human Intestinal Flora-modulating Effect.

A novel and efficient hydrogen peroxide/ascorbic acid-assisted extraction method for the preparation of Grifola frondosa polysaccharide (GFP) was developed, and two GFP fractions (GFP-H and GFP-L) with different molecular weights (Mws) were obtained by separation with ultrafiltration. Both high Mw component (GFP-H, Mw 396.4 kDa) and low Mw component (GFP-L, Mw 12.5 kDa) are possibly mainly comprised of →4)-β-Glcp-(1→, →6)-α-Glcp-(1→, →6)-α-Galp-(1→, α-T-Glcp, →3,6)-α-Manp-(1→, and β-D-GlcpA-(1→ units. The physicochemical properties of GFPs, such as surface morphology, rheological properties, and thermal stability, were also analyzed. Their modulatory effects on human gut microbiota were evaluated using a simulated human intestinal fermentation model in vitro. The results showed that GFPs could be degraded by intestinal microorganisms and promoted the production of short-chain fatty acids such as acetic acid and butyric acid. Compared with GFP-L, GFP-H exhibited a better ability to increase the abundance of beneficial bacteria (e.g., Bifidobacterium, Megasphaera, and Lactobacillus) and reduce the abundance of harmful bacteria (e.g., Escherichia/Shigella, and Lachnoclostridium). This work revealed that Mw of GFP had a significant impact on the human gut microbiota-regulating effect. This study provided valuable information about the relationship between the structure of GFPs and their regulatory effect on intestinal flora.