Polysaccharide F2 from <i>Grifola frondosa</i> depicts an excellent prebiotic effect against hyperglycaemia by modulating gut microbiota associated with short-chain fatty acids and bile salt hydrolase

Abstract Grifola frondosa is an edible and medicinal fungus with various biological activities. Previously, we reported that G. frondosa polysaccharide F2 improved insulin resistance in diabetic rats. In this study, our aim was to identify its prebiotic function. Simulated digestion and faecal bacteria fermentation of F2 in vitro were performed to investigate its digestion and fermentation characteristic. The effects of F2 on intestinal microbiota were studied by 16S rDNA sequencing and bioinformatics analysis. Results showed that F2 was not digested in saliva but was minorly degraded in the stomach and intestine. 16S rDNA sequencing results showed that the hypoglycaemic mechanism of F2 may be associated with enhancement of short-chain fatty acids (SCFAs)-producing bacteria (Enterococcus spp.) and bile salt hydrolase-producing bacteria (Bacteroides spp. and Enterococcus spp.), acceleration the bile acids metabolism and SCFAs production. Data suggested that F2 could be utilised by intestinal bacteria to produce hypoglycaemic components, which was a promising prebiotic.