In vitro and in vivo gastrointestinal digestion and fermentation of the polysaccharide from Ganoderma atrum

The study was aimed to investigate the digestion and fermentation behaviors of the bioactive polysaccharide from Ganoderma atrum (PSG) in vitro and in vivo. The molecular weight (Mw) of PSG steadily decreased from 198.0 ± 0.3 to 147.1 ± 0.3 kDa and no free monosaccharides generated throughout simulated gastric and intestinal (GSI) digestion in vitro. The fermentation of PSG by human fecal microbiota was determined by change of pH and production of short-chain fatty acids (SCFAs). The pH in fecal inoculums declined, and the concentrations of total SCFAs, acetic, propionic and butyric acids all significantly improved during fermentation in vitro. In addition, mice were taken PSG orally at doses of 50, 100, 200 mg/kg body weight for 30 days, respectively. After PSG administration, the concentrations of SCFAs increased. Meanwhile, fecal pH continually declined as oral time increased. Combining these findings both in vitro and in vivo, our results showed that the Mw of PSG decreased and no free monosaccharide was produced in GSI digestion and PSG promoted the production of SCFAs and the decline of pH in the large intestinal fermentation, which may provide information that PSG was not entirely digested in GSI digestion and was mainly degraded in the large intestine.