Simulated digestion and fermentation in vitro by human gut microbiota of intra- and extra-cellular polysaccharides from Aspergillus cristatus

Fuzhuan brick tea is characterized in unique "golden flower" of Aspergillus cristatus. However, little information is available for infra- and extra-cellular polysaccharides from A. cristatus (IPS and EPS, respectively). Therefore, simulated digestion and fermentation in vitro were carried out to investigate whether IPS and EPS could be broken down in digestive system. Furthermore, their interactions with gut microbiota were investigated. It was found that IPS and EPS were utilized by gut microbiota to metabolize into short-chain fatty acids (SCFAs). The contents of total acids (SCFAs and lactic acid) in IPS and EPS groups increased to 39.30 +/- 0.66 and 45.18 +/- 1.68 mmol/L, respectively. IPS and EPS could obviously modulate the composition of gut microbiota. Thereinto, IPS could maintain the growth of OTU26 and OTU69 (Prevotella) and increase the relative levels of OTU30, OTU31, OTU35 and OTU56 (Bacteroides), whereas, EPS could maintain the growth of OTU26 and OTU48 (Prevotella) and increase the relative levels of OTU35, OTU56 and OTU63 (Bacteroides). OTU26, OTU61 and OTU69 (Prevotella) showed significantly positive correlations with propionic acid, OTU48 (Prevotella) and OTU56 (Bacteroides) showed significantly positive correlations with acetic acid. Hence, IPS and EPS could regulate the composition of gut microbiota, thereby promote production of SCFAs.