Cordyceps farinosa Cf-GZU06: Mycelium Culture Medium Optimization and Polysaccharide Characterization with Prebiotic Effects

In the present study, medium composition ofCordyceps farinosaCf-GZU06 mycelial fermentation was optimized using response surface methodology. Both intracellular polysaccharides (IPS) and extracellular polysaccharides (EPS) fromC. farinosaCf-GZU06 were obtained and investigated for their structural properties and prebiotic potential. The final medium consisted of 76.170 g/L glucose, 11.056 g/L peptone, 22.201 g/L yeast extract, 0.600 g/L MgSO4·7H2O and 1.400 g/L KH2PO4with the maximum mycelial biomass reaching 44.797 g/L. Structural characteristics showed that EPS and IPS had similar primary structures but different fine structures, especially the aggregate states and microstructures. The primary structures of these two polysaccharides showed limited susceptibility in in vitro digestion with no major changes in their molecular weight (MW) profiles, while the fine structure could be altered during digestion process with less than 17% (w/w) reducing sugar detected. Both EPS and IPS could reshape the fecal microbial composition toward a susceptible balance. The production of short-chain fatty acids (SCFAs) including acetate, propionic and butyric acid was significantly increased, and the total SCFAs was increased to 315.18 mM and 302.81 mM by EPS and IPS respectively compared to inulin (279.06 mM). Microbial metabolic profiles showed that EPS and IPS had totally different impacts on bacterial metabolism. These results suggested that EPS and IPS exhibited a potential prebiotic effect under in vitro conditions, supporting their further evaluation as prebiotic candidates.