Solid-state cultivation of Grifola frondosa (Dicks: Fr) S.F. Gray biomass and immunostimulatory effects of fungal intra- and extracellular β-polysaccharides

Grifola frondosa strain GF3, was cultivated on solid-state substrate consisting of milled whole corn plant (Zea mays) and olive press cake supplemented with mineral additives and olive oil. Maintenance of the moisture content in the solid substrate is of crucial importance. Moistures higher than 70% promote growth of G. frondosa mycelium and polysaccharide production. Four fractions of pure extracellular β-d-glucans with total mass 127.2 mg and four fractions of intracellular polysaccharides with total mass 47.2 mg were isolated. Polysaccharides were further separated by ion-exchange, gel and affinity chromatography. Isolated polysaccharide fractions from fungal mycelium proved to induce moderate amounts of TNF-α in PBMC cells in vitro. The extent of TNF-α induction was up to 322 pg mL−1 at a polysaccharide concentration of 200 μg mL−1 for the intracellular fraction. The TNF-α inducing activity is comparable to romurtide, which has been used as a supporting therapy in cancer patients treated with radiotherapy and/or chemotherapy.