Domestication of a Wild Polyporus tuberaster and Antioxidant Activity of Its Polysaccharide Extracts

To exploit wild mushroom resources in Tibet, a wild strain from Tibet was isolated, identified as Polyporust tuberaster, and domesticated for fruiting. Its growth characteristics were studied, and the antioxidant activities of the intracellular polysaccharides extracts (IPS) extracted from the mycelium and the extracellular polysaccharides extracts (EPS) from the fermentation broth were compared. The optimum carbon source for mycelial growth is fructose; the optimum nitrogen source is ammonium sulfate; the optimum pH is 5; and the optimum temperature is 20 °C. Both extracellular polysaccharide extracts (EPS) and Intracellular polysaccharide extracts (IPS) exhibited antioxidant capacity. The IC₅₀ values of EPS for scavenging OH·, ABTS·⁺, and DPPH· were 1.357, 0.125, and 0.683 mg/mL, respectively, while those of IPS were 0.595, 0.152, and 3.401 mg/mL. At 5 mg/mL, the FRAP values were 0.1582 (EPS) and 0.1708 (IPS). In cultivation, mycelium fully colonized bags after 32 d at 23 °C in darkness. Primordia formed within 12 d under 95% humidity with scattered light, and mature fruiting bodies developed after 24 d at 85-90% humidity and 20-23 °C, yielding an average fresh weight of 41.27 g per bag for the first flush. This study provides a basis for further development of P. tuberaster.