Hyperproduction of exopolysaccharides by submerged mycelial culture of Ganoderma lucidum using a solid seed grown in fine-powder of wheat bran and in vitro evaluation of the antioxidant activity of the exopolysaccharides produced.

To facilitate Ganoderma lucidum submerged culture and obtain high productivity, a fine powder of wheat bran was used to grow the fungus for solid-state fermentation and as solid seed for its submerged cultures. The results indicated that the optimal inoculum size was low, being 0.75 g in 250 mL-sized flasks containing 80 mL medium. The maximal exopolysaccharide concentration and biomass produced was 0.74 and 14.71 g/L, respectively, which is considerably higher than that obtained with the commonly used mycelial pellet liquid seed (0.47 and 8.56 g/L, respectively). The EPS and biomass productivity of the solid seed cultures decreased only slightly, even after a 6-month storage period. EPS produced showed higher antioxidant activity compared with that produced in the liquid seed cultures. The developed solid seed can serve as a ready-to-use inoculum for long-term use in G. lucidum submerged culture for the hyperproduction of highly bioactive EPS and biomass.