Promotion of fungal growth and underlying physiochemical changes of polysaccharides in Rigidoporus ulmarius, an edible Basidiomycete mushroom

Rigidoporus ulmarius is an edible fungus used for medicinal purposes. The aim of this research was to investigate the effects of different carbon sources and initial pH values of the medium on mycelial growth, and analyze underlying changes in polysaccharides. The maximum mycelial growth of 20.91 g/l was obtained at 20 g/l potato dextrose broth (PDB) with 20 g/l glucose, pH 4.5. Increasing sucrose- or glucose concentration from 5 to 20 g/l in the media enhanced mycelia synthesizing polysaccharides in the molecular-weight range (>600 kDa), and inhibited that of polysaccharide in molecular-weight range (5-20 kDa). When the initial pH of the medium increased from 4.5 to 6.5, mycelia synthesized polysaccharides in high-molecular-weight (>600 kDa) decreased and that of low-molecular weight (8-11 kDa) polysaccharides increased. Feeding with sucrose or glucose resulted in a direct dosage effect to the fucose, glucose, and mannose components of the polysaccharides.