Optimization of a chemically defined medium for mycelial growth and polysaccharide production by medicinal mushroom Phellinus igniarius

A chemically defined medium for mycelial growth and exopolysaccharide (EPS) production by submerged culture of Phellinus igniarius was investigated. The mainly defined medium compositions were optimized by using orthogonal matrix method. The optimal defined medium (per liter) was 40.0 g glucose, 4.0 g. glutamic acid, 4.0 g (NH4)2SO4, and initial pH 6.0. Under the optimal medium, the maximal mycelial biomass and EPS production were 12.33 ± 0.89 and 1.21 ± 0.08 g l−1 at 192 h in shake flask, while the maximal mycelial biomass and EPS production reached 13.86 ± 0.52 and 1.92 ± 0.07 g l−1 at 168 h in 3 l fermenter, respectively. The molecular weights (g mol−1) of four fractions isolated from EPS by gel permeation were about 6.4 × 106, 3.3 × 105, 2.7 × 105 and 2.9 × 103. This study should be widely applied to other secondary metabolites production from higher fungus in a chemically defined medium and quantitative regulation of the metabolic flux in polysaccharide biosynthesis.