Effect of chemicals on production, composition and antioxidant activity of polysaccharides of Inonotus obliquus.

Polysaccharides are important secondary metabolites from the medicinal mushroom Inonotus obliquus. Various fatty acids, surfactants and organic solvents as cell membrane-reorganizing chemicals were investigated for their stimulatory effects on the growth of fungal mycelium and production of exopolysaccharides (EPS) and endopolysaccharides (IPS) by submerged fermentation of I. obliquus. After evaluation of 14 chemicals, oleic acid, Tween 80, and TritonX-100 were chosen for optimization of addition concentration and addition time. Among the three chemicals, 0.1% (v/v) Tween 80 gave maximum production of mycelial biomass, EPS, IPS1, and IPS2 with a increase of 16.6, 81.6, 37.7 and 18.1%, respectively, when supplemented at the early growth phase (24h after inoculation). These EPS, IPS1, and IPS2 had significantly (p<0.05) stronger scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals than those from the control medium. IPS1 from Tween 80-containing medium was the most effective antioxidant, with an estimated IC50 value of 0.74mg/mL. This might be attributed to that the EPS and IPS from the Tween 80-containing medium had significantly (p<0.05) higher content of sugar and glucose among the six monosaccharide compositions than those from the control. The simultaneously enhanced accumulation of bioactive EPS and IPS of cultured I. obliquus supplemented with Tween 80 was evident.