Purification, Composition Analysis, and Antioxidant Activity of Exopolysaccharides from Mycelial Culture of Paecilomyces cicadae (Miq.) Samson (Ascomycetes)

The biomass growth and exopolysaccharide (EPS) production by a strain of Paecilomyces cicadae (Miq.) Samson ZJ001, which achieved a high concentration of biomass (5.6−6 g/L at day 4), was studied. The crude EPS (containing 68.9% sugar and about 26.2% protein) was fractionated by DEAE-52 column chromatography and puri fied by Sephadex G-100 column chromatography to produce the puri fied EPS (PEPS). Its primary structural features and molecular weight were characterized by Fourier infrared spectrometry (FTIR), gel permeation chromatography (GPC), and gas chromatography (GC). The results indicated that the PEPS was a protein-bound polysaccharide (2.3% protein) composed of rhamnose, arabinose, fucose, xylose, mannose, glucose, and galactose in the molar ratio of 0.63: 13.1:1.30:21.3:46.5:6.0:10.22, with a molecular weight of 167 kDa. The antioxidant activities of the puri fied EPS were evaluated in vitro by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay, the ferric-reducing antioxidant power assay, the superoxide radical assay, and the hydroxyl radical assay. The puri fied EPS was revealed to have strong reductive power (672.3 μmol/L), moderate scavenging activity against DPPH radical (64.1%) and superoxide radicals (58.3%), and potent inhibiting power for hydroxyl radical (92.2%).