Medium optimization, molecular characterization, and bioactivity of exopolysaccharides from Pleurotus eryngii

An optimal medium for exopolysaccharides (EPS) production was obtained through one-factor-at-a-time method and response surface methodology. Under optimal culture medium, the maximum EPS concentration in shake flask was 5.16 g/l. Two groups of EPSs (designated as Fr-I and Fr-II) were obtained from the culture filtrates by size exclusion chromatography/multiangle laser light scattering, and the weight average molar masses (Mw) of Fr-I and Fr-II were determined to be 4.098 × 10⁴and 1.114 × 10⁴ g/mol, respectively. The molecular confirmation of Fr-I was revealed to be a rigid rod form in aqueous solution. Moreover, monosaccharide composition and characteristic groups were investigated by GC and Fourier transform infrared, respectively. Finally, pharmacology experiment in vitro indicated EPS Fr-II of Pleurotus eryngii exhibited higher antioxidant and antitumor abilities than Fr-I, which might be attributed to the different molecular weights and chemical compositions in the EPS fraction.