Production Optimization, Molecular Characterization and Biological Activities of Exopolysaccharides from Xylaria nigripes.

The optimal culture conditions of exopolysaccharides (EPS) production in sub-merged culture medium by Xylaria nigl4pes were determined using orthogonal matrix method. The optimal medium (per liter) EPS was 60.0 g L-1 maltose, 1.0 g L-1 peptone 5 mmol L-1 KH2PO4, and initial pH 7.0 at 28 °C. In the optimal culture medium, the maximum EPS production was 11.967 g L-1 in shake flask. Two groups of EPSs (designated as Fr-I and Fr-II) were obtained from the culture filtrates by size exclusion chromatography (SEC), and their molecular characteristics were examined by a multiangle laser-light scattering (MALLS) and refractive index (RI) detector system. The weight-average molar masses of Fr-I and Fr-II of EPS were determined to be 6.327 x 104 and 1.478 x 104 g mo1-1, respectively. The SEC/MALLS analysis revealed that the molecular formation of Fr-I is of nearly globular shape. Furthermore, the experiments in vitro indicated that X. nigripes EPS exhibited high antioxidative effects though its antitumour activity was limited. [ABSTRACT FROM AUTHOR]