Optimization and Characterization of an Antioxidant Exopolysaccharide Produced by Cupriavidus pauculus 1490

In the present study, exopolysaccharides (EPS) production by Cupriavidus pauculus 1490 was optimized by response surface methodology. The results showed that sodium gluconate (4.15 g/L), NH4Cl (0.52 g/L), and Na2HPO4·12H2O (0.04 g/L) were the optimal medium components and concentrations. The actual EPS yield of 293.2 m g/L in the optimized medium was in close agreement with the predicted value of 283.35 m g/L. Analysis of fourier transform infrared spectroscopy indicated the EPS contained abundant functional groups, such as –OH, C=O and C–O–C, and all of them were attributed to the characteristics of polysaccharides. Mannose, glucuronic acid, glucose and xylose were detected as the main monosaccharide composition of EPS. Rheological analysis suggested that the rheogram of EPS has similar trend with Xanthan and presented the property of non-Newtonian fluid. Moreover, the addition of NaCl and KCl would partly weaken the shear stress of EPS. Three in vitro assays were conducted to evaluate the antioxidant potential of the EPS. Results demonstrated that the EPS possessed scavenging capacity on hydroxyl radical, DPPH radical and superoxide anion radical in a dose-dependent way. As indicated by above results, the EPS isolated from C. pauculus 1490 might serve as a potential antioxidant agent to be applied in nutraceutical and pharmaceutical industries.