Preparation and biological activities of an exopolysaccharide produced by Enterobacter cloacae Z0206

A water-soluble extracellular polysaccharide (EPS-1) was isolated from the submerged culture broth of Enterobacter cloacae Z0206 through fermentation, ethanol precipitation, anion-exchange and gel-permeation chromatography. Its structural analysis showed that the average molecular weight of EPS-1 was 23,928 Da, and it was composed of glucose, mannose and galactose with a molar ratio of 6.860:1.180:0.455. It was hypothesized that EPS-1 belongs to the α-type heteropolysaccharide with pyran group. Bioactivity tests in vivo showed that the administration of EPS-1 to cyclophosphamide (CP)-exposed animals resulted in significant increase and recovery of B lymphocyte proliferation, tumor necrosis factor α (TNF-α) production and activities of antioxidant enzymes (superoxide dismutase (SOD) and glutathione peroxidase (GPx)). It is suggested that EPS-1 could provide protection against CP-induced immunosuppression and oxidative damage in mice model, and it may act as a potent immunomodulatory and antioxidant agent.