Antioxidant and Antitumor Activities of β-glucan-rich Exopolysaccharides with Different Molecular Weight from Paenibacillus polymyxa JB115

beta-Glucan isolated from cell wall of fungi not only has low purity and yield, but also causes adverse effects. Consequently, extracellular beta-glucan produced by microorganisms is the focus of this study. beta-Glucan-rich exopolysaccharides (G-EPSs) with different molecular weights from Paenibacillus polymyxa JB115 were prepared by ultrafiltration and spray-drying. The weight-average molecular masses of the G-EPSs, P-SD-1 (spray-dried G-EPSs powder prepared below 100 kDa) and P-SD-2 (spray-dried G-EPSs powder prepared above 100 kDa), were 7.084 x10(4) and 9.235x10(5) g/mol, respectively. beta-Glucan content was 47.38% in P-SD-1 and 73.12% in P-SD-2. The hydroxyl radical- and superoxide radical-scavenging activities of P-SD-2 at 1 mg/mL (39.45 and 87.34%, respectively) were higher than those of P-SD-1 (30.32 and 53.06%, respectively). Maximal nitric oxide (22.24+/-1.34 mu M) was generated in the presence of P-SD-2 (1 mg/mL) and the antitumor activity of P-SD-2 was higher than P-SD-1 in four tumor cell lines (HeLa, Sarcoma 180, A549, and Hep3B cells). Thus, antioxidant and antitumor activities could be enhanced by regulating the molecular weight of G-EPSs. We anticipate that the food and medicinal use of G-EPSs will follow further characterization of this class of exopolysaccharides.