Isolation and Purification of Exopolysaccharide from the Fermentation Broth of Bacillus sp. and Its Antioxidant Effect
一株芽孢杆菌胞外多糖的分离纯化及其抗氧化性测定

Based on the Bacillus sp., isolated from Lop Nur Desert, the technology of separation and purification and the antioxidant effect were studied. After centrifugation and vacuum filtration, the deproteinization of supernatant was operated with Sevag reagent. The crude exopolysaccharide (EPS) was obtained by precipitation with ethanol. The optimum conditions for the isolation were as follow: pH 7.0, temperature 4°C, time 1.5 h, and material to ethanol ratio 1: 4. Dissolved in water, the crude EPS was fractional separated on activated carbon column (1.5 cm × 24 cm), eluted with distilled water, 60% ethanol, 95% ethanol, and the main fraction was collected. Then the EPS was purified on Sephadex G-100 gel column, eluted with NaCl (0.2 mol/L). Fractions (4 mL, each) were also combined according to total sugar by phenol-sulfuric acid method and protein content was determined by Coomassie brilliant blue. The results showed that EPS was relatively homogeneous glycoprotein. The data of antioxidation in vitro showed that the EPS had a high an-tioxidant activity, which could quench hydroxyl radical, superoxide radical and had antilipid peroxidation activity. All of these indicated that EPS was a good natural antioxidant.