Abstract: In order to optimize the extraction and decolorization processes of scleroglucan and evaluate the antioxidant properties of the product so as to improve the yield and quality of scleroglucan, the alcohol-precipitation method was adopted for scleroglucan extraction. The main results were as follows: the content of scleroglucan was 0.165 mg/mL by phenol-sulfuric acid method, and the polysaccharide retention rate was 96.66% when the volume ratio of fermentation broth to anhydrous ethanol was 1∶2 by alcohol precipitation method. Small granular activated carbon, macroporous resin D101 and macroporous resin S8 were used to screen the decolorization conditions. Single factor tests were carried out from five aspects: decolorization temperature, decolorization time, pH and the type of decolorizing material and additive amount of decoloring material. The optimal conditions for small granular activated carbon decolorization were 40 ℃, 50 min and the amount of pH 4.0 and additive amount of 2.0%. The optimal conditions for macroporous resin D101 are 30 ℃, 30 min, pH 3 and 13.33%. The best condition for macroporous resin S8 is 30 ℃, 60 min, pH 4 and 30% addition. In the study of the antioxidant activity of scleroglucan, when the concentration of scleroglucan was 6 mg/mL, the absorbance value was about 0.329 at 700 nm; when the concentration of scleroglucan was 3 mg/mL, the scavenging rates of DPPH and superoxide anion radical were 96.17% and 35.76%, respectively. The scavenging ability of scleroglucan to hydroxyl free radical was little related to the concentration, and the clearance rate can reach about 99.44%. The results showed that scleroglucan had certain antioxidant capacity in vitro. In addition, the values of 75% oat extract as the control were lower than that of scleroglucan, which indicated that scleroglucan had better antioxidant properties, which provides a theoretical basis for further development and utilization of scleroglucan, and has excellent economic value and application prospects.

Key words: scleroglucan, alcohol precipitation extraction, polysaccharide decolorization, antioxidant activity