Optimization of Extraction Process of Polysaccharides from Stropharia rugosoannulata in Bo'ai County by Response Surface Method and Evalation of Their Antibacterial and Antioxidant Activity

The ultrasonic-assisted extraction process of polysaccharides from Stropharia rugosoannulata in Bo'ai County and the antibacterial and antioxidant activities were analyzed. On the basis of single factor experiments, with the polysaccharide yield as response value, the ultrasonic-assisted extraction process of polysaccharides from Stropharia rugosoannulata in Bo'ai County was optimized using Box-Behnken experimental design with three factors and three levels. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the polysaccharides extracted from Stropharia rugosoannulata in Bo'ai County were determined using the double dilution method and the plate coating method, respectively. The antioxidant activity was determined using ABTS method and FRAP methods. The results showed that the optimal ultrasonic-assisted extraction conditions were 62 ℃ (ultrasonic temperature), 1:30 g/mL (solid-liquid ratio) and 62 min (ultrasonic time). Under these conditions, the average yield of polysaccharide was 13.25%, which agreed well with the predicted value of 13.35%, the relative error was 0.75%. Among the five common pathogenic bacteria tested, the polysaccharide extract showed the strongest inhibitory effect on Salmonella typhimurium with the minimum inhibitory concentration of 6.25 mg/mL and the minimum bactericidal concentration of 12.5 mg/mL. Meanwhile, the polysaccharide extract showed strong ability to scavenge ABTS+ free radicals and reduce Fe3+, and showed dose-effect relationship within a certain concentration range, although weaker than the positive control (VC) at the same concentration. The results suggested that the regression models were stable and feasible for polysaccharide extraction from Stropharia rugosoannulata in Bo'ai County and the extract had strong antioxidant and antibacterial activities, but its antibacterial effect was selective.