Optimization of ultrasonic extraction of mycelial polysaccharides from Paecilomyces hepiali using response surface methodology and its antioxidant activity

Abstract

Ultrasonic technology was applied to extract mycelial polysaccharides fromPaecilomyces hepiali and the process was optimized by response surface methodology. Antioxidant activity of polysaccharides was also investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (%DPPHsc). Three independent variables were ratio of water to raw material (x1), ultrasonic power (x2) and extraction time (x3). Statistical analysis indicated that x1, x2, x12, x32, x1x2, x1x3and x2x3 had significant effect on the yields. Besides, x2, x12 and x22 shaped the %DPPHsc of polysaccharides significantly. Three dimensional surface plots and contour plots were drawn from the mathematical model. The optimal conditions for yield and %DPPHsc were as follows: condition (1) x1 = 125 mL/g, x2 = 300 W, x3 = 12 min, and condition (2) x1 = 125 mL/g and x2 = 500 W, x3 = 11 min, respectively. Under these conditions, the yield was 9.37%, and %DPPHsc was 45.34%. There existed good agreement between experimental and predicted values. Key words: Ultrasonic extraction, polysaccharides, Paecilomyces hepiali, response surface methodology, antioxidant activity.