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.

Abbreviation

RSM, Response surface methodology; RCEF, Research Center for Entomogenous Fungi; BBD, Box-Behnken design; DPPH, 2,2-diphenyl-1-picrylhydrazyl