Response surface methodology for optimization of polysaccharides extraction by mild alkaline hydrolysis from fruiting body of medicinal mushroom,Ganoderma lucidum

Abstract

Polysaccharides (PLS) is a major source of biological activity and therapeutic use ofmedicinal basidiomycete, Ganoderma lucidum. The aim of this study was to systematically obtain a model of factors that would yield an optimized extraction condition of PLS from fruiting body of G. lucidum, and compared alkaline hydrolysis extraction and aqueous extraction methods in PLS extraction. Independent variables such as alkaline (NaOH)concentration (X1), extraction temperature (X2), and extraction time (X3), were optimized using a 3-factor, 3-level Central Composite Design. The dependent variable was extraction rate (Y1). A mathematical model obtained, Y1 = 3.76 + 0.94 x1 + 0.48 x2 + 0.03 x3 – 0.12 x12+ 0.20 x1x2 - 0.54 x22 - 0.36 x32 (r2 = 0.89), explained the main and quadratic effects, and the interaction of factors that affected the extraction rate. Response surface methodology (RSM) predicted the levels of factors X1, X2, and X3 (1.29 mol/l, 58.55°C and 2.16 h,respectively), for a maximized response of extraction rate. The observed and predicted values of Y1 were in close agreement. Furthermore, the PLS content and the total extract rate from alkaline extraction method were obviously higher than those from the aqueous extraction method. Key words: Medicinal mushroom, Ganoderma lucidum, polysaccharides extraction, response surface methodology, central composite design.