Optimization of process parameters of the Pholiota squarrosa extracellular polysaccharide by Box–Behnken statistical design

The quantitative effects of fermentation temperature, fermentation time and inoculum volume on the yield of Pholiota squarrosa extracellular polysaccharide were investigated using response surface methodology (RSM). The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and also analyzed by appropriate statistical methods. RSM analysis showed good correspondence between experimental and predicted values. It was found that three parameters represented significant effect. The coefficient of determination (R2) for the model was 98.5%. Probability value (P < .0001) demonstrated a very high significance for the regression model. By solving the regression equation and also by analyzing the response surface contour plots, the optimal process parameters were determined: fermentation temperature 28.57 °C, fermentation time 7.82 d and inoculum volume 12.57 ml. Under the optimal conditions the corresponding response value predicted for extracellular polysaccharide production was 853.73 μg per milliliter of fermentation liquor, which was confirmed by validation experiments.