Application of Box-Behnken design in optimisation for polysaccharides extraction from cultured mycelium of Cordyceps sinensis

A three-level Box-Behnken design, combined with the canonical and ridge analyses, was employed to optimise the process parameters for polysaccharide extraction from cultured mycelium of Cordyceps sinensis, one of the most valued traditional Chinese medicines and health foods. The critical factors selected for the investigation were extraction temperature, duration of time and number of times. The experimental results were fitted with a second-order polynomial equation by a multiple regression analysis and more than 96% of the variation could be predicted by the models. The canonical analysis of surface responses revealed that the three eigenvalues had different signs, indicating a saddle stationary surface. The optimal conditions for extraction of polysaccharides from the cultured mycelium of C. sinensis were determined, using the ridge analysis, as extracting 110 min at 88.9 °C for three times. Under the optimal conditions the corresponding response value predicted for polysaccharide production was 15.85%, which was confirmed by validation experiments.