Design expert version 8.0.5b

Dry weight and cordycepin production are expressed as means ± SD. An analysis of variance (ANOVA) followed by Tukey's test was applied for multiple comparisons of significant analyses at P < 0.05. Statistical data analyses were performed in SPSS version 17.0 software packet. Design-Expert Version 8.0.5b software package (Stat-Ease Inc., Minneapolis, USA) was used for designing experiments as well as for regression and graphical analysis of the experimental data obtained.

According the single-factor experimental results, a Box-Behnken Design (BBD) with response surface methodology (RSM) was applied to further determine the optimal UAEE conditions. The levels of the three independent variables were confirmed cellulase concentration (X₁, 1.5%–2.5%), ultrasonic time (X₂, 20–30 min) and ultrasonic temperature (X₃, 40–60 °C) related to the response yield of total phenolic content (mg Gallic acid equivalent/g dried weight). The coded and uncoded (actual) levels of the independent variables were given in Table 4. A quadratic polynomial model performed based on experimental data from CCD was explained by the following quadratic equation:
$Y=A_0+{\displaystyle \sum }_{i=1}^3{A}_i{X}_i+{\displaystyle \sum }_{i=1}^3{A}_{ii}{X}_i^2+{\displaystyle \sum }_{i=1}^2{\displaystyle \sum }_{j=i+1}^3{A}_{ij}{X}_i{X}_j$
where Y is response, A₀ is intercept, A_i is coefficient of variable for linear, A_ii is coefficient of variable for quadratic, and A_ii is coefficient of variable for interaction term. X_i and X_j are independent variables.
The experimental data were analyzed using a statistical package, Design-Expert version 8.0.5b, (Stat-Ease Inc., Minneapolis, MN, USA). The adequacy of the established model and statistical significance of the regression coefficients was evaluated by the lack of fit, coefficient of determination (R²), and Fisher test value (F-value) generated from the ANOVA analysis (p < 0.05).