2.7. Response surface experimental design176 Based on the results of the single factor tests, a series of experiments were conducted using the177 response surface methodology (RSM) to optimize the hydrolysis conditions. The non-coded178 values of four independent variables by Central Composite (Uniform Precision) Rotatable Design179 are described in Table 1 and used to determine the response pattern and establish a model. The180 four variables were enzyme activity (X1), hydrolysis pH (X2), hydrolysis temperature (X3), and181 hydrolysis time (X4), with 5 levels of each variable. The dependent variables were concentrations182 of glutamine acid (Y1, CGA) and aspartic acid (Y2, CAA)