where Y is the predicted value, represented by the enzymatic
activity; β0 is the constant term; βi is the linear coefficient;
βij is the interaction coefficient; βii is the quadratic
coefficient; and xi and xj are the independent variables
in the coded values. The significance of all terms in
the polynomial function was assessed statistically using
the F-value at a probability (p) of 0.05. The model was
then used to generate response surfaces and contour
curves to determine the optimal operating ranges of the
independent variables.