Treatment Coded setting levels Real levels Xylanase activity (IU/mL) X1 X2 X1 X2 LEB-AAD5 LEB-AY10 1 -1 -1 55 3.8 0.363 0.613 2 1 -1 75 3.8 0.087 0.850 3 -1 1 55 5.8 0.500 0.780 4 1 1 75 5.8 0.207 1.440 5 -1.41 0 50 4.8 0.523 0.677 6 1.41 0 80 4.8 0.223 1.847 7 0 -1.41 65 3.4 0.043 0.683 8 0 1.41 65 6.2 0.573 1.080 9 0 0 65 4.8 0.823 1.257 10 0 0 65 4.8 0.883 1.173 11 0 0 65 4.8 0.743 1.257 Results represent the mean of three experiments. X1 = T(°C), X2 = pH, code settings are X1 = (temperature – 65)/10, X2 = (pH – 4.8)/1.0.

Table 1: Process variables used in the first CCD, showing the treatment combinations and the mean experimental responses.