Table 1.

Coded and decoded values for each variables of central composite design (CCD).

Variables	Coded levels of the experimental variables
	−α	−1	0	+1	+α
Temperature (°C)	45	50	55	60	65
pH	4.0	4.25	4.5	4.75	5.0
Enzyme loading (mL)	0.2	0.4	0.6	0.8	1.0
Substrate loading (g)	0.1	0.2	0.3	0.4	0.5