Table 2.

Ranges of variables used in experimental design of RSM.

Symbols	Variables	Range	Code level
			-2	-1	0	+1	+2
A	Temperature (°C)	34-42	34	36	38	40	42
B	Tryptone (%)	0.5-1.5	0.5	0.75	1.0	1.25	1.5
C	Inoculum size (ml)	6-14	6	8	10	12	14
D	Incubation time (hrs)	48-64	48	52	56	60	64