Central composite design and experimental results of response surface methodology.

Run	A: IPTG concentration (mg L−1)	B: induced cell density	C: induction temperature (°C)	D: induction culture time (h)	Protein yield (mg mL−1)
					Actual value	Predicted value
1	20	0.2	10	4	0.035 ± 0.003	0.031
2	20	1.2	10	4	0.165 ± 0.012	0.17
3	20	1.2	30	4	0.150 ± 0.002	0.15
4	60	1.2	10	4	0.180 ± 0.005	0.18
5	60	0.2	10	12	0.080 ± 0.004	0.076
6	40	0.7	20	16	0.385 ± 0.004	0.38
7	40	0.7	20	8	0.517 ± 0.009	0.52
8	60	0.2	30	4	0.195 ± 0.011	0.19
9	40	0.7	20	8	0.517 ± 0.009	0.52
10	40	0.7	20	8	0.517 ± 0.009	0.52
11	20	0.2	30	4	0.180 ± 0.005	0.19
12	40	1.7	20	8	0.225 ± 0.005	0.22
13	40	0.7	0	8	0.170 ± 0.005	0.17
14	0	0.7	20	8	0.080 ± 0.004	0.077
15	20	0.2	10	12	0.090 ± 0.009	0.097
16	60	1.2	30	12	0.120 ± 0.005	0.12
17	20	1.2	10	12	0.145 ± 0.007	0.14
18	60	1.2	10	12	0.155 ± 0.004	0.16
19	40	0.7	20	8	0.517 ± 0.009	0.52
20	40	−0.3	20	8	0.009 ± 0.054	0.00575
21	60	0.2	10	4	0.085 ± 0.0124	0.092
22	20	0.2	30	12	0.210 ± 0.030	0.21
23	60	1.2	30	4	0.145 ± 0.002	0.15
24	40	0.7	40	8	0.120 ± 0.009	0.12
25	40	0.7	20	8	0.517 ± 0.009	0.52
26	80	0.7	20	8	0.120 ± 0.005	0.12
27	40	0.7	20	8	0.517 ± 0.009	0.52
28	60	0.2	30	12	0.130 ± 0.007	0.14
29	20	1.2	30	12	0.075 ± 0.002	0.082
30	40	0.7	20	0	0.000 ± 0.000	−0.00325