Table 2.

Optimization of process parameters for l-asparaginase production by Stenotrophomonas maltophilia EMCC2297 variant using Box–Behnken design

Experiment	Temp (°C)	pH	Time (h)	Agitation (rpm)	Square root of l-asparaginase activity (IU/ml/h)		Residual value
					Observed value	Predicted value
1	35	6	33	175	2.5	2.47	0.03
2	40	6	33	175	2.6	2.62	− 0.02
3	35	8	33	175	2.62	2.58	0.04
4	40	8	33	175	2.48	2.5	− 0.02
5	37.5	7	18	150	2.75	2.74	0.01
6	37.5	7	48	150	2.67	2.66	0.01
7	37.5	7	18	200	2.79	2.78	0.01
8	37.5	7	48	200	2.58	2.58	0
9	35	7	33	150	2.62	2.64	− 0.02
10	40	7	33	150	2.55	2.51	0.04
11	35	7	33	200	2.44	2.46	− 0.02
12	40	7	33	200	2.7	2.66	0.04
13	37.5	6	18	175	2.75	2.76	− 0.01
14	37.5	8	18	175	2.71	2.72	− 0.01
15	37.5	6	48	175	2.6	2.58	0.02
16	37.5	8	48	175	2.64	2.61	0.03
17	35	7	18	175	2.69	2.69	0
18	40	7	18	175	2.77	2.77	0
19	35	7	48	175	2.57	2.6	− 0.03
20	40	7	48	175	2.56	2.59	− 0.03
21	37.5	6	33	150	2.6	2.61	− 0.01
22	37.5	8	33	150	2.52	2.55	− 0.03
23	37.5	6	33	200	2.53	2.54	− 0.01
24	37.5	8	33	200	2.58	2.59	− 0.01
25a	37.5	7	33	175	2.71	2.72	− 0.01
26a	37.5	7	33	175	2.73	2.72	0.01
27a	37.5	7	33	175	2.74	2.72	0.02

^aRefers to the experiments that were carried out in triplicates at the mean value of each tested parameter (temperature of incubation, initial pH, time of incubation, rate of agitation)