Table 3.

Box-Behnken experimental design using four independent variables.

	Substrate concentration (mg/mL)		Inoculation (%)		Initial pH		Enzyme concentrations (mg/g)
Code	X1	Code	X2	Code	X3	Code	X4	Code	Hydrogen Yield (mL/g TS)
1	15	0	30	0	6.0 − 1	100	−1		51
2	15	0	30	0	6.0	−1	200	+1	47
3	15	0	30	0	7.0	+1	200	+1	49
4	15	0	20	−1	6.5	0	100	−1	51
5	25	+1	40	+1	6.5	0	150	0	52
6	15	0	20	−1	6.5	0	200	+1	55
7	5	−1	40	+1	6.5	0	150	0	20
8	15	0	30	0	6.5	0	150	0	58
9	25	+1	30	0	7.0	+1	150	0	46
10	15	0	40	+1	7.0	+1	150	0	42
11	15	0	30	0	6.5	0	150	0	57
12	15	0	20	−1	6.0	−1	150	0	51
13	25	+1	40	+1	6.5	0	100	−1	48
14	5	−1	30	0	6.0	−1	150	0	29
15	25	+1	30	0	6.0	−1	150	0	48
16	5	−1	20	−1	6.5	0	150	0	40
17	5	−1	30	0	6.5	0	100	−1	31
18	15	0	40	+1	6.0	−1	150	0	45
19	5	−1	30	0	6.5	0	200	+1	38
20	15	0	30	0	7.0	+1	100	−1	39
21	15	0	40	+1	6.5	0	100	+1	51
22	15	0	30	0	6.5	0	150	0	58
23	15	0	30	0	6.5	0	150	0	52
24	25	+1	20	−1	6.5	0	150	0	54
25	15	0	20	−1	7.0	+1	150	0	37
26	25	+1	30	0	6.5	0	200	+1	53
27	5	−1	30	0	7.0	+1	150	0	25
28	25	+1	30	0	6.5	0	100	−1	48
29	15	0	30	0	6.5	0	150	0	56