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Table 2 Central composite experimental design matrix of the three investigated variables, with the total measured H 2 production for each of the experimental runs

From: Revealing the factors influencing a fermentative biohydrogen production process using industrial wastewater as fermentation substrate

Run number

Variable

Response

X1

X 2

X3

Total hydrogen production mean (mL)

1

-1

-1

-1

8.66

2

-1

-1

1

9.62

3

-1

1

-1

22.34

4

-1

1

1

25.23

5

1

-1

-1

8.28

6

1

-1

1

8.35

7

1

1

-1

14.67

8

1

1

1

11.92

9

-1.28

0

0

17.67

10

1.28

0

0

10.43

11

0

-1.28

0

2.97

12

0

1.28

0

27.18

13

0

0

-1.28

14.95

14

0

0

1.28

25.92

15

0

0

0

21.08

16

0

0

0

21.66