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Bioresources and Bioprocessing

Table 2 Independent variables and levels of variation in CCD

From: Application of methanol and sweet potato vine hydrolysate as enhancers of citric acid production by Aspergillus niger

Trial

Variable

CA (g/L)

pH

Temperature (°C)

Inoculum quantity (%)

Fermentation period (d)

SVH (%)

1

4 (−)

35 (+)

12 (−)

7 (+)

12 (+)

2.011

2

6 (+)

35

18 (+)

7

10 (−)

2.485

3

6

25 (−)

18

7

12

2.032

4

5 (0)

30 (0)

15 (0)

6 (0)

13.4 (++)

2.426

5

6

25

12

7

10

2.292

6

5

30

15

6

11 (0)

2.588

7

4

35

18

5 (−)

10

2.216

8

4

35

12

5

12

2.579

9

6

35

12

7

10

2.617

10

4

25

18

7

12

2.284

11

4

35

18

7

10

2.263

12

4

35

18

5

12

2.211

13

6

25

18

5

12

2.852

14

5

30

8 (–)

6

11

2.775

15

5

30

15

6

11

2.803

16

5

42 (++)

15

6

11

2.581

17

6

25

12

7

12

2.466

18

4

25

18

5

12

2.027

19

5

30

15

6

11

2.716

20

5

30

15

6

11

2.685

21

6

25

18

5

10

2.245

22

4

35

18

7

12

2.062

23

5

30

15

6

11

2.788

24

4

25

12

7

12

2.264

25

4

25

12

5

10

2.303

26

5

30

22 (++)

6

11

2.855

27

6

35

18

5

10

2.916

28

6

35

18

5

12

3.682

29

6

25

12

5

10

2.413

30

4

25

12

7

10

2.226

31

6

35

18

7

12

2.591

32

4

25

18

5

10

1.985

33

4

25

12

5

12

2.148

34

6

25

12

5

12

2.583

35

6

35

12

7

12

2.383

36

5

30

15

8.4 (++)

11

2.286

37

2.6 (–)

30

15

6

11

1.981

38

5

18 (–)

15

6

11

2.132

39

6

35

12

5

10

2.851

40

7.4 (++)

30

15

6

11

2.171

41

5

30

15

6

11

2.741

42

5

30

15

6

8.6 (–)

2.733

43

5

30

15

3.6 (–)

11

2.078

44

5

30

15

6

11

2.407

45

5

30

15

6

11

2.593

46

4

25

18

7

10

2.541

47

4

35

12

7

10

2.628

48

4

35

12

5

10

2.619

49

6

35

12

5

12

2.882

50

6

25

18

7

10

1.953

  1. Each factor was examined at 5 levels including (–), (−), (0), (+) and (++) which indicates the highest level
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