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Table 2 Experimental design and results of the central composite design

From: A statistical strategy for optimizing the production of α-galactosidase by a newly isolated Aspergillus niger NRC114 and assessing its efficacy in improving soymilk properties

Run pH value Mannose conc. (g/L) Meat extract conc. (g/L) Incubation time (day) α-Galactosidase activity (U/mL)
Actual Predicted Residual
1 5.5 15 7.5 5 22.528 20.166 2.352
2 4.5 12.5 5 6 17.339 17.749 − 0.410
3 5.5 10 7.5 5 16.708 16.199 0.509
4 4.5 7.5 5 6 10.559 11.684 − 1.124
5 5.5 10 7.5 7 22.959 21.118 1.842
6 4.5 7.5 10 4 11.692 12.034 − 0.342
7 6.5 7.5 5 4 7.023 8.342 − 1.319
8 5.5 5 7.5 5 9.046 10.686 − 1.640
9 4.5 12.5 10 6 25.199 25.436 − 0.237
10 5.5 10 12.5 5 19.059 17.469 1.591
11 6.5 12.5 10 4 12.557 12.988 − 0.431
12 6.5 7.5 5 6 12.367 10.581 1.786
13 5.5 10 7.5 5 15.981 16.199 − 0.218
14 5.5 10 7.5 3 8.925 10.055 − 1.130
15 6.5 7.5 10 4 10.828 9.574 1.254
16 5.5 10 7.5 5 16.327 16.199 0.128
17 5.5 10 7.5 5 16.146 16.199 − 0.053
18 6.5 7.5 10 6 15.765 16.815 − 1.050
19 6.5 12.5 5 4 8.579 7.922 0.658
20 3.5 10 7.5 5 16.439 16.696 − 0.257
21 6.5 12.5 10 6 23.219 25.552 − 2.333
22 4.5 12.5 10 4 15.669 16.612 − 0.942
23 4.5 7.5 10 6 15.722 15.536 0.186
24 4.5 12.5 5 4 13.422 13.928 − 0.506
25 7.5 10 7.5 5 12.938 11.969 0.968
26 5.5 10 7.5 5 16.984 16.199 0.785
27 6.5 12.5 5 6 14.269 15.483 − 1.214
28 5.5 10 2.5 5 7.672 8.551 − 0.879
29 5.5 10 7.5 5 15.047 16.199 − 1.151
30 4.5 7.5 5 4 16.362 13.185 3.177