Table 2.
Variables and test levels for Plackett-Burman experiment.
| Number | Variables | Code levels | Estimate | t-value | P value | Significance | |
|---|---|---|---|---|---|---|---|
| −1 | 1 | ||||||
| X 1 | Peptone (g/L) | 8 | 12 | 2.33 | 1.01 | 0.3851 | |
| X 2 | Corn powder (g/L) | 20 | 30 | 27.20 | 11.83 | 0.0013 | ∗ |
| X 3 | Starch (g/L) | 10 | 20 | 3.19 | 1.39 | 0.2594 | |
| X 4 | Soybean meal (g/L) | 24 | 36 | 21.09 | 9.17 | 0.0027 | ∗ |
| X 5 | KH2PO4 (g/L) | 3 | 6 | 3.21 | 1.39 | 0.2575 | |
| X 6 | (NH4)2SO4 (g/L) | 3 | 6 | −0.96 | −0.42 | 0.7038 | |
| X 7 | Incubation temperature (°C) | 28 | 34 | 11.11 | 4.83 | 0.0169 | ∗ |
| X 8 | Initial pH | 6.5 | 8.5 | −1.91 | −0.83 | 0.0466 | |
| X 9 | Incubation time (h) | 28 | 40 | 0.38 | 0.17 | 0.8786 | |
| X 10 | Inoculum size (%) | 1 | 3 | −2.34 | −1.01 | 0.3834 | |
∗ indicates model terms are significant.