Table 3.
Experimental design and results of the Plackett-Burman design.
| Trials | Variable levels | Yield (mg/L) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| X 1 | X 2 | X 3 | X 4 | X 5 | X 6 | X 7 | X 8 | X 9 | X 10 | Observed | Predicted | |
| 1 | 1 | −1 | 1 | 1 | −1 | −1 | −1 | −1 | 1 | −1 | 88.38 ± 3.84 | 90.91 |
| 2 | 1 | 1 | −1 | 1 | 1 | −1 | −1 | −1 | −1 | 1 | 117.96 ± 2.37 | 115.41 |
| 3 | −1 | 1 | 1 | −1 | 1 | 1 | −1 | −1 | −1 | −1 | 97.42 ± 6.78 | 96.55 |
| 4 | −1 | −1 | 1 | 1 | −1 | 1 | 1 | −1 | −1 | −1 | 101.79 ± 3.41 | 98.33 |
| 5 | 1 | −1 | −1 | 1 | 1 | −1 | 1 | 1 | −1 | −1 | 102.43 ± 3.74 | 99.73 |
| 6 | 1 | 1 | −1 | −1 | 1 | 1 | −1 | 1 | 1 | −1 | 92.45 ± 3.96 | 94.17 |
| 7 | 1 | 1 | 1 | −1 | −1 | 1 | 1 | −1 | 1 | 1 | 107.47 ± 9.89 | 104.83 |
| 8 | 1 | 1 | 1 | 1 | −1 | −1 | 1 | 1 | −1 | 1 | 121.38 ± 2.26 | 124.57 |
| 9 | −1 | 1 | 1 | 1 | 1 | −1 | −1 | 1 | 1 | −1 | 119.62 ± 2.27 | 117.05 |
| 10 | 1 | −1 | 1 | 1 | 1 | 1 | −1 | −1 | 1 | 1 | 88.76 ± 5.85 | 90.81 |
| 11 | −1 | 1 | −1 | 1 | 1 | 1 | 1 | −1 | −1 | 1 | 119.63 ± 5.56 | 123.21 |
| 12 | 1 | −1 | 1 | −1 | 1 | 1 | 1 | 1 | −1 | −1 | 79.81 ± 4.77 | 80.87 |
| 13 | −1 | 1 | −1 | 1 | −1 | 1 | 1 | 1 | 1 | −1 | 118.85 ± 5.84 | 120.81 |
| 14 | −1 | −1 | 1 | −1 | 1 | −1 | 1 | 1 | 1 | 1 | 76.33 ± 3.15 | 77.53 |
| 15 | −1 | −1 | −1 | 1 | −1 | 1 | −1 | 1 | 1 | 1 | 82.21 ± 2.79 | 80.17 |
| 16 | −1 | −1 | −1 | −1 | 1 | −1 | 1 | −1 | 1 | 1 | 77.19 ± 4.41 | 76.27 |
| 17 | 1 | −1 | −1 | −1 | −1 | 1 | −1 | 1 | −1 | 1 | 62.37 ± 5.76 | 61.05 |
| 18 | 1 | 1 | −1 | −1 | −1 | −1 | 1 | −1 | 1 | −1 | 106.22 ± 7.25 | 104.95 |
| 19 | −1 | 1 | 1 | −1 | −1 | −1 | −1 | 1 | −1 | 1 | 90.56 ± 2.95 | 90.05 |
| 20 | −1 | −1 | −1 | −1 | −1 | −1 | −1 | −1 | −1 | −1 | 60.31 ± 3.20 | 63.93 |
Each experiment was repeated three times, and all of the data were expressed as means ± standard deviations. X 1, X 2, X 3, X 4, X 5, X 6, X 7, X 8, X 9, and X 10 represent peptone (g/L), corn powder (g/L), starch (g/L), soybean meal (g/L), KH2PO4 (g/L), (NH4)2SO4 (g/L), incubation temperature (°C), initial pH, incubation time (h), and inoculum size (%).