Table 2. Plackett-Burman design with low and high levels of selected fifteen elements and response values
| Source | Factor | Symbol (unit) | Coded values |
| -1 | +1 |
| Carbon source | Glucose | X1 (%) | 0.4 | 3 |
| Sucrose | X2 (%) |
| Maltose | X3 (%) |
| Lactose | X4 (%) |
| Fructose | X5 (%) |
| Molasses | X6 (%) |
| Nitrogen source | GOS | X7 (%) | 0.4 | 2 |
| Yeast extract | X8 (%) |
| Tryptone | X9 (%) |
| Peptone | X10 (%) |
| Mineral | K2HPO4 | X11 (%) | 0.2 | 1.0 |
| KH2PO4 | X12 (%) |
| (NH4)2SO4 | X13 (%) |
| etc. | MgSO4 | X14 (%) | 0.02 | 0.1 |
| MnSO4 | X15 (%) |
| Run | X1 | X2 | X3 | X4 | X5 | X6 | X7 | X8 | X9 | X10 | X11 | X12 | X13 | X14 | X15 | Response1) Y (g/L) |
| 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 8.966142 |
| 2 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | 9.0086 |
| 3 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 8.889302 |
| 4 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 9.152288 |
| 5 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 8.799341 |
| 6 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 8.431364 |
| 7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 9.025306 |
| 8 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | 9.113943 |
| 9 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | 8.146128 |
| 10 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | 9.287802 |
| 11 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | -1 | 8.525045 |
| 12 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | 8.585461 |
| 13 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 8.439333 |
| 14 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 8.993436 |
| 15 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | 8.729974 |
| 16 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 9.371068 |
| 17 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 8.720159 |
| 18 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | 8.690196 |
| 19 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 9.113943 |
| 20 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 8.975432 |
| 21 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | -1 | -1 | 1 | 1 | -1 | 1 | 1 | 8.20412 |
| 22 | -1 | 1 | 1 | -1 | -1 | 1 | 1 | 1 | 1 | -1 | 1 | -1 | 1 | -1 | -1 | 9.352183 |
Dry cell weight by Lactobacillus brevis SCML 432 cultivated at 150 rpm, 37℃ for 28 h. The experiments were carried out in triplicate.
1)Response was dry cell weight from L. brevis SCML 432.