Table 3. Central composite design with five levels of selected elements by the result of Plackett-Burman design and response values
| Factor | Symbol(unit) | Coded values |
| -2 | -1 | 0 | +1 | +2 |
| Molasses | X1 (%) | 1.0 | 2.5 | 4.0 | 5.5 | 7.0 |
| Yeast extract | X2 (%) | 0.5 | 1.5 | 2.5 | 3.5 | 4.5 |
| Maltose | X3 (%) | 0.5 | 2.0 | 3.5 | 5.0 | 6.5 |
| Run | X1 | X2 | X3 | Response1)Y (g/L) |
| 1 | -1 | -1 | -1 | 5.38 |
| 2 | 2 | 0 | 0 | 13.38 |
| 3 | 0 | 0 | -2 | 8.05 |
| 4 | 1 | -1 | 1 | 11.04333 |
| 5 | 0 | 0 | 2 | 9.046667 |
| 6 | 1 | 1 | 1 | 11.16 |
| 7 | 0 | 0 | 0 | 8.35 |
| 8 | -1 | 1 | 1 | 6.11 |
| 9 | 1 | -1 | -1 | 11.16 |
| 10 | 0 | 2 | 0 | 8.23 |
| 11 | 0 | -2 | 0 | 8.566667 |
| 12 | -1 | -1 | 1 | 5.53 |
| 13 | -1 | 1 | -1 | 4.53 |
| 14 | 1 | 1 | -1 | 10.33667 |
| 15 | -2 | 0 | 0 | 3.05 |
| 16 | 0 | 0 | 0 | 8.34 |
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 were dry cell weight from L. brevis SCML 432.