Table 3. Levels and combinations tested in the 5 levels-3 variables central composite designs.
| Levels | pH | Temperature (°C) | Surfactants (%) |
|---|---|---|---|
| −α (−2) | 4 | 10 | 0 |
| −1 | 5 | 20 | 0.5 |
| 0 | 6 | 30 | 1 |
| +1 | 7 | 40 | 1.5 |
| +α (+2) | 8 | 50 | 2 |
| Combinations | |||
| 1 | 7 | 40 | 1.5 |
| 2 | 7 | 40 | 0.5 |
| 3 | 7 | 20 | 1.5 |
| 4 | 7 | 20 | 0.5 |
| 5 | 5 | 40 | 1.5 |
| 6 | 5 | 40 | 0.5 |
| 7 | 5 | 20 | 1.5 |
| 8 | 5 | 20 | 0.5 |
| 9 | 6 | 30 | 1 |
| 10 | 6 | 30 | 0 |
| 11 | 6 | 30 | 2 |
| 12 | 6 | 10 | 1 |
| 13 | 6 | 50 | 1 |
| 14 | 4 | 30 | 1 |
| 15 | 8 | 30 | 1 |
| 16 | 6 | 30 | 0 |
| 17 | 6 | 30 | 0 |
Note:
Levels and combinations tested in the 5 levels-3 variables Central Composite Designs about the effects of pH, temperature and surfactants concentration on biofilm formation by B. infantis DSM20088 and L. reuteri DSM20016.