Table 2.
Plackett–Burman design: experimental procedure, variables and statistical analysis
| Two-stage Fermentation |
Pre-growth stage (24 h) Initial pH 5 |
Lipase production stage (72 h) Initial biomass concentration: 8 gwet weight /L |
Response variable | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Input variables | Morphology (−) pellets (+) dispersed | Glucose | l-Arabinose | Sucrose | N:C ratio | pH | Oleic acid | Tributirine | CaCl2 | FeCl3 | Olive oil |
Specific lipase activity (U/gdry weight) |
| Level (g/L)a | ||||||||||||
| (−) | 0.5 CaCl2 | 0 | 0 | 5.0 | 0.4 | 5.0 | 0 | 0 | 0 | 0 | 10.0 | |
| (+) | 1.0 FeCl3 | 10.0 | 10.0 | 10.0 | 0.6 | 7.0 | 1.0 | 1.0 | 0.05 | 0.1 | 20.0 | |
| Trial number | ||||||||||||
| 1 | + | − | + | + | − | + | − | − | − | + | + | 33.92 ± 1.53 |
| 2 | − | − | + | + | + | − | + | + | − | + | − | 17.32 ± 3.72 |
| 3 | − | − | − | + | + | + | − | + | + | − | + | 17.88 ± 3.22 |
| 4 | + | + | − | + | − | − | − | + | + | + | − | 11.84 ± 1.94 |
| 5 | − | + | − | − | − | + | + | + | − | + | + | 15.33 ± 0.04 |
| 6 | + | − | − | − | + | + | + | − | + | + | − | 7.61 ± 0.28 |
| 7 | − | − | − | − | − | − | − | − | − | − | − | 3.12 ± 0.07 |
| 8 | − | + | + | + | − | + | + | − | + | − | − | 17.19 ± 3.68 |
| 9 | + | + | − | + | + | − | + | − | − | − | + | 24.47 ± 6.66 |
| 10 | − | + | + | − | + | − | − | − | + | + | − | 11.41 ± 1.51 |
| 11 | + | + | + | − | + | + | − | + | − | − | − | 20.84 ± 5.88 |
| 12 | + | − | + | − | − | − | + | + | + | − | + | 4.75 ± 1.81 |
| Effect | 3.531 | 2.747 | 4.198 | 9.923 | 2.232 | 6.643 | − 2.053 | − 1.625 | − 7.390 | 1.530 | 3.978 | R2 = 92.73% |
| p-value | 0.022 | 0.062 | 0.009 | < 0.001 | 0.121 | < 0.001 | 0.151 | 0.248 | < 0.001 | 0.275 | 0.003 | R2 adj = 86.07% |
Letters in bold show the experimental procedure, variables and statistical analysis corresponding to the pre-growth stage
aConcentration of medium components