Table 5 Test variables and levels of central composite design (CCD) to optimize glucose concentration, peptone concentration and pH level for the polyhydroxyalkanoate production by Bacillus cereus SH-02
Coded levels | |||||||
|---|---|---|---|---|---|---|---|
ariable | Symbol | Unit | -α (−1.68) | Low (−1) | Middle (0) | High (1) | +α (+ 1.68) |
Glucose concentration | A | g/l | 3.2 | 10 | 20 | 30 | 36.8 |
Peptone concentration | B | g/l | −0.11 | 5 | 12.5 | 20 | 25.11 |
PH levels | C | – | 4.5 | 5.5 | 7 | 8.5 | 9.5 |