Table 2 Experimental range and levels of independent variables used in central composite design
Independent variables | Range and levels | |||||
|---|---|---|---|---|---|---|
−α | −1 | 0 | 1 | +α | ||
Production medium optimization (g L−1) | ||||||
Cassava starch | Y1 | 3.3 | 5.0 | 7.5 | 10 | 11.7 |
Nitrogen sources | Y2 | 3.3 | 5.0 | 7.5 | 10 | 11.7 |
Sodium carbonate | Y3 | 5.8 | 7.5 | 10.0 | 12.5 | 14.2 |
Optimal operating conditions | ||||||
Aeration (vvm) | Z1 | 1.29 | 1.5 | 2 | 2.5 | 2.7 |
Agitation (rpm) | Z2 | 79.5 | 100 | 150 | 200 | 220.5 |