Table 4 Coded values of the variables for the central composite design
From: Photo-biohydrogen production potential of Rhodobacter capsulatus- PK from wheat straw
| Â | Â | Actual values of coded levels | Â | Â | ||
|---|---|---|---|---|---|---|
Variables | Coded symbol | -1 | 0 | 1 | -1.6818 | 1.6818 |
-Inoculum age (h) | X1 | 24 | 48 | 72 | 8.00 | 88 |
Nitrogen content (mg) | X2 | 200 | 300 | 400 | 132 | 468 |
Substrate (g) | X3 | 1.5 | 2.0 | 2.5 | 1.16 | 2.84 |