Table 2.
Results for cell growth (measured by absorbance at 600 nm and converted to g (dry cell)/L) of E. coli BL21 (DE3) Star™/pAE/LigB (131-645aa), yield (mg/L) and productivity ((mg/L)/h) of soluble recombinant LigB (131-645aa) expressed in shaking flasks at 28°C for 4 h in TB using central composite design for two variables (Abs ind and IPTG for induction) with triplicate at the central point (CP)
| Induction conditions | Cell growth (4 h ind) | Soluble LigB expression (4 h ind) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Assays | Total process time (h) a | Abs ind(x 1) | IPTG (x 2) | Abs 600nm | Dry cell (g/L) | Model (g/L) b | Yield (mg/L) | Model (mg/L) b | Productivity (mg/L)/h | Model ((mg/L)/h) b | pH | Residual glucose (g/L) |
| 1 | 5.75 | 0.75 (-1) | 0.1 mM (-1) | 3.75 | 0.9 | 0.94 (-4.4%) | 180 | 177 (2%) | 31.3 | 31.2 (0.4%) | 6.64 | 6.4 |
| 2 | 5.83 | 0.75 (-1) | 1.0 mM (+1) | 3.31 | 0.8 | 0.74 (7.5%) | 166 | 163 (2%) | 28.4 | 28.4 (0.1%) | 6.75 | 6.8 |
| 3 | 6.75 | 2.0 (+1) | 0.1 mM (-1) | 6.33 | 1.6 | 1.54 (3.8%) | 288 | 286 (1%) | 42.7 | 42.6 (0.2%) | 6.36 | 5.2 |
| 4 | 7.00 | 2.0 (+1) | 1.0 mM (+1) | 5.19 | 1.3 | 1.34 (-3.1%) | 221 | 218 (1%) | 31.5 | 31.4 (0.5%) | 6.24 | 5.1 |
| CP 1c | 6.25 | 1.4 (0) | 0.55 mM (0) | 4.83 | 1.2 | 1.14 (5.0%) | 198 | 211 (-7%) | 31.7 | 33.4 (-5.4%) | 6.63 | 6.4 |
| CP 2 | 6.25 | 1.4 (0) | 0.55 mM (0) | 4.46 | 1.1 | 1.14 (-3.6%) | 214 | 211 (1%) | 34.2 | 33.4 (2.4%) | 6.53 | 5.8 |
| CP 3 | 6.25 | 1.4 (0) | 0.55 mM (0) | 4.53 | 1.1 | 1.14 (-3.6%) | 210 | 211 (-1%) | 33.6 | 33.4 (0.6%) | 6.55 | 5.1 |
aTotal process time = growth time + 4 h induction. The growth time varied according to the time each culture took to reach the Absind required for the addition of IPTG and induction of LigB (131-645aa).
bModel response obtained for each variable with its relative error in parenthesis (% = ((experimental data - predicted by model)/experimental data) x 100).
cCP is the central point, calculated as the intermediate condition between the inferior (-1) and superior levels (+1) and coded as 0, according to experimental design procedures.
The calculated errors were lower than 12%.