Table 3.
Glucose (Glc) consumption rate (GCR), molar yield and productivity of 2,3-butanediol (2,3-BD), and carbon recovery (CR) by the control and engineered C. glutamicum strains
| GCR (nmol min−1 mg CDW−1) | Yield (mol 2,3-BD per mol Glc) | Productivity (nmol min−1 mg CDW−1) | CR (%) | |
|---|---|---|---|---|
| ΔldhA (pEKEx2)* | 2.5 ± 0.4 | 0.05 ± 0.00# | 0.12 ± 0.01 | 81 ± 3 |
| ΔldhA (pEKEx2- als,aldB,butA)* | 4.4 ± 0.4 | 0.34 ± 0.04 | 1.28 ± 0.09 | 79 ± 9 |
| ΔldhA (pEKEx2) | 3.0 ± 0.2 | 0.02 ± 0.01# | 0.06 ± 0.03 | 77 ± 1 |
| ΔldhA (pEKEx2- als,aldB,butA) | 3.4 ± 0.4 | 0.27 ± 0.06 | 0.53 ± 0.13 | 82 ± 3 |
| ΔaceEΔpqoΔldhA (pEKEx2) | 1.6 ± 0.3 | 0.22 ± 0.01# | 0.30 ± 0.00 | 87 ± 1 |
| ΔaceEΔpqoΔldhA (pEKEx2-als,aldB,butA) | 5.4 ± 0.7 | 0.66 ± 0.05 | 3.55 ± 0.58 | 84 ± 7 |
| ΔaceEΔpqoΔldhA (pEKEx2-als,aldB, Ptuf butA) | 6.1 ± 0.1 | 0.61 ± 0.06 | 3.13 ± 0.22 | 87 ± 3 |
| ΔaceEΔpqoΔldhAΔmdh (pEKEx2) | 1.6 ± 0.3 | 0.34 ± 0.05# | 0.53 ± 0.00 | 91 ± 6 |
| ΔaceEΔpqoΔldhAΔmdh (pEKEx2-als,aldB,butA) | 6.0 ± 0.3 | 0.64 ± 0.09 | 4.34 ± 0.16 | 90 ± 4 |
| ΔaceEΔpqoΔldhAΔmdh (pEKEx2-als,aldB, Ptuf butA) | 6.5 ± 0.5 | 0.64 ± 0.10 | 4.25 ± 0.41 | 91 ± 7 |
In the first phase, cells were grown aerobically on 1 % (wt/vol) potassium acetate except for the strains indicated with an asterisk for which 0.5 % (wt/vol) glucose was used instead. Second phase fermentations were carried out for 48 h, using 25 mL of cell suspension in closed 50-mL falcon flasks with glucose as substrate. The cardinal symbol indicates that optically active 2,3-BD was produced; remaining strains produced meso-form of 2,3-BD. Values are averages of at least three independent experiments. A single NMR spectrum was acquired for each sample