Table 1.
The production of organic acids by C. glutamicum strains under oxygen deprivationa
| Strains | Glucose (mM/h) | Lactic acid (mM) | Succinic acid (mM) | Acetic acid (mM) | Lactic acid Yield (%)b | Pyk activity (mU/mg)c |
|---|---|---|---|---|---|---|
| WT | 28.46 ± 0.56 | 126.18 ± 1.70 | 22.59 ± 1.65 | 5.17 ± 0.05 | 73.90 ± 0.99 | 471.06 ± 6.61 (418.56 ± 6.54)* |
| WTΔpyk1 | 27.72 ± 0.28 | 109.90 ± 4.00* | 44.49 ± 0.88* | 5.89 ± 0.91 | 66.09 ± 2.41* | 69.98 ± 5.00* (11.34 ± 0.42)* |
| WTΔpyk2 | 29.75 ± 0.11 | 117.30 ± 2.31* | 38.02 ± 0.82* | 5.35 ± 0.76 | 65.71 ± 1.29* | 402.29 ± 8.98* (406.87 ± 14.69) |
| WTΔpyk1Δpyk2 | 28.83 ± 0.38 | 98.80 ± 1.11* | 47.83 ± 0.86* | 6.06 ± 0.64 | 57.12 ± 0.64* | ND (ND) |
| WTΔpyk1Δpyk2/pXMJ19 | 29.51 ± 0.43 | 99.17 ± 2.31* | 49.45 ± 1.69* | 4.40 ± 1.80 | 56.02 ± 1.30* | ND |
| WTΔpyk1Δpyk2/pXMJ19-pyk1 | 29.81 ± 0.85 | 127.29 ± 3.57 | 28.42 ± 3.13* | 6.30 ± 2.19 | 71.16 ± 1.99 | 472.94 ± 21.29 |
| WTΔpyk1Δpyk2/pXMJ19-pyk2 | 29.69 ± 1.20 | 128.77 ± 2.22 | 29.11 ± 5.13* | 6.23 ± 2.07 | 72.28 ± 1.25 | 442.72 ± 10.64 |
| WT/pXMJ19 | 29.63 ± 0.56 | 125.44 ± 4.00 | 27.59 ± 0.76* | 6.72 ± 1.16 | 70.56 ± 2.25 | 486.38 ± 31.68 |
| WT/pXMJ19-pyk1 | 32.78 ± 0.74* | 150.98 ± 2.94* | 13.37 ± 0.14* | 12.78 ± 1.29* | 76.77 ± 1.49* | 926.55 ± 63.96* |
| WT/pXMJ19-pyk2 | 33.58 ± 0.28* | 146.17 ± 3.20* | 19.20 ± 1.27* | 15.38 ± 0.89* | 72.54 ± 1.59 | 911.45 ± 31.86* |
aThe cells were suspended to a final dry cell weight of 10 g/L in 100 mL of CGXII medium with 100 mM bicarbonate. The values were analyzed after 3 h under oxygen deprivation. The data were derived from experiments performed at least in three times, and the error bars represent the standard deviations
bThe yields were calculated as a percentage of the theoretical yield (100% represented 2 mol of lactic acid per 1 mol of glucose consumed)
cPyk activities were measured under oxygen deprivation as described above. And the values in parentheses show the Pyk activities at the exponential growth phase under aerobic conditions. ND, not detected
*,significant differences between WT and mutants under oxygen deprivation analyzed by t-test (P < 0.05) were marked. And the differences of Pyk activities of strains between aerobic and oxygen-deprived conditions are also shown (P < 0.05)