Production of succinate by a pflB ldhA double mutant of Escherichia coli overexpressing malate dehydrogenase |
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Authors: | Wei Wang Zhimin Li Jingli Xie Qin Ye |
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Affiliation: | (1) State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, 200237 Shanghai, China |
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Abstract: | The gene encoding malate dehydrogenase (MDH) was overexpressed in a pflB ldhA double mutant of Escherichia coli, NZN111, for succinic acid production. With MDH overexpression, NZN111/pTrc99A-mdh restored the ability to metabolize glucose anaerobically and 0.55 g/L of succinic acid was produced from 3 g/L of glucose in shake flask culture. When supplied with 10 g/L of sodium bicarbonate (NaHCO3), the succinic acid yield of NZN111/pTrc99A-mdh reached 1.14 mol/mol glucose. Supply of NaHCO3 also improved succinic acid production by the control strain, NZN111/pTrc99A. Measurement of key enzymes activities revealed that phosphoenolpyruvate (PEP) carboxykinase and PEP carboxylase in addition to MDH played important roles. Two-stage culture of NZN111/pTrc99A-mdh was carried out in a 5-L bioreactor and 12.2 g/L of succinic acid were produced from 15.6 g/L of glucose. Fed-batch culture was also performed, and the succinic acid concentration reached 31.9 g/L with a yield of 1.19 mol/mol glucose. |
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Keywords: | Escherichia coli Malate dehydrogenase Bicarbonate Succinic acid Two-stage culture |
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