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  • Title: Strategies for efficient repetitive production of succinate using metabolically engineered Escherichia coli.
    Author: Ma JF, Jiang M, Chen KQ, Xu B, Liu SW, Wei P, Ying HJ, Chang HN, Ouyang PK.
    Journal: Bioprocess Biosyst Eng; 2011 May; 34(4):411-8. PubMed ID: 21103890.
    Abstract:
    Escherichia coli AFP111, a pflB, ldhA, ptsG triple mutant of E. coli W1485, can be recovered for additional succinate production in fresh medium after two-stage fermentation (an aerobic growth stage followed by an anaerobic production stage). However, the specific productivity is lower than that of two-stage fermentation. In this study, three strategies were compared for reusing the cells. It was found when cells were aerobically cultivated at the end of two-stage fermentation without supplementing any carbon source, metabolites (mainly succinate and acetate) could be consumed. As a result, enzyme activities involved in the reductive arm of tricarboxylic acid cycle and the glyoxylate shunt were enhanced, yielding a succinate specific productivity above g⁻¹(DCW)h⁻¹ and a mass yield above 0.90 g g⁻¹ in the subsequent anaerobic fermentation. In addition, the intracellular NADH of cells subjected to aerobic cultivation with metabolites increased by more than 3.6 times and the ratio of NADH to NAD+ increased from 0.4 to 1.3, which were both favorable for driving the TCA branch to succinate.
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