Metabolic impact of the level of aeration during cell growth on anaerobic succinate production by an engineered Escherichia coli strain.

The metabolic impact of two different aeration conditions during the growth phase on anaerobic succinate production by the high succinate producer Escherichia coli SBS550MG (pHL413) was investigated. Gene expression profiles, metabolites concentrations and metabolic fluxes were analyzed. Different oxygen levels are known to induce or repress transcription, synthesis of different enzymes, or both, affecting cell metabolism and thus product yield and productivity. The succinate yield was 1.55 and 1.25 mol succinate/mol glucose, and the productivity was 1.3 and 0.9 g L(-1)h(-1)) for the low aeration experiment and high aeration experiment, respectively. Changes in the level of aeration during the cells growth phase significantly modified gene expression profiles and metabolic fluxes in this system. Pyruvate was accumulated during the anaerobic phase in the high aeration experiment, which could be explained by a lower pflAB expression during the transition time and a lower flux towards acetyl-CoA during the anaerobic phase compared to the low aeration case. The higher PflAB flux and the higher expression of genes related to the glyoxylate shunt (aceA, aceB, acnA, acnB) during the transition time, anaerobic phase, or both, improved succinate yield in the low aeration case, allowing the system to attain the maximum theoretical succinate yield for E. coli SBS550MG (pHL413).