title: pH and base counterion affect succinate production in dual-phase Escherichia coli fermentations.
abstract: Succinate production was studied in Escherichia coli AFP111, which contains mutations in pyruvate formate lyase (pfl), lactate dehydrogenase (ldhA) and the phosphotransferase system glucosephosphotransferase enzyme II (ptsG). Two-phase fermentations using a defined medium at several controlled levels of pH were conducted in which an aerobic cell growth phase was followed by an anaerobic succinate production phase using 100% (v/v) CO(2). A pH of 6.4 yielded the highest specific succinate productivity. A metabolic flux analysis at a pH of 6.4 using (13)C-labeled glucose showed that 61% of the PEP partitioned to oxaloacetate and 39% partitioned to pyruvate, while 93% of the succinate was formed via the reductive arm of the TCA cycle. The flux distribution at a pH of 6.8 was also analyzed and was not significantly different compared to that at a pH of 6.4. Ca(OH)(2) was superior to NaOH or KOH as the base for controlling the pH. By maintaining the pH at 6.4 using 25% (w/v) Ca(OH)(2), the process achieved an average succinate productivity of 1.42 g/l h with a yield of 0.61 g/g.
authors.affiliation: Center for Molecular BioEngineering, University of Georgia, Athens, GA 30602, USA.
authors.forename: Shiying
authors.initials: S
authors.lastname: Lu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Eiteman
authors.forename: Elliot
authors.initials: E
authors.lastname: Altman
mesh_terms: D000693:Anaerobiosis; D002126:Calcium Hydroxide / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000378:metabolism; D017680:Potassium Compounds / Q000378:metabolism; D012972:Sodium Hydroxide / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods; D019802:Succinic Acid / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D003470:Culture Media; D006878:Hydroxides; D017680:Potassium Compounds; D002245:Carbon Dioxide; D012972:Sodium Hydroxide; D019802:Succinic Acid; D005947:Glucose; D002126:Calcium Hydroxide; C029943:potassium hydroxide