title: Eliminating side products and increasing succinate yields in engineered strains of Escherichia coli C.
abstract: Derivatives of Escherichia coli C were previously described for succinate production by combining the deletion of genes that disrupt fermentation pathways for alternative products (ldhA::FRT, adhE::FRT, ackA::FRT, focA-pflB::FRT, mgsA, poxB) with growth-based selection for increased ATP production. The resulting strain, KJ073, produced 1.2 mol of succinate per mol glucose in mineral salts medium with acetate, malate, and pyruvate as significant co-products. KJ073 has been further improved by removing residual recombinase sites (FRT sites) from the chromosomal regions of gene deletion to create a strain devoid of foreign DNA, strain KJ091(DeltaldhA DeltaadhE DeltaackA DeltafocA-pflB DeltamgsA DeltapoxB). KJ091 was further engineered for improvements in succinate production. Deletion of the threonine decarboxylase (tdcD; acetate kinase homologue) and 2-ketobutyrate formate-lyase (tdcE; pyruvate formate-lyase homologue) reduced the acetate level by 50% and increased succinate yield (1.3 mol mol(-1) glucose) by almost 10% as compared to KJ091 and KJ073. Deletion of two genes involved in oxaloacetate metabolism, aspartate aminotransferase (aspC) and the NAD(+)-linked malic enzyme (sfcA) (KJ122) significantly increased succinate yield (1.5 mol mol(-1) glucose), succinate titer (700 mM), and average volumetric productivity (0.9 g L(-1) h(-1)). Residual pyruvate and acetate were substantially reduced by further deletion of pta encoding phosphotransacetylase to produce KJ134 (DeltaldhA DeltaadhE DeltafocA-pflB DeltamgsA DeltapoxB DeltatdcDE DeltacitF DeltaaspC DeltasfcA Deltapta-ackA). Strains KJ122 and KJ134 produced near theoretical yields of succinate during simple, anaerobic, batch fermentations using mineral salts medium. Both may be useful as biocatalysts for the commercial production of succinate.
authors.affiliation: Department of Chemical Engineering, University of Florida, Gainesville, Florida.
authors.forename: Kaemwich
authors.initials: K
authors.lastname: Jantama
authors.forename: Xueli
authors.initials: X
authors.lastname: Zhang
authors.forename: J C
authors.initials: JC
authors.lastname: Moore
authors.forename: K T
authors.initials: KT
authors.lastname: Shanmugam
authors.forename: S A
authors.initials: SA
authors.lastname: Svoronos
authors.forename: L O
authors.initials: LO
authors.lastname: Ingram
mesh_terms: D000085:Acetates / Q000378:metabolism; D000217:Acyltransferases / Q000235:genetics; D000426:Alcohol Dehydrogenase / Q000235:genetics; D000429:Alcohol Oxidoreductases / Q000235:genetics; D000445:Aldehyde Oxidoreductases / Q000235:genetics; D000693:Anaerobiosis / Q000235:genetics; D001219:Aspartate Aminotransferases / Q000235:genetics; D019757:Carbon-Oxygen Lyases / Q000235:genetics; D002262:Carboxy-Lyases / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005285:Fermentation / Q000235:genetics*; D017353:Gene Deletion; D024861:Genetic Enhancement / Q000379:methods*; D005947:Glucose / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics; D007770:L-Lactate Dehydrogenase / Q000235:genetics; D000080864:Lactate Dehydrogenase 5; D008291:Malate Dehydrogenase / Q000235:genetics; D008293:Malates / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics; D009097:Multienzyme Complexes / Q000235:genetics; D010709:Phosphate Acetyltransferase / Q000235:genetics; D011771:Pyruvate Oxidase / Q000235:genetics; D011773:Pyruvates / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism*; D013912:Threonine / Q000235:genetics / Q000378:metabolism
chemical_list: D000085:Acetates; D029968:Escherichia coli Proteins; C088103:FocA protein, E coli; D007527:Isoenzymes; D008293:Malates; D026901:Membrane Transport Proteins; D009097:Multienzyme Complexes; D011773:Pyruvates; D013912:Threonine; D019802:Succinic Acid; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase; C068383:adhE protein, E coli; D007770:L-Lactate Dehydrogenase; D000080864:Lactate Dehydrogenase 5; D008291:Malate Dehydrogenase; C046446:malate dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); D000445:Aldehyde Oxidoreductases; D011771:Pyruvate Oxidase; D000217:Acyltransferases; C111105:tdcE protein, E coli; D010709:Phosphate Acetyltransferase; D001219:Aspartate Aminotransferases; D002262:Carboxy-Lyases; D019757:Carbon-Oxygen Lyases; C021578:methylglyoxal synthase; D005947:Glucose