Optimization of 1,3-Butanediol Biosynthesis from Glucose through the Inverted Fatty Acid β-Oxidation Pathway by Recombinant Escherichia coli Strains
摘要
In derivatives of the Escherichia coli strain MG1655 ∆ackA-pta, ∆poxB, ∆ldhA, ∆adhE, devoid of mixed-acid fermentation pathways, the expression of native L-1,2-propanediol oxidoreductase and NADPH-dependent aldehyde reductase genes, fucO and yqhD, was enhanced, and the butyraldehyde dehydrogenase gene of Clostridium saccharoperbutylacetonicum, bld, was expressed. The ability to biosynthesize 1,3-butanediol from glucose resulting from a functional reversal of fatty acid β-oxidation was ensured in the recombinants due to the increased expression of the atoB and fadB genes encoding acetyl-CoA C-acetyltransferase and bifunctional (S)-3-hydroxyacyl-CoA dehydrogenase/enoyl-CoA hydratase. Anaerobic substrate to target product conversion of 0.2 mol/mol was achieved with ~4 mM 1,3-butanediol accumulation. When the intracellular availability of NADH equivalents was increased due to constitutive expression of genes of the pyruvate dehydrogenase complex, aceEF-lpdA, the conversion of glucose to 1,3-butanediol increased up to ~0.3 mol/mol with accumulation of the target product at the level of ~7 mM. Enhanced expression of the membrane-bound transhydrogenase genes, pntAB, led to the synthesis of 9.5 mM 1,3-butanediol by the yqhD-overexpressing strain with a yield of 0.4 mol/mol.