Metabolic engineering of Escherichia coli for 1,3-butanediol biosynthesis through the inverted fatty acid β-oxidation cycle

The feasibility of 1,3-butanediol biosynthesis through the inverted cycle of fatty acid β-oxidation in Escherichia coli cells was investigated by the rational metabolic engineering approach. CoA-dependent aldehyde dehydrogenase MhpF and alcohol dehydrogenases FucO and YqhD were used as terminal enzymes catalyzing conversion of 3-hydroxybutyryl-CoA to 1,3-butanediol. Constitutive expression of the corresponding genes in E. coli strains, which are deficient in mixed acid fermentation pathways and expressing fàd regulon genes under control of P ₜᵣc₋ᵢdₑₐₗ₋₄ promoter, did not lead to the synthesis of 1,3-butanediol during anaerobic glucose utilization. Additional inactivation of fadE and ydiO genes, encoding acyl-CoA dehydrogenases, also did not cause synthesis of the target product. Constitutive expression of aceEF-lpdA operon genes encoding enzymes of pyruvate dehydrogenase complex led to an increase in anaerobic synthesis of ethanol. Synthesis of 1,3-butanediol was observed with the overexpression of acetyl-CoA C-acetyltransferase AtoB. Constitutive expression of atoB gene in a strain with a basal expression of alcohol/aldehyde dehydrogenase leads to synthesis of 0.3 mM of 1,3-butanediol.