Functional characterization of reversed β-Oxidation pathway in Escherichia coli for the production of adipic acid

Adipic acid is the most important straight-chain C6 dicarboxylic acid which is linked almost 90% to nylon production with hexamethylenediamine. Combinatorial assemble of the homologous and heterogeneous genes into the synthetic pathway in Escherichia coli to the complete metabolic pathway for converting glucose into acetyl-CoA and succinyl-CoA via glycolysis and TCA cycle, and then convert them into adipic acid. We have identified novel synthetic pathway genes and assembled them into adipic acid via five metabolic reactions. The identified C6 dicarboxylic acid pathway starts with the TCA intermediates, acetyl-CoA and succinyl-CoA, which subsequently condense into 3-oxoadipyl-CoA by 3-oxoadipyl-CoA thiolase, a reduction reaction forms 3-hydroxyladipyl-CoA by 3-hydroxyladipyl-CoA dehydrogenase, a dehydration reaction further converts them into 5-carboxypentanoyl-CoA. The final dehydrogenation of adipyl-CoA shows our pathway intermediates can form reverse β-oxidation end products such as dicarboxyl-CoAs and the ω-oxidation forms adipic acid. This work provides the progress towards bio-based production of adipic acid.