(96a) Engineering Escherichia Coli for Adipic Acid Production

Adipic Acid, six-carbon straight-chain dicarboxylic acid, is linked almost 90% to nylon production by the polycondensation with hexamethylenediamine and further processed into fibers for applications in carpeting, automobile tire cord and clothing. Almost all of the commercial adipic acid is produced from cyclohexane through two sequent oxidation processes. The process is regarded as poor because the yield is low and the chemicals used are not environmentally friendly. Consequently, extensive research has been directed towards developing an alternative, clean process based on microbial production. Here, we reported that Escherichia coli was engineered to produce adipic acid. Three genes of aroZ, aroY and catA from different bacteria with or without codon optimization, which encoded dehdroshikimate dehydratase, protocatechuate decarboxylase and catechol 1, 2-dioxygenase, respectively, were combinatorially assembled into the heterogeneous synthetic pathway and introduced into the cell of E. coli to complete the whole biosynthetic pathway for conversing glucose to cis, cis-muconic aicd, the precursor of adipic aicd, and then cis, cis-muconic acid was hydrogenated into adipic acid. With blocking the pathway to aromatic acid biosynthsis by mutating shikimate dehydrogenase (AroE) and combinatirally regulating the heterogeneous synthetic pathway with different constitute promoter with different strength in E. coli, the production of cis, cis-muconic acid was improved. In the shaking-flask test, 11.2g/L adipic acid was produced from 30g/L glucose. The genetic modification in combination with metabolic evolution was ongoing to further improve adipic acid production in engineered E. coli. Our study showed the potential to provide a rationale for the engineering and commercialization of microorganisms capable of producing adipic acid.