Combined Biocatalytic and Chemical Transformations of Oleic Acid to ω-Hydroxynonanoic Acid and α,ω-Nonanedioic Acid

A practical chemoenzymatic method for the synthesis of 9-hydroxynonanoic acid and 1,9-nonanedioic acid (i.e., azelaic acid) from oleic acid [(9Z)-octadec-9-enoic acid] was investigated. Biotransformation of oleic acid into 9-(nonanoyloxy)nonanoic acid via 10-hydroxyoctadecanoic acid and 10-keto-octadecanoic acid was driven by a C-9 double bond hydratase from Stenotrophomonas maltophilia, an alcohol dehydrogenase from Micrococcus luteus, and a Baeyer–Villiger monooxygenase (BVMO) from Pseudomonas putida KT2440, which was expressed in recombinant Escherichia coli. After production of the ester (i.e., the BVMO reaction product), the compound was chemically hydrolyzed to n-nonanoic acid and 9-hydroxynonanoic acid because n-nonanoic acid is toxic to E. coli. The ester was also converted into 9-hydroxynonanoic acid and the n-nonanoic acid methyl ester, which can be oxygenated into the 9-hydroxynonanoic acid methyl ester by the AlkBGT from P. putida GPo1. Finally, 9-hydroxynonanoic acid was chemically oxidized to azelaic acid with a high yield under fairly mild reaction conditions. For example, whole-cell biotransformation at a high cell density (i.e., 10 g dry cells/L) allowed the final ester product concentration and volumetric productivity to reach 25 mM and 2.8 mM h⁻¹, respectively. The overall molar yield of azelaic acid from oleic acid was 58%, based on the biotransformation and chemical transformation conversion yields of 84% and 68%, respectively. (Figure presented.).