Preparation of 11-hexyloxy-9-undecenoic acid from crude castor oil hydrolysates by recombinant Escherichia coli expressing alcohol dehydrogenase and Baeyer-Villiger monooxygenase

Crude castor oil hydrolysates mainly consisting of ricinoleic acid can be biologically converted to 11-hexyloxy-9-undecenoic acid (C₁₈) with an unsaturated bond and an ester bond which is utilized as a fertile chemical platform. The platform chemical of 11-hexyloxy-9-undecenoic acid can be converted to ω-hydroxyundec-9-enoic acid or dicarboxylic acid via simple chemical or biological conversion. In this study, the biotransformation was directly performed from crude castor oil hydrolysates containing 82% ricinoleic acid using the recombinant Escherichia coli BL21 with two plasmids containing Micrococcus luteus alcohol dehydrogenase and Pseudomonas putida KT2440 Baeyer-Villiger monooxygenase, respectively. The recombinant cells were cultured in Riesenberg medium at pH 6.9 and 20°C for 28.5 h. For biotransformation at 35°C for 2 h, 2.54 g/L 11-hexyloxy-9-undecenoic acid was obtained from crude castor oil hydrolysates with the final concentration of 2.98 g/L ricinoleic acid. The yield and volumetric productivity were 81.34% and 1.22 g/L/h, respectively. Herein, direct conversion of crude castor oil hydrolysates to value-added 11-hexyloxy-9-undecenoic acid was successfully demonstrated.