Expression of various genes to enhance ubiquinone metabolic pathway in Agrobacterium tumefaciens

Ubiquinone (UQ), a lipid-soluble component, acts as a mobile component of the respiratory chain by playing an essential role in the electron transport system in many organisms, and has been widely used in pharmaceuticals due to its antioxidant property. The biosynthesis of UQ involves 10 sequential reactions brought about by various enzymes. In this study, dps gene, which encodes decaprenyl diphosphate synthase, involved in ubiquinone biosynthesis from Agrobacterium tumefaciens, and coq2 gene of Saccharomyces cerevisiae, ppt1 gene of Schizosaccahromyces pombe and ubiA gene of Escherichia coli, all of them encoding 4-hydroxybenzoate:polyprenyl diphosphate (4-HB:PPP) transferase, were reconfigured into an operon under the control of a single promoter to yield various plasmids including pBIV-dps, pBIV-dpsq, pBIV-dpsp and pBIV-dpsca. The recombinant A. tumefaciens containing dps-ubiC-ubiA gene showed the highest level ubiquinone production than that of the other recombinants and the nonrecombinant bacterium. In an aerobic fed-batch fermentation, A. tumefaciens containing the pBIV-dpsca plasmid produced 25.2 mg of ubiquinone-10 per liter which was 1.68 times higher than that of nonrecombinant type. While in microaerobic fed-batch fermentation, recombinant cell pBIV-dpsca produced 30.8 mg L⁻¹ of ubiquinone-10. Compared to the original A. tumefaciens, the ubiquinone-10 yield and productivities of the recombinant bacterium pBIV-dpsca increased 88.9% and 77.7%, respectively, under microaerobic fed-batch conditions.