Enhanced production of CoQ10 by constitutive overexpression of 3-demethyl ubiquinone-9 3-methyltransferase under tac promoter in Rhodobacter sphaeroides

Coenzyme Q10 (CoQ10), as an essential electron carrier in the aerobic respiratory electron transfer system, has been proven to be an effective compound in health care and disease prevention. With the aim of improving the production of CoQ10, the biosynthetic pathway of CoQ10 was engineered in Rhodobacter sphaeroides by overexpressing 3-demethyl ubiquinone-9 3-methyltransferase (UbiG), which catalyzes the two steps of O-methylations of the quinonoid ring. For expressing the UbiG, a constitutive expression vector harboring tac promoter and ubiG gene was firstly developed. After cultivated in dark conditions, the transcriptional level of ubiG of the recombinant R. sphaeroides without inducer, which approached to that of with inducer, was about 133 times that of the wild type. The production was correspondingly improved up to 65.8 mg/L compared to 47.6 mg/L for the wild type. In addition, it was found that isopropyl-beta-d-thiogalactopyranoside (IPTG) had a negative effect on CoQ10 production when added to the medium, although it showed no significant influence on the growth rate of the microbes.