Enhanced synthesis of Coenzyme Q10 by reducing the competitive production of carotenoids in Rhodobacter sphaeroides

Abstract In Rhodobacter sphaeroides , synthesis of coenzyme Q 10 (CoQ 10 ) shares the same precursor geranylgeranyl diphosphate (GGPP) with carotenoids. Therefore, suppression of carotenoids synthesis is supposed to pose positive effects on accumulation of CoQ 10 . In this paper, the carotenogenesis pathway was repressed using two different strategies, deletion of carotenogenic genes and overexpression of ppsR, a transcriptional regulator for photosynthesis genes, respectively. Knockout of carotenoids synthesis ( crt ) genes resulted in undetectable carotenoids as expected. However, the production of CoQ 10 and biomass were both decreased to half as compared to the wild-type strain. In contrast, upon overexpression of ppsR , the production of carotenoids was decreased from 15.7 mg/L to 2.2 mg/L, and the CoQ 10 production and content were enhanced by 28% and 34.2%, respectively. To further enhance the production of CoQ 10 , crtE was constitutively co-overexpressed with ppsR to improve the supply of GGPP as a key precursor for the isoprenoid side chain of CoQ 10 . The CoQ 10 production and content of the resulting strain RspPE were increased to 73.2 mg/L and 5.67 mg/g, respectively, representing 47% and 55% improvement as compared to the wild type. This result demonstrated that appropriate reduction of carotenoids rather than complete blocking could enhance the CoQ 10 production in Rhodobacter. sphaeroides .