ABSTRACT
Coenzyme Q[10] [CoQ[10]] is an isoprenoid component used widely in nutraceutical industries. Farnesyl diphosphate synthase [FPPS] is a responsible enzyme for biosynthesis of farnesyl diphosphate [FPP], a key precursor for CoQs production. This research involved investigating the effect of FPPS over-expression on CoQs production in engineered CoQ[10]-producing Escherichia coli [E. coli]. Two CoQ[10]-producing strains, as referred to E. coli Ba and E. coli Br, were transformed by the encoding gene for FPPS [ispA] under the control of either the trc or P[BAD] promoters. Over-expression of ispA under the control of P[BAD] promoter led to a relative increase in CoQ[10] production only in recombinant E. coli Br although induction by arabinose resulted in partial reduction of CoQ[10] production in both recombinant E. coli Ba and E. coli Br strains. Over-expression of ispA under the control of stronger trc promoter, however, led to a severe decrease in CoQ[10] production in both recombinant E. coli Ba and E. coli Br strains, as reflected by reductions from 629 +/- 40 to 30 +/- 13 and 564 +/- 28 to 80 +/- 14 micro g/g Dried Cell Weight [DCW], respectively. The results showed high level of FPP reduces endogenous CoQ8 production as well and that CoQs are produced in a complimentary manner, as the increase in production of one decreases the production of the other. The reduction in CoQ[10] production can be a result of Dds inhibition by high FPP concentration. Therefore, more effort is needed to verify the role of intermediate metabolite concentration and to optimize production of CoQ[10]
ABSTRACT
CoQ[10] and lycopene are isoprenoid compounds with nutraceutical and pharmaceutical benefits. In this study, the effect of concomitant lycopene biosynthesis on CoQ[10] accumulation in transformed Escherichia coli DH5 alpha was studied. A lycopene production pathway including geranyl diphosphate synthase [crtE], phytoene synthase [crtB], and phytoene desaturase [crtI] from Erwinia herbicola was constructed in two CoQ[10]-producing E. coli strains. E. coli Ba and E. coli Br containing dds orthologs encoding for decaprenyl diphosphate synthase [Dds], respectively from Agrobacterium tumefaciens and Rhodobacter sphaeroides were transformed by the lycopene pathway resulting in E. coli Ba-lyc and E. coli Br-lyc. The lycopene pathway in E. coli Br-lyc interestingly resulted in a significant increase in CoQ[10] production from 564 +/- 28 to 989 +/- 22 micro g /g DCW. To confirm that the improvement of CoQ[10] production in E. coli Br-lyc was due to lycopene biosynthesis and not just geranylgeranyl diphosphate formation in the lycopene pathway, crtE was only introduced into E. coli Ba and E. coli Br strains. Surprisingly, crtE expression had adverse effects on CoQ[10] production in both strains. The results shed light on the Dds-catalyzed reaction as a bottleneck controlled by precursors; and the efficiency of a parallel lycopene pathway to streamline the flow of metabolites