Inhibition of Coenzyme Qs Accumulation in Engineered Escherichia coli by High Concentration of Farnesyl Diphosphate

BACKGROUND: 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). METHODS: 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. RESULTS: 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 μg/g Dried Cell Weight (DCW), respectively. The results showed high level of FPP reduces endogenous CoQ ( 8 ) 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. CONCLUSION: 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 ) .