In this study, we identified UbiE and UbiH in addition to UbiG
as the key enzymes in the ubiquinone modification pathway of R.
sphaeroides, which updated the pathway information in this
organism and facilitated further metabolic engineering.
Fig. 7. Summary of CoQ10 production improvement in R. sphaeroides recombinant
strains by engineering the quinone modification pathway with different strategies.
The ideal line represents the idealized situation where both the biomass and the
CoQ10 productivity are maximized.
Fig. 8. Fermentation results of R. sphaeroides recombinants with MEP and QMP coengineered.
The solid bars represent the CoQ10 productivity and the open bars
represent the biomass. All the data are shown as mean7SD from three independent
experiments. *po0.05, **po0.01.
214 W. Lu et al. / Metabolic Engineering 29 (2015) 208–216
Intermediates, in addition to the desired product and cell
growth, are important indicators for the efficiency of pathway
engineering. In this study, the accumulation of intermediate 10pMMBQ
indicated the blocking of the engineered pathway by the
UbiF enzyme, which guided the subsequent intermediate removal
and pathway optimization by metabolic engineering with different
strategies. Intermediate analysis in combination with measurement
of cell growth and CoQ10 production formed a comprehensive
assessment system for the performance of the engineered
pathways, providing important guidance for the design-build-testbased
metabolic engineering procedure. After fine tuning of
QMP, and in combination with MEP engineering, we successfully
obtained recombinants with a CoQ10 production of up to 138 mg/L