Coenzyme Q10 production in recombinant Escherichia coli strains engineered with a heterologous decaprenyl diphosphate synthase gene and foreign mevalonate pathway.

Abstract In the present work, Escherichia coli DH5 α was metabolically engineered for CoQ 10 production by the introduction of decaprenyl diphosphate synthase gene ( ddsA ) from Agrobacterium tumefaciens. Grown in 2YTG medium (1.6% tryptone, 1% yeast extract, 0.5% NaCl, and 0.5% glycerol) with an initial pH of 7, the recombinant E. coli was capable of CoQ 10 production up to 470 μg/gDCW (dry cell weight). This value could be further elevated to 900 μg/gDCW simply by increasing the initial culture pH from 7 to 9. Supplementation of 4-hydroxy benzoate did not improve the productivity any further. However, engineering of a lower mevalonate semi-pathway so as to increase the isopentenyl diphosphate (IPP) supply of the recombinant strain using exogenous mevalonate efficiently increased the CoQ 10 production. Lower mevalonate semi-pathways of Staphylococcus aureus , Streptococcus pyogenes , Streptococcus pneumoniae , Enterococcus faecalis , and Saccharomyces cerevisiae were tested. Among these, the pathway of Streptococcus pneumoniae proved to be superior, yielding CoQ 10 production of 2700±115 μg/gDCW when supplemented with exogenous mevalonate of 3 mM. In order to construct a complete mevalonate pathway, the upper semi-pathway of the same bacterium, Streptococcus pneumoniae , was recruited. In a recombinant E. coli DH5 α harboring three plasmids encoding for upper and lower mevalonate semi-pathways as well as DdsA enzyme, the heterologous mevalonate pathway could convert endogenous acetyl-CoA to IPP, resulting in CoQ 10 production of up to 2428±75 μg/gDCW, without mevalonate supplementation. In contrast, a whole mevalonate pathway constructed in a single operon was found to be less efficient. However, it provided CoQ 10 production of up to 1706±86 μg/gDCW, which was roughly 1.9 times higher than that obtained by ddsA alone.