Enhanced production of coenzyme Q10 by metabolically engineered Escherichia coli

Coenzyme Q10 (CoQ10) acts as a mobile component of the respiratory chain by playing an essential role in the electron transport system, and has emerged as a valuable molecule for pharmaceutical and cosmetic applications. The biosynthesis of CoQ10 involves at least 14 sequential reactions catalyzed by various enzymes. In the present work, Escherichia coli BW25113 was engineered to produce CoQ10 by removing the endogenous octaprenyl diphosphate synthase gene (IspB) and functionally replacing with a decaprenyl diphosphate synthase gene (RsddsA) from Rhodobacter sphaeroides under the control of T5 promoter using λ red recombination. The ΔIspB::T5-ddsA mutation was introduced into E.coli PG1 (Δpgi T5-dxs;T5- idi;T5-ispDF;ptsG::P119-glk;ΔgalR;ΔlacI ) whose isopentenyl-diphosphate and dimethylallyl-diphosphate precursors were strengthened. In addition, the menB gene involved in menaquinone biosynthesis was further knockout by P1 transduction. The specific CoQ10 content of resulting strain PG1MB is 1.75mg/g dry cell weigh (DCW).Overexpression of individual genes: ddsA, crtE, ubiE, ubiA, ubiDX, ubiH, ubiB and ubiG from R.sphaeroides also showed positive effect on CoQ10 production. Codon optimization and coexpression of ddsA and ubiE from R.sphaeroides under the control of araBAD promoter in a medium-copy plasmid pXB1a could produce CoQ10 up to 3.06 mg/g DCW. However, coexpression of ddsA and ubiE with ubiA, ubiDX, ubiB or ubiG has no effect on CoQ10 production due to metabolic burden. The overexpression of pcak gene encoding pHBA transporter from Acinetobacter calcoaceticus and metK gene encoding S-adenosyl-L-methionine synthetase from R.sphaeroides enhanced CoQ10 content to 3.3mg/g further in the presence of 0.2% L-arabinose, 2mM pHBA and 5mM L-Methionine.