Increasing coenzyme Q10 yield from Rhodopseudomonas palustris by expressing rate-limiting enzymes and blocking carotenoid and hopanoid pathways.

Abstract

Coenzyme Q10 (CoQ10 ), a strong antioxidant, is used extensively in food, cosmetic and medicine industries. A natural producer, Rhodopseudomonas palustris, was engineered to overproduce CoQ10 . For increasing the CoQ10 content, crtB gene was deleted to block the carotenoid pathway. crtB gene deletion led to 33% improvement of CoQ10 content over the wild type strain. However, it was found that the yield of hopanoids was also increased by competing for the precursors from carotenoid pathway with CoQ10 pathway. To further increase the CoQ10 content, hopanoid pathway was blocked by deleting shc gene, resulting in R. palustris [Δshc, ΔcrtB] to produce 4·7mgg-1 DCW CoQ10 , which was 1·2 times higher than the CoQ10 content in the wild type strain. The common strategy of co-expression of rate-limiting enzymes (DXS, DPS and UbiA) was combined with the pathway blocking method resulted in 8·2mgg-1 DCW of CoQ10 , which was 2·9 times higher than that of wild type strain. The results suggested a synergistic effect among different metabolic engineering strategies. This study demonstrates the potential of R. palustris for CoQ10 production and provides viable strategies to increase CoQ10 titer.