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Ubiquinones (UQ) are important electron transporters and play lot of important roles in most organisms. In different species, UQ was classified to be UQ-6, 7, 8, 9, 10 according to their polyprenyl side chain length. The side chain's length is determined by the enzyme named Poly-Prenyl diphosphate synthases (PPPS). Bacteria are usually reconstructed to producing UQ-10 used in human's food additive, medicine or cosmetics, such as using decaprenyl Diphosphate Synthase (DPS) gene from R. radiobacter to substitute E.coli's octaprenyl diphosphate synthase gene , just like E. coli BL21 (�� ispB::ddsA) used in this study. It is interesting that not only in these reconstructed bacteria, but in human-being, DPS can synthesize UQ-9 besides UQ-10. The mechanism of this phenomenon is still unknown. In this study, the effects of culture conditions, including the temperature, dissolved oxygen, pH and culture medium, on the DPS characteristics in E. coli BL21 (�� ispB::ddsA) were examined. Results show that temperature greatly affects the ratio of UQ-9/UQ-10, but not the total ubiquinone's production. Increasing dissolved oxygen and protein concentration in culture medium can promote total ubiquinone's production, but not the ratio of UQ-9/UQ-10. These results may give reference for UQ-10's industrial produce and the mechanism of these conditions' effect on DPS will be discussed.