Ubiquinone-10 (CoQ(10)) production was performed in a submerged fermenter through the culture of a facultative bacterium-Rhodobacter sphaeroides. Effects of the aerobic-dark cultivation under different dissolved oxygen (DO) levels and the anaerobic-light cultivation of R. sphaeroides on CoQ(10) production were investigated. In the aerobic-dark cultivation, four levels of dissolved oxygen at 60 +/- 5%, 30 +/- 5%, 10 +/- 5% and 0% controlled by the agitation adjustment were performed. The results showed that the anaerobic-light cultivation had a higher CoQ(10) concentration of 18.2 g/L over all the aerobic-dark batches. Among the batches of aerobic-dark cultivation, the maximum CoQ(10) concentration of 10.5 mg/L was observed in the cultivation at 0% dissolved oxygen. The anaerobic-light cultivation (18.2 g/L) had more than 70% increased of CoQ(10) concentration as compared to the maximum CoQ(10) concentration obtained from the aerobic-dark cultivation at 0% DO (10.5 g/L). However, a much longer lag phase in the anaerobic-light batch led to a lower overall CoQ(10) production rate (0.095 mg/L/h) as compared to the value of 0.146 mg/L/h in the batch of aerobic-dark at 0% DO. Except for the long fermentation period, the high energy consumption required from the light irradiation in the anaerobic-light batch led the anaerobic-light cultivation for CoQ(10) production economically uncompetitive. Therefore, the cultivation of R. sphaeroides under the situation of aerobic-dark at 0% DO was suggested to be applied in the scale-up CoQ(10) production. (C) 2007 Elsevier Inc. All rights reserved.