Production of coenzyme Q_(10) using Rhodobacter sphaeroides

Abstract

From the four different samples in Korea, One new photosynthetic bacterium strain was isolated, which was Rhodobacter sphaeroides. The isolated strain was a rod, 1-1.5 μm in size and very motile in the vegetative state. This strain exhibited a much higher CoQ_(10) content than the other strains (1.55 mg/g dry cell) and was the focus of this study. Production of CoQ_(10) was improved by-chemical mutation with 2.94 mg/g dry cell. Under the conditions of 50 Lux, 30℃, 300 rpm, and 5 vvm aeration, R. sphaeroides was cultivated in a 1-L bioreactor at pH 7. The maximum dry-cell weight was obtained at 12 hr of cultivation, and the CoQ_(10) production was at its maximum (1.0 mg/g dry cell). Under the same as conditions above without control pH, the maximum cell mass was obtained at 25 hr, with the highest production of CoQ_(10) (1.69 mg/g dry cell), which was 1.7 times higher than that obtained at controlled pH 7. The effect of light irradiation on the CoQ_(10) production using R. sphaeroides was also investigated in a 1-L bioreactor cultivated without light irradiation, The maximum production of CoQ_(10) was 1.67 mg/g dry cell, which was almost the same as that cultivated with light irradiation. The maximum CoQ_(10) production was 1.69 mg/g dry cell under the conditions of 50 Lux, 30oC, 300 rpm, and 5 vvm aeration. The CoQ_(10) production was improved up to 2.91 mg/g dry cell under the reduced conditions of agitation speed (200 rpm) and aeration rate (0.2 vvm). When R. sphaeroides was cultivated under more reduced DO level during the exponential phase of cell, the CoQ_(10) production of 3.88 mg/g dry cell was obtained maximally. Therefore, the poorer condition of aeration-agitation resulted in higher production of CoQ_(10), and thus DO content was a crucial factor in production of CoQ_(10). After determining the best culture conditions of R. sphaeroides to produce CoQ_(10), Cultivation of R. sphaeroides mutant was carried out in bioreactor 1L. The maximum production of CoQ_(10) and cell mass were 4.66 mg/g dry cell and 3.02 g/L at 24hr of cultivation. The results were obtained in pilot scale almost the same with CoQ_(10) production of 4.63 mg/g dry cell and cell mass of 3.09 g/L as that obtained in bioreactor 1L.