Rapid Production of Natural Carotenoids from Rhodobacter sphaeroides

Rhodobacter sphaeroides is abundant in natural carotenoids. However, fermentation under light growth conditions for carotenoids biosynthesis is time consuming. In the present study, fermentation for 36 h under micro-aerobic growth conditions was employed to rapidly produce carotenoids from Rb. Sphaeroides. Orthogonal experiments suggested that the optimal fermentation process was: temperature 33°C, inoculation amount 8%, fermentation duration 36 h. The yield of total carotenoids was 11.542 mg/L. Real-time PCR indicated that expression levels for crtA, crtD, crtE and crtI at the time fermentation for 36 h were higher than that of fermentation for 48 h. TLC analysis showed that at least 6 well separated bands were observed. Temperature, pH and light tolerance tests indicated that the total carotenoids were stable. 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) assay suggested that the total carotenoids exhibited high anti-oxidant activity and the $IC_{50}$ value of DPPH radical scavenging test was about 8.175 μg/mL. The present study will promote to produce natural carotenoids from microorganism in large-scale.