Enhancement of carotenoid biosynthesis in Phaffia rhodozyma PR106 under stress conditions.

Carotenoids have good biological activity in antioxidant, anti-aging and scavenging harmful free radicals. In this study, we screened a strain that produced carotenoids, and selected a stress condition which significantly improved carotenoids content. The strain was identified as Phaffia rhodozyma PR106. Active oxygen generator TiO2 was the most significant factor to the carotenoids content of the P. rhodozyma. The content of carotenoids was 54.45 mg/g at 500 mg/L TiO2, which was about 1.25 times of the control and the proportion of carotenoids also changed from 1:9:16 to 1:8.5:12. Further, we determined the reactive oxygen species (ROS) in YEPD medium and P. rhodozyma, found that the ROS (H2O2, O2-, and HO•) was significantly increased at 500 mg/L TiO2 in YEPD medium compared with the control, but increased in P. rhodozyma under 1000 mg/L TiO2 treated. These results suggested that the increase in carotenoids was related to ROS in P. rhodozyma.