Ultraviolet-diethyl sulfate composite mutagenesis of Rhodosporidium toruloides and culture optimization to improve carotenoid production

Rhodosporidium toruloides is a carotenoid-producing oleaginous yeast, and its carotenoids are of considerable value to food, chemical, and medical industries. In this study, to improve carotenoid production capacity, the parent R. toruloides strain (CK) was compound mutagenized using ultraviolet-diethyl sulfate (UV-DES), and cultivation conditions were simultaneously optimized to enhance the carotenoid synthesis ability of the mutant strain (M5). The carotenoid content was significantly increased following UV-DES compound mutagenesis (CK = 249.34 μg/g, M5 = 535.28 μg/g). The carotenoid content of M5 was increased to 763.85 μg/g under optimal culture conditions. In addition, mutagenesis altered the carotenoid components, and torulene and torularhodin levels were also increased following mutation, leading to changes in antioxidant capacity. Real-time quantitative PCR results showed that expression of six genes (CAR1, CAR2, CrtE, CrtI, ME1, HMG1) related to carotenoid accumulation were significantly upregulated by UV-DES composite mutagenesis. In conclusion, combined UV-DES mutagenesis and optimal culture conditions promoted the biosynthesis of carotenoids in R. toruloides.