Transcriptomic and metabolomic analyses reveal the positive effect of moderate concentration of sodium chloride treatment on the production of β-carotene, torulene, and torularhodin in oleaginous red yeast Rhodosporidiobolus odoratus XQR

Carotenoids, a family of lipid-soluble pigments, have garnered growing interest for their health-promoting benefits and are widely utilized in the food, feed, pharmaceutical, and cosmetic industries. Rhodosporidiobolus odoratus, s, a representative oleaginous red yeast, is considered a promising alternative for producing high-value carotenoids including R-carotene, torulene, and torularhodin. Here, the impact of varying concentrations of NaCl treatments on carotenoid contents in R. odoratus XQR after 120 h of incubation was examined. The results indicated that, as compared to the control (59.37 mu g/g(dw)), the synthesis of total carotenoids was significantly increased and entirely suppressed under low-to-moderate (0.25 mol/L: 68.06 mu g/g(dw), 0.5 mol/L: 67.62 mu g/g(dw), and 0.75 mol/L: 146.47 mu g/g(dw)) and high (1.0, 1.25, and 1.5 mol/L: 0 mu g/g(dw)) concentrations of NaCl treatments, respectively. Moreover, the maximum production of R-carotene (117.62 mu g/g(dw)), torulene (21.81 mu g/g(dw)), and torularhodin (7.04 mu g/g(dw)) was achieved with a moderate concentration (0.75 mol/L) of NaCl treatment. Transcriptomic and metabolomic analyses suggested that the increase in R-carotene, torulene, and torularhodin production might be primarily attributed to the up-regulation of some key protein-coding genes involved in the terpenoid backbone biosynthesis (atoB , HMGCS, , and mvaD), carotenoid biosynthesis (crtYB and crtI), and TCA cycle (pckA, DLAT, pyc, MDH1, gltA, acnA, IDH1/2, IDH3, sucA, sucB, sucD, LSC1, SDHA, and fumA/fumB). The present study not only demonstrates a viable method to concurrently increase the production of R-carotene, torulene, torularhodin, and total carotenoids in R. odoratus XQR, but it also establishes a molecular foundation for further enhancing their production through genetic engineering.