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. <i>Rhodosporidiobolus odoratu</i>s, a representative oleaginous red yeast, is considered a promising alternative for producing high-value carotenoids including β-carotene, torulene, and torularhodin. Here, the impact of varying concentrations of NaCl treatments on carotenoid contents in <i>R. odoratus</i> XQR after 120 h of incubation was examined. The results indicated that, as compared to the control (59.37 μg/g_dw), the synthesis of total carotenoids was significantly increased and entirely suppressed under low-to-moderate (0.25 mol/L: 68.06 μg/g_dw, 0.5 mol/L: 67.62 μg/g_dw, and 0.75 mol/L: 146.47 μg/g_dw) and high (1.0, 1.25, and 1.5 mol/L: 0 μg/g_dw) concentrations of NaCl treatments, respectively. Moreover, the maximum production of β-carotene (117.62 μg/g_dw), torulene (21.81 μg/g_dw), and torularhodin (7.04 μg/g_dw) was achieved with a moderate concentration (0.75 mol/L) of NaCl treatment. Transcriptomic and metabolomic analyses suggested that the increase in β-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 (<i>atoB</i>, <i>HMGCS</i>, and <i>mvaD</i>), carotenoid biosynthesis (<i>crtYB</i> and <i>crtI</i>), and TCA cycle (<i>pckA</i>, <i>DLAT, pyc, MDH1</i>, <i>gltA</i>, <i>acnA</i>, <i>IDH1/2</i>, <i>IDH3</i>, <i>sucA</i>, <i>sucB</i>, <i>sucD</i>, <i>LSC1</i>, <i>SDHA</i>, and <i>fumA/fumB</i>). The present study not only demonstrates a viable method to concurrently increase the production of β-carotene, torulene, torularhodin, and total carotenoids in <i>R. odoratus</i> XQR, but it also establishes a molecular foundation for further enhancing their production through genetic engineering.