Lipid and Carotenoid Production by <em>Rhodotorula glutinis</em> with a Combined Cultivation Mode of Nitrogen, Sulfur, and Aluminium Stress

• Main Authors: Nora Elfeky, Mostafa Elmahmoudy, Yue Zhang, JianLi Guo, Yongming Bao
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: Applied Sciences
• Subjects: <i>Rhodotorula glutinis</i>; carotenoid; torulene; lipid; kinetic analysis; fluorescence microscopy; aluminum sulfate
• Online Access: https://www.mdpi.com/2076-3417/9/12/2444

Torulene is a promising pink pigment, produced only by yeasts and fungi, and its production is still in a developing stage due to the low production rate. Accordingly, this study focuses on maximizing torulene production by <i>Rhodotorula glutinis</i> using shaken flask fermentation. The effect of different nitrogen sources, and C/N and C/S ratios on lipid and carotenoid production by <i>R. glutinis</i> was studied using 60 g/L glucose. The largest cells filled with golden fluorescence lipid bodies were observed using fluorescence microscopy when peptone was used as a nitrogen source. The highest total pigment (0.947 mg/L) and carotenoid relative productivity (Car-RP) (89.04 µg/g) were obtained at C/N 146 and C/S 120, and with ammonium sulfate as a nitrogen source, with 62% torulene domination using High Performance Liquid Chromatography (HPLC) for identification. Under a high C/N ratio, regardless of the C/S ratio, the carotenoid synthesis rate decreased after three days while the lipid synthesis rate kept increasing to the sixth day. Interestingly, after adding 0.7 mM Al₂(SO₄)₃ to the optimized medium, the total pigment and Car-RP (2.2 mg/L and 212.9 µg/g) sharply increased, producing around 2.16 mg/L torulene (98%) with around 50% decrease in lipid yield. This is the first report on the role of Al₂(SO₄)₃ for enhancing torulene production under lipogenesis condition, which could be used as a potential tool for torulene production.