Enhanced Carotenoid Production by Rhodotorula mucilaginosa Cultivated Under LED Illumination in a Photobioreactor

The effect of LED light on carotenoid production by new isolated R. mucilaginosa was evaluated, aiming to develop a more efficient cultivation system. Inoculum preparation involved culturing the strain in a defined medium containing glucose, yeast extract, and salts, incubated for 48 h at 28 °C. A central composite design was employed to optimize glucose and yeast extract concentrations for carotenoid and biomass production. Fermentation was carried out at 25 °C and 180 rpm for 96 h. The effects of different LED light sources (red, green, and blue) were evaluated, along with a dark control and white LED light, under optimized conditions. In addition, a 5 L stirred-tank photobioreactor was used for scale-up under blue LED illumination. The optimized medium composition—10 g/L glucose and 1 g/L yeast extract—favored carotenoid production, albeit with reduced biomass yield. Regarding light treatments, blue LED exposure resulted in the highest carotenoid production (12.3 Abs/g biomass), followed by white light (11.2 Abs/g), darkness (10.7 Abs/g), green light (10.3 Abs/g), and red light (10.2 Abs/g). In the 5 L bioreactor, carotenoid production reached 15.35 Abs/g under blue LED light, compared to 12.7 Abs/g in the dark control. Spectrophotometric analysis revealed the presence of β-carotene (451 nm), torulene (485 nm), and torularhodin (498 nm).