Method for Torularhodin Separation and Analysis in the Yeast Rhodotorula Rubra Aerobically Cultivated in Lab Bioreactor

摘要

The paper presents a procedure realized for the extraction, separation, and quantitative determination of the carotenoids, mainly beta-carotene and torularhodin, with antioxidant possible application, from the yeast Rhodotorula rubra ICCF 209. The procedure was applied after the aerobic bioprocess completion. Wet biomass was separated by centrifugation at 8000 rpm and the total carotenoid pigments was carried out by extraction with acetone-water and n-hexane, with all carotenoid pigments in the upper hexane layer. The pigmented hexane layer was then washed with distilled water. The optical density of the pigmented hexane filtrate was determined on a UV-VIS spectrophotometer (Jenway Spectrophotometer) at 500 nm against a hexane blank to give the total pigment concentration. The pigment torularhodin was separated from the hexane by extraction with methanol potash (0.1 N) and the visible spectrum at 380-700 nm was drawn to obtain the torularhodin concentration. A final concentration of the total carotenoids as beta-carotene of 250-450 μg/L medium and a concentration of torularhodin of 140-350 μg/L was determined in case of the aerobic bioprocess in the 3.7 L Bioengineering AG lab bioreactor with mechanical stirring with a duration of 72 hours. In the first 24 hours the beta-carotene was the major component of carotenoids, while after 48 hours it seems that more than 50% of this pigment is transformed into torularhodin via the metabolic pathway described in the literature.