QUANTITATIVE DETERMINATION OF THE CAROTENOIDS IN YEASTS OF THE GENUS RHODOTORULA

Abstract

Methods have been developed for the characterization and quantitative analysis of carotenoids present in species of the genus Rhodotorula. The pigments in hexane, obtained from cells grown and extracted as reported previously, were extracted with 90% methanolic potash (0.1 [image]) and the alkali-soluble torularhodin determined by the difference in absorption of the hexane solution at 500 mu, before and after extraction. Aliquots of the extracted hexane were then chromatographed on columns of MgO-Supercel (21) and developed with 95% ethanol. Beta-carotene and Gamma-carotene were eluted completely with the ethanol and their respective concentrations determined from readings at critical wave lengths using formulae customarily used for the colorimetric analysis of two-component color systems. The strongly adsorbed torulene was determined from the difference in absorption at 484 m[mu], before and after chromatography. The relative quantities of torularhodin, torulene, Beta-carotene and Gamma-carotene, respectively in each of four Rhodotorula species were as follows (in percent of total pigment) R. gultinis: 66.8, 27.2, 3.5, and 2.3; R. glutinis var. rubescens: 29.8, 37.8, 23.9, and 8.5; R. rubra: 49.3, 27.5, 14.6, and 8.5; and R. mucilaginosa: 28.6, 59.3, 9.0, and 3.1. Mean yields of total pigment from the four species were (in mcg. per gram of dry cells): R. glutinis 332; R. glutinis var. rubescens 494; R. rubra 187; and R. mucilaginosa 358.