Quantification of carotenoids in cells of Phaffia rhodozyma by autofluorescence

The distribution and intensity of autofluorescence caused by carotenoids in the yeast Phaffia rhodozyma was examined by laser confocal fluorescence mi croscopy. Carotenoid contents of individual yeast cells could be calculated from the value of autofluorescence/unit volume of yeast cell. The average level of fluorescence in highly fluorescing yeast cells was 15 mg carotenoi d g(-1) yeast which was accepted as the maximum yield of carotenoid in P. r hodozyma. The method developed in this study is useful for the research of cell biology associated with the biological functions of carotenoids in ind ividual cells.