Isolation and Characterization of Carotenoid-rich Lipid Globules from Peridinium foliaceum

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Abstract
Carotenoid-rich oil globules were isolated from the cytoplasm of the binucleate dinoflagellate, P. foliaceum. These orange globules were collected from ruptured cells by ultracentrifugation on a sucrose density gradient, and checked for purity by EM. The osmiophilic globules were assayed for lipid (including pigment) and protein content. The lipid to protein ratio was 1.39:1, with a calculated density of the globules of 1.05 g/cm3. The lipids were composed of hydrocarbon, wax ester (phytyl ester), triglyceride and polar (no phospholipid) fractions. The biochemical composition indicated that the globules function as a reservoir of energy-rich components in the cell. Microspectrophotometric observations were consistent with pigment analyses which demonstrated that the globules were carotenoid-rich. In addition to .beta.-carotene, .gamma.-carotene and canthaxanthin, the carotenogenic precursors: phytoene, phytofluene, .zeta.-carotene and .beta.-zeacarotene were isolated from the globules. Corrected fluorescence maxima of phytoene and phytofluene in hexane were recorded at 340 and 490 nm, respectively. Carotenes constituted 3.3% of the total oil globule lipid. The possibility of an extraplastidic carotenogenic enzyme system in P. foliaceum is discussed.