Carotenoids are yellow to red isoprenoid polyene pigments, widely distributed in nature, where they serve particular functions (Isler, 1971; Krinsky, 1994; Britton et al., 1995a; Frank et al., 1997). They are produced de novo by all photosynthetic organisms, including microalgae (Coodwin, 1980). Of the more than six hundred naturally occurring carotenoids structurally identified today (Straub, 1987; Britton et al., 1995a), more than one hundred different carotenoids are encountered in microalgae.