Abstract

Carotenoids are naturally produced by plants, algae, and some bacteria and fungi, fulfilling functions as accessory photosynthetic pigments and antioxidants. Among carotenoids, the xanthophyll astaxanthin stands out for its antioxidant and nutraceutical properties, which are beneficial to human health, and also for its use in the aquaculture industry as nutritional supplement of salmonid fish. Many studies have focused on the search of natural sources of astaxanthin as an alternative production that guarantees the beneficial properties of this compound. In nature, few astaxanthin-producing organisms are known, being the microalgae Haematococcus pluvialis and the yeast Xanthophyllomyces dendrorhous the most promising microbiological systems for the biotechnological production of this carotenoid. In this chapter, we describe the carotenogenic pathways in these microorganisms and the proposed carotenogenesis regulation mechanisms. As an example, the influence of the carbon source, the regulation by catabolic repression and by sterols in the carotenogenesis in the yeast X. dendrorhous is described.