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Carotenoids are organic lipophilic yellow to orange and reddish pigments of terpenoid nature that are usually composed of eight isoprene units. This group of secondary metabolites includes carotenes and xanthophylls, which can be naturally obtained from photosynthetic organisms, some fungi, and bacteria. One of the microorganisms able to synthesise carotenoids is the heterobasidiomycetous yeast Xanthophyllomyces dendrorhous, which represents the teleomorphic state of Phaffia rhodozyma, and is mainly used for the production of the xanthophyll astaxanthin. Upgraded knowledge on the biosynthetic pathway of the main carotenoids synthesised by X. dendrorhous, the biotechnology-based improvement of astaxanthin production, as well as the current omics approaches available in this yeast are reviewed in depth.

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Transcription of the pcbAB, pc6C and penDE genes of Penicilliurn chrysogenum AS-P-78 is repressed by glucose and the repression is not reversed by alkaline pHs Glucose repressed transcription of the penicillin biosynthesis genes pcbAB, pcbC and penDE when added a t inoculation time to cultures of Penici//ium chrysogenum AS-P-78 but it had little repressive effect when added a t 12 h and no effect when added a t 24 or 36 h. A slight increase in the expression of pcbC and penDE (and to a smaller extent of pcbAB) was observed in glucose-grown cultures a t pH 68,7-4 and 8 0 as compared with pH 62, but alkaline pHs did not override the strong repression exerted by glucose. Transcription of the actin gene used as control was not significantly affected by glucose or alkaline pHs. Repression by glucose of the three penicillin biosynthetic genes was also observed using the lacZ reporter gene coupled to each of the three promoters in monocopy transformants with the constructions integrated a t the pyrG locus. Glucose repression of the three genes encoding enzymes of penicillin biosynthesis therefore appears to be exerted by a regulatory mechanism independent from pH regulation.