Abstract
The red yeast Xanthophyllomyces dendrorhous is an established platform for the synthesis of carotenoids. It was used for the generation of novel multi oxygenated carotenoid structures. This was achieved by a combinatorial approach starting with the selection of a β-carotene accumulating mutant, stepwise pathway engineering by integration of three microbial genes into the genome and finally the chemical reduction of the resulting 4,4'-diketo-nostoxanthin (2,3,2',3'-tetrahydroxy-4,4'-diketo-β-carotene) and 4-keto-nostoxanthin (2,3,2',3'-tetrahydroxy-4-monoketo-β-carotene). Both keto carotenoids and the resulting 4,4'-dihydroxy-nostoxanthin (2,3,4,2',3',4'-hexahydroxy-β-carotene) and 4-hydroxy-nostoxanthin (2,3,4,2'3'-pentahydroxy-β-carotene) were separated by high-performance liquid chromatography (HPLC) and analyzed by mass spectrometry. Their molecular masses and fragmentation patterns allowed the unequivocal identification of all four carotenoids.