Xanthophylls are a group of C40 pigments that belong to the carotenoids family. β-Xanthophylls, such as zeaxanthin, violaxanthin and neoxanthin are derived from β-carotene metabolism, and play a central role in the protection of photo-oxidative damage in plants and algae. These molecules have interesting applications as precursors of commercially relevant natural aromas, like safranal and damascenone. Furthermore, zeaxanthin is also widely used as a nutraceutical to improve ocular health. In this study, we engineered the yeast Saccharomyces cerevisiae to biosynthesize zeaxanthin and violaxanthin from glucose. We used integrative vectors to construct a genetic stable β-xanthophylls pathway in a β-carotenogenic yeast strain. To find an effective zeaxanthin biosynthetic enzyme, we compared the titers achieved by bacterial, plant and algal β-carotene hydroxylases. Additionally, we evaluated the effect of the chloroplast transit peptide of plant and algal enzymes on zeaxanthin biosynthesis. The strain that expressed truncated version of Solanum lycopersicum β-carotene hydroxylase showed the best performance, reaching up to 4.7 mg/g DCW of zeaxanthin after 72 h cultivation in shake-flasks. Zeaxanthin producing strains were transformed with zeaxanthin epoxidase genes to further extend the pathway to violaxanthin, which was measured by UPLC-MS. To the best of our knowledge, this work presents the highest titer of zeaxanthin in S. cerevisiae reported to date, the first zeaxanthin cell factory using β-carotene hydroxylase from plants, and the first heterologous biosynthesis of violaxanthin.
Financial support of FONDECYT grant No.1170745 is greatly acknowledged. Vicente F. Cataldo acknowledges CONICYT for receiving graduate scholarship
