Metabolic Engineering of Chlamydomonas reinhardtii for Enhanced β-Carotene and Lutein Production

The metabolic engineering of Chlamydomonas reinhardtii , one of the fastest-growing microalgae, is a potential alternative for enhanced carotenoid productivity. CrtYB ( phytoene-β-carotene synthase – PBS ) gene from red yeast Xanthophyllomyces dendrorhous encodes for a bifunctional enzyme that harbours both phytoene synthase (psy) and lycopene cyclization (lcyb) activities. Heterologous expression of this bifunctional PBS gene led to 38% enhancement in β-carotene along with 60% increase in the lutein yields under low light conditions of 75 μmol photons m −2 s −1 . Short Duration-High Light induction strategy led to overall 72% and 83% increase in β-carotene and lutein yield reaching up to 22.8 mg g −1 and 8.9 mg g −1 , respectively. This is the first report of expression of heterologous bifunctional PBS gene resulting in simultaneous enhancement in β-carotene and lutein content in phototrophic engineered cells. Graphical Abstract