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.