Bicarbonate and nitrogen starvation: A dynamic duo for canthaxanthin accumulation in Chlorella saccharophila

This study investigates the impact of bicarbonate supplementation and nitrogen starvation on canthaxanthin production in Chlorella saccharophila UTEX247. A two-stage cultivation strategy was employed to optimize canthaxanthin production. The first stage focused on biomass enhancement through bicarbonate supplementation, achieving 1.3 g L⁻¹ biomass. The second stage induced canthaxanthin accumulation under nitrogen starvation, resulting in an approximately eightfold increase in canthaxanthin content (594.18 ± 62.14 µg g⁻¹ dry weight). Transcriptomic analysis revealed the upregulation of key genes involved in canthaxanthin biosynthesis, such as BKT and DXPS, and the downregulation of lutein pathway genes, suggesting a metabolic shift towards canthaxanthin production. The study highlights the potential of the two-stage cultivation strategy and identified key genetic targets for further enhancing canthaxanthin production in microalgae, contributing to the development of sustainable microalgal biorefineries.