Synergistic effects of light irradiation and 1‐aminocyclopropane‐1‐carboxylic acid on the enhanced carotenoid accumulation in <scp> <i>Dunaliella sp.</i> FACHB </scp> ‐847

Abstract BACKGROUND The microalga Dunaliella sp. FACHB‐847 is known for its ability to accumulate high levels of lutein, making it a promising source of natural carotenoids. To enhance its suitability for industrial‐scale production, various strategies have been explored to boost carotenoid yields. In this study, 1‐aminocyclopropane‐1‐carboxylic acid (ACC), a precursor of ethylene, was exogenously applied to promote carotenoid accumulation in Dunaliella sp. FACHB‐847. RESULTS Exogenous ACC application (15 mM) stimulated algal growth, with biomass reaching 1.70 g L −1 , and increased the chlorophyll content (chlorophyll a and b ) to 29.51 mg L −1 , resulting in a 1.37‐fold increase compared to the control. High lutein productivity (4.19 mg g −1 ) was achieved under 15 mM ACC treatment, representing a 0.68‐fold increase compared to the control. Upregulated expression of key genes in the carotenoid biosynthesis pathway, including lycopene β‐cyclase, lycopene ε‐cyclase , and β‐carotene hydroxylase under ACC treatment contributed to the promoted carotenoid accumulation. Furthermore, the combination of ACC with high photon flux density (180 μmol m −2 s −1 ) synergistically enhanced both biomass production and pigment synthesis. Notably, even under low photon flux density (72 μmol m −2 s −1 ), ACC‐treated cultures accumulated higher carotenoid levels than those of the high‐light control group. CONCLUSION These results indicate a synergistic effect between ACC and light irradiation. The findings suggest that relatively low light conditions, combined with ACC treatment, can achieve high carotenoid productivity, thereby offering a potential reduction in energy costs associated with illumination. © 2025 Society of Chemical Industry (SCI).