Strategies to improve the extraction and separation of carotenoids and lipids from Dunaliella salina

Dunaliella salina is a valuable industrial microalga because of its exceptional capacity to accumulate β-carotene. This study proposes a sustainable process to enhance its biotechnological potential by integrating the efficient extraction and separation of carotenoids and lipids. Conventional extraction using 15 solvents showed ethanol:hexane:water (76:18:6, with KOH), acetone:water (95:5), ethanol (96%) and ethyl acetate to be the most effective systems, all of them giving carotenoid yields greater than 83%. The saponifiable lipids (SLs) co-extracted with carotenoids using ethanol:hexane:water (76:18:6)-30% KOH were separated by SL saponification, obtaining a 93.9% recovery of the carotenoids and a 94.3% recovery of the fatty acids in two separate hexane phases. Then, acetone:water (95:5 v /v), ethanol (96%), and ethyl acetate were tested to extract carotenoid and SLs by pressurized liquid extraction (PLE) at several pressures (10 and 15 MPa), temperatures (50, 75 and 125 °C) and extraction times (3 extraction cycles of 5 and 15 min). PLE with acetone:water (95:5) at 15 MPa, 125 °C, and 3 extraction cycles of 5 min, presented the best extraction performance with 100% and 64.4% recoveries of carotenoids and SLs, respectively. Both components were separated by SL saponification for 1 h at 40 °C. Using this procedure, 87.6% of the carotenoids and 91.6% of the fatty acids were recovered over the two hexane phases. Compared to conventional extraction, PLE required ∼5 times less solvent and avoided the need for biomass pretreatment, offering a faster, cleaner, and more sustainable process for microalgal biorefineries.