Assessment of milling and the green biosolvents ethyl lactate and 2-methyltetrahydrofuran (2-methyloxolane) for the ultrasound-assisted extraction of carotenoids in common and phytoene-rich Dunaliella bardawil microalgae

This study aimed to evaluate the efficiency of green solvents (ethyl lactate and 2-methyltetrahydrofuran (MeTHF)) compared to conventional solvents (ethanol, methanol, and dimethyl sulfoxide) in the ultrasound-assisted extraction of carotenoids from Dunaliella bardawil. Two types of algae were evaluated, a control (common) and a phytoene-enriched algae obtained by treatment with norfluorazon. The extractions were performed on fresh, freeze-dried, and encapsulated samples, with and without ball-milling pre-treatment. The pre-treatment had no significant effect on carotenoid extraction for any of the solvents tested. The solvents that achieved the highest carotenoid yield from fresh samples were MeTHF, methanol, and ethanol (control: 2105.3, 2001.8, and 1919.1 μg/g, respectively; phytoene-rich: 3220.9, 3669.1, and 3275.0 μg/g, respectively). In freeze-dried samples, ethanol was most effective in the control strain (14337.1 μg/g), while methanol yielded the most in the phytoene-rich strain (8464.1 μg/g). For encapsulated samples, MeTHF and ethanol were the top performers (control: 421.0 and 394.0 μg/g, respectively; phytoene-rich: 186.9 and 166.4 μg/g, respectively). Overall, the green solvent MeTHF proved to be a promising alternative to traditional solvents in the food industry.