Ultrasound-assisted pretreatment using ternary deep eutectic solvent and lipid extraction from Nannochloropsis oceanica.

Nannochloropsis sp. contains high levels of polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA). There is a need to establish highly efficient extraction processes to replace traditional organic solvents. First, the optimal DES system Choline chloride:1,4-butanediol:lactic acid = 1:2:1 was selected for Nannochloropsis oceanica. Response surface methodology optimized pretreatment conditions to 73% ultrasonic power (876 W), 17 min duration, and a 1:22 g/g solid-to-liquid ratio. Subsequently, the optimal methanol/hexane ratio was 1:3 v/v and the optimal extraction time was 15 min for the lipid extraction process. The final lipid yield reached 281.67 ± 7.10 mg/g, representing a 24.65% increase over the control (without the pretreatment), with a lipid recovery efficiency of 95.53 ± 2.41%. Density functional theory confirmed its mechanism of enhancing extraction efficiency by disrupting cell wall structures. This study established a novel process for extracting lipids from N. oceanica using a deep eutectic solvent via ultrasound-assisted cell wall disruption followed by ultrasound-assisted extraction.