Green Pretreatment Using Deep Eutectic Solvents to Enhance Lipid Recovery from Chlorella vulgaris

Abstract

Biodiesel from microalgae is considered a promising renewable fuel, but the thick cell wall of Chlorella vulgaris makes lipid recovery difficult. This research used green deep eutectic solvents (DESs) as a pretreatment to improve the lipid extraction performance. Two choline chloride-based DESs, namely choline chloride–acetic acid (CCA) and choline chloride–urea (CCU), were tested at several concentrations before the biomass was extracted using ultrasound-assisted extraction with the Folch solvent system (chloroform:methanol, 2:1 v/v). Lipid content was determined using the sulphophosphovanillin (SPV) method. The result showed that both DESs increased lipid recovery compared to extraction without pretreatment, although the performance was strongly affected by the solvent composition. The highest lipid yield for CCA was obtained at 85% concentration, which was 2,105.18 µL, or 36.1% higher than the control (1,546.47 µL). Meanwhile, 70% CCU gave the best result of 3,516.10 µL, an increase of 127.4% compared to the untreated biomass. This increase in extraction efficiency was caused by the disruption of the microalgal cell wall through hydrogen-bond interactions and better solvent penetration during ultrasonic cavitation. From the comparison, CCU-based DES was more effective than CCA under the tested conditions, showing that CCU is more suitable as a green pretreatment for lipid recovery from Chlorella vulgaris.