Green ultrasonication-assisted extraction of microalgae Chlorella sp. for polysaturated fatty acid (PUFA) rich lipid extract using alternative solvent mixture

Conventionally, microalgal lipid extraction uses volatile organic compounds as an extraction solvent. However, these solvents are harmful to human and environmental health. Therefore, this study evaluated the feasibility of alternative green solvents, namely, ethanol, dimethyl carbonate (DMC), cyclopentyl methyl ether (CPME), and 2-methyltetrahydrofuran (2-MeTHF) in lipid extraction from Chlorella sp. via ultrasound-assisted extraction (UAE). This study indicated that extraction parameters, such as ethanol-to-2-MeTHF ratio, solvent-to-biomass ratio, temperature, and time, significantly affected the crude lipid yield (P < 0.05). The highest crude lipid yield of 25.05 ± 0.924% was achieved using ethanol-2-MeTHF mixture (2:1, v/v) with a solvent-to-biomass ratio of 20:1 (v/w) at 60 °C for 25 min accompanying 100 W and 40 kHz. Ethanol-2-MeTHF-extracted lipids showed dominance in linoleic acid, α-linolenic acid, and palmitic acid. Overall this findings supported UAE using ethanol and 2-MeTHF as extraction solvents is a promising green alternative to conventional solvent extraction of lipids from microalgae.