Tertiary amine as an efficient CO₂ switchable solvent for extracting lipids from hypersaline microalgae

Considering the momentous cost drivers in energy efficient algal biorefinery processes, a green alternative in extracting lipid from microalgae is anticipated. Switchable solvent system using tertiary amines namely DMBA (Dimethylbenzylamine), DMCHA (Dimethylcyclohexylamine), and DIPEA (Diisopropylethylamine) for lipid extraction from wet hypersaline microalgae was investigated in this study. Interestingly, present study showed that at 1:1 (v/v of fresh DMBA solvent: microalgal biomass), and for 1 h extraction time, the lipid yield was 41.9, 26.6, and 33.3% for Chlorella sp. NITT 05, Chlorella sp. NITT 02, and Picochlorum sp. NITT 04, respectively and for recovered DMBA solvent, at 1:1 (v/v) and for 1 h extraction time, the lipid yield was 40.8, 25.97, and 32%, respectively. Similarly, lipid extraction using DMCHA solvent for Chlorella sp. NITT 05, Chlorella sp. NITT 02, and Picochlorum sp. NITT 04 at 1:1 (v/v of solvent: microalgal biomass) and 1 h extraction time showed 34.28, 24.24 and 23.33% lipids, respectively for fresh solvent and 34.01, 24.24 and 23.18% for recovered solvent respectively; while DIPEA was not competent in lipid extraction from three tested microalgae. FAME profile revealed the presence of saturated fatty acids as 43.04%, 40.98%, 38.45% and monounsaturated fatty acids as 28.38%, 27.05%, 23.3% for Chlorella sp. NITT05, Picochlorum sp. NITT04, Chlorella sp. NITT02, respectively. This study attributes Chlorella sp. NITT05 and Picochlorum sp. NITT04 to be ideal algal species for biodiesel production.