Microwave assisted lipid extraction from microalgae using biodiesel as co-solvent

This study reports the solvent potential of biodiesel (methyl soyate) for microalgal lipid extraction while employing microwave-assisted extraction (MAE). Two co-solvent systems, BD20 and BD40 containing 20% and 40% of biodiesel in ethanol respectively, were experimented at 80 °C, 100 °C, and 120 °C in MAE. Results were compared to those of the MAE using chloroform and ethanol (1:2) as well as conventional 8 h Soxhlet extraction. Results indicated that approximately 66% and 78% of the oil within the cells were extracted with BD40 at 80 °C and 100 °C, respectively. Increase in temperature to 120 °C increased the efficiency of BD40 extraction to 115.5%, relative to conventional Soxhlet extraction. The BD20 co-solvent on the other hand extracted 27%, 34%, and 24% of oil at 80 °C, 100 °C, and 120 °C temperatures respectively. MAE using chloroform and ethanol showed 32%, 93%, and 108% of oil compared to Soxhlet. Data indicated that increase in biodiesel proportion in the co-solvent and increased temperature lead to more efficient extraction. Scanning electron microscope (SEM) images were used to discern the cell structures before and after the extraction. This study was aimed at identifying benign alternatives for the traditional toxic solvents like n-hexane for extracting microalgal lipids.