Efficacy of extraction techniques and solvent polarity on lipid recovery from domestic wastewater microalgae

Abstract

Wastewater algae are very interesting biomaterial as a sustainable feedstock for biodiesel generation. The objective of this study is to investigate the quality and quantity of oil from algal biomass sampled from the domestic wastewater treatment plant located in Beni-suef governorate, Egypt. For this, two mixed cultures were harvested, one of the two mixed cultures was dominated by Spirulina maxima, while the other by Euglena sanguinea. The effectiveness of three extraction techniques (conventional, ultra-sonication and microwave) on the lipid yield and fatty acid profile were investigated. The algal lipid was tested quantitatively and qualitatively using six solvent systems (hexane: isopropanol (3:2), hexane: ethanol (1:1), chloroform: methanol (1:1), diethyl ether, ethanol, and methanol) to select the most effective solvent. Microwave extracted the highest lipid percentage from S. maxima with ethanol (43.8%) while E. sanguinea (36.3%) with methanol. The algal cells morphology using Scanning Electron Microscope (SEM) cleared that cells after microwave were more severe damage compared to other methods. Gas Chromatography (GC) analysis was done to identify and quantify the fatty acid of two mixed cultures, under various extraction techniques and solvent systems. The results showed that algae grown on wastewater are considered as an attention source of low-cost lipid for high-quality biodiesel.