The effect of solvents polarity and extraction conditions on the microalgal lipids yield, fatty acids profile, and biodiesel properties

[Display omitted] •The effect of polar and non-polar solvents on microalgal biodiesel was investigated.•The amount of extracted lipids by non-polar solvents was higher than polar solvents.•A higher amount of saturated fatty acids was obtained by non-polar solvents.•The cetane number was higher for the extracted lipids by non-polar solvents.•Reaction temperature affected the saturation degree of fatty acids. This study reports the effects of polar (acetone/methanol) and non-polar (chloroform/hexane) solvents on lipid yield, fatty acids methyl esters (FAMEs) composition, and biodiesel properties of microalgae. The lipids yield extracted by hexane and chloroform (100.01 and 94.33 mg/g) were higher than by methanol and acetone (40.12 and 86.91 mg/g). The polarity of solvents also affected FAMEs composition of microalgal lipids. Total saturated fatty acids and unsaturated fatty acids of extracted lipids were 61.53% and 38.47% by chloroform and 38.85% and 61.15% by methanol. Moreover, polar and non-polar solvents affected the biodiesel properties such as cetane number and oxidative stability. In addition, higher ratio of chloroform to methanol and higher temperature increased the lipid yield and saturation degree of lipids, through ultrasound-assisted lipid extraction method. Overall, the results revealed that the lipids yield, FAMEs composition, and biodiesel quality of microalgal biomass can be significantly affected by solvents polarity and extraction conditions.