the key step in extraction and recovery of lipid from microalgae is cell disruption. sonication increased the efficiency of the extraction since it was partially responsible for cell disruption. the selection of the proper solvent system is still essential to the extraction process because it may weaken the cell wall structure facilitation cell disruption and therefore extraction of lipid. the addition of powder silica did not improve the extraction of oil in the cold method assisted by ultrasound. the Bligh and Dyer method assisted by ultrasound resulted in the highest extraction of oil from C. vulsaris