Techniques of lipid extraction from microalgae for biofuel production: a review

Microalgae are feedstocks for production of carbon-neutral biofuels. Efforts have been performed to market microalgae biofuels, yet the production of microalgae biofuel remains a challenge due to the high production cost and low product yield. In particular, lipid extraction is a critical step to be optimized. Here, we review lipid extraction technologies and cell lysis strategies. Extraction techniques involve solvents such as organic solvents, supercritical fluids, ionic liquids, deep eutectic solvents and switchable solvents. Advantages and shortcomings of solvents are discussed. Besides, strategies have been designed to reduce power costs by integration of unit operations in downstream processing. We present single-step processes for simultaneous cell lysis and lipid extraction, such as ultrasound-, microwave-, bead-beating-, surfactant- and pulsed electric field-assisted extractions. The lipid extraction yield is enhanced by incorporating cell disruption into the lipid extraction process.