Microalgae are an attractive source for biofuels due to their high growth
rates and lipid content. However, up to the present time, the extraction of lipids from
wet microalgae biomass remains an energy-intensive step, and an impediment for the
economically viable large scale bio-oil production. During the extraction process, cell
disruption and drying are two of the most energy-consuming steps. Several studies on
genetic modification of microalgae towards lipid accumulation enhancement, or to
reduce the harvesting and lipid extraction cost have been carried out successfully. This
chapter aims to summarize the recent developments in microalgal oil extraction
processes, including drying methods, cell disruption methods, conventional or
supercritical solvent extraction methods, and recent approaches for direct biodiesel
production. The current developments in metabolic engineering for lipids production
are also reviewed. Hydrothermal liquefaction is also included as an alternative route to
convert wet biomass into bio-crude oil.
Keywords: Biofuel, Cell disruption, Extraction, Genetic engineering,
Hydrothermal liquefaction, Lipids, Microalgae.
