NOVELTY - Isolating oil from microorganisms in aqueous media comprises: (a) adding pressurized carbon dioxide (CO2) as a solute to the media containing the microorganisms, where CO2 is dissolved in the media resulting in an oil rich phase; and (b) removing the oil phase, thus isolating the oil from the microorganism.    USE - The methods are useful for isolating oil from microorganisms in aqueous media; harvesting whole cell microorganisms from aqueous culture medium; obtaining oil from oil that is secreted or released from whole cell microorganisms in aqueous culture medium; and for using CO2 or CO2 and oil mixture in contact with aqueous solution of intact cells. The lipid is used for biofuel production (all claimed).    ADVANTAGE - The invention provides CO2 solute technology that alters the physical properties (viscosity, density, solubility) of algal lipids (oils) in order to facilitate their purification from water and algal biomass. The technology is environment-friendly using readily available CO2 that is recaptured and recycled and, most importantly, less costly than current methods. The method is an integrated and scalable process for CO2 solute enhanced lipid isolation from aqueous microorganisms that has been demonstrated at the laboratory scale.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a method for harvesting whole cell microorganisms from aqueous culture medium comprising: (a) adding pressurized CO2 to the whole cells, where CO2 is a solute that is dissolved by the cells thus increasing the buoyancy of the cells; and (b) isolating the cells;    (2) a method for obtaining oil from oil that is secreted or released from whole cell microorganisms in aqueous culture medium comprising: (a) adding pressurized CO2 to the whole cells, where CO2 is a solute that is dissolved by the cells thus increasing the buoyancy of the cells; (b) isolating the cells; (c) subjecting the cells to rapid decompression thus rupturing the cells to obtain a biomass phase, a water phase, and an oil phase; and (d) removing the oil phase, thus isolating the oil from the microorganism;    (3) a method of using CO2 or CO2 and oil mixture in contact with an aqueous solution of intact cells, where the CO2 or the CO2 and oil mixture extracts or partially extracts oil from the intact cells; and    (4) oil obtained by the method.