Preliminary study on lipid extraction from Nannochloropsis salina using supercritical carbon dioxide method

Abstract

The issues involved with conventional lipid extraction methods, such as the usage of toxic solvents and accumulation of chemical waste, has motivated researchers to find an alternative approach to the extraction technology. One of the alternatives is via the Supercritical Carbon Dioxide (SC-CO₂) method. This extraction method is considered as green as it provides a clean, selective and efficient process. Although the SC-CO₂  method has been successfully used to extract lipids from microalgae, there are still some issues related to sample preparation and process parameters that need to be resolved. Therefore, this study investigates the effect of adding a modifier (ethanol) and using different types of holders (cotton and steam bun cloth) has on the yield of lipid from Nannochloropsis salina. The usage of a holder is required during the process due to the fine particles of the microalgae which have the potential to clog the instrument used. The SC-CO₂ extraction without the modifier was conducted for 4 hours at 60°C, 30 MPa and CO₂ flow rate of 4 ml/min, while the extraction with the modifier was conducted using 3.8 ml/min CO₂ and 0.2 ml/min ethanol. It was found that the highest lipid yield of 0.16 g lipid / g dried microalgae was achieved using cotton cloth as a holder with the addition of the modifier. Lower amount of lipids were obtained when using the Soxhlet method (0.08 g lipid / g dried microalgae) and SC-CO₂ without modification (0.02 g lipid / g dried microalgae). These preliminary findings show that the SC-CO₂ process requires modifications to enhance the lipids yield from microalgae.