Lipid Extraction from Various Species of Wet Microalgae Using Liquefied Ammonia

Abstract

Energy-intensive drying or cell-disruption processes in lipid extraction procedures reduce efficiency and increase the cost involved in producing biofuels from microalgae. Recently, a simple method was proposed for extracting lipids directly from microalgae by utilizing liquefied ammonia (NH3(l)), which eliminates the energy-intensive processes. In the present study, the versatility of NH3(l) extraction was assessed by applying it to six microalgal species with different contents of lipids. This method directly separated 25.6-70.6 wt % of the dry weight of the sample as crude extract. The total fatty acid methyl ester yield was 5.5-17.4 wt %, comparable to or exceeding that obtained by traditional approaches. The crude extract was highly enriched with valuable C12-C24 fatty acids. Furthermore, scanning electron microscopy showed that after NH3(l) extraction, the cellular structure of the residue was preserved. These results suggest that employing the NH3(l) extraction method enhances applicability and consequently increases the process value by separating components into extract and useful residual solids.