Variation in the fatty acid composition of microalgal lipids due to the effect of the extraction method

Abstract

Lipid extraction from microalgae was studied more specifically considering the effects of the extraction method and solvent mixture on cell walls. Chlorella vulgaris and Nannochloropsis oculata were maintained in Bold Basal Medium (BBM) and, Dunaliella salina and Dunaliella tertiolecta in Guillard "F/2" medium, sterile with continuous aeration at 18 ºC at 80 µmol photons m−2 s−1. The objective of the study was to evaluate and compare the lipid content and fatty acid profiles of 4 microalgae species (freshwater and marine species) using two lipid extraction methods, Soxhlet and ultrasonication. Biomass production was greatest in the stationary phase for all microalgae, with D. salina exhibiting the highest production with 0.40–0.42 g L−1. Biomass productivity for freshwater microalgae was higher in the stationary phase (0.0360–0.0407 g L−1 day−1) and in the exponential phase for marine microalgae (0.057–0.064 g L−1 day−1). The highest percentage of lipids in marine microalgae was between 38–54% by weight in the stationary phase, with D. tertiolecta; in comparison, the freshwater microalgae reached between 22–23% by weight in the exponential phase, for the species N. oculata. The highest number of fatty acids observed in marine microalgae was by Soxhlet extraction in D. tertiolecta in both growth phases. The highest percentage of any fatty acid with this method was palmitic acid (61%) in the stationary phase of C vulgaris. The ultrasonication extraction method presented the highest percentages in the stationary phase of N. oculata and D. tertiolecta, palmitic acid (C16:0) showing the highest percentages (87 and 51%) in the exponential phase in both marine microalgae. In short, it was observed that the extraction method and solvent mixture could influence fatty acid profile.