Comparison of solvent extraction methods for efficient extraction of both polar and neutral lipid classes from biomass of six diverse microalgae species

Lipid extraction is critical for lipid and fatty acid analysis, yet few studies address modifications to common protocols, particularly for maximising polar lipid recovery. This study compared four solvent extraction methods for six diverse marine microalgae species (Cylindrotheca fusiformis, Tetraselmis suecica, Phaeodactylum tricornutum, Nannochloropsis oceanica, Chlorella vulgaris, and Chrysotila carterae), assessing total lipid extraction (TLE), lipid class (LC), and fatty acid (FA) profiles. Significant differences in TLE, LC, and FA composition occurred between methods for all species. Cold and hot isopropanol yielded the lowest TLE, while a hydration pre-treatment step increased TLE for some species (23.4% vs. 12.7%) but reduced it for others. No universal method bias toward specific lipid classes was observed, though within species, recovery of certain classes varied up to twofold depending on method selected. Neutral lipids dominated TLE, with appreciable quantities of glycolipids. Neutral lipid content was highest in the poorer performing methods, suggesting all extraction methods easily extract neutral lipids while less efficient ones struggled to extract polar lipid classes. Except for C. vulgaris, species contained appreciable eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with DHA highest in C. carterae and EPA abundant in C. fusiformis, P. tricornutum, and N. oceanica. Despite significant differences across all results, TLE yield was the key influence on absolute lipid class and fatty acid yield. These findings underscore the need for species-specific extraction optimization and careful consideration of solvent ratios throughout extractions to maximise recovery of target lipids or fatty acids.