Mixed-Polarity Azeotropic Solvents for Efficient Extraction of Lipids from Nannochloropsis Microalgae

Problem statement: The extraction of lipids from microalgae for biofuel production is a significant problem due to the intractability of their cell wall. The aim of this study of lipid extraction from Nannochloropsis microalgae was to examine the relative efficiencies of some commonly used solvent systems and test the use of co-boiling solvents in Soxhlet extraction as an improved method. Approach: We conducted a series of trials of lipid extraction from dried Nannochloropsis microalgae powder by conventional methods and compared the results to low boiling point mixed-polarity azeotropic solvent mixtures in Soxhlet extraction (a technique which has not previously been reported). Results: We found that in conventional room temperature solvent extractions, the chloroform/methanol protocols gave higher yields of lipids from Nannochloropsis than a hexane/isopropanol mixture. In testing Soxhlet extractions, we found that superior results could be obtained with hydrocarbon/alcohol azeotropic mixtures compared to hydrocarbon only solvents (i.e., hexane, cyclohexane), especially with a cyclohexane/butanol (9:1 ratio) mixture. Conclusion: The latter results indicate the potential for performing efficient microalgae lipid extractions with nonhalogenated solvent systems in the future (a greener alternative).