Ultrasound assisted extraction of Nannochloropsis: Effects on lipid extraction efficiency and lipid stability

Abstract

Ultrasound assisted extraction of microalgal lipids from Nannochloropsis in presence of hexane/isopropanol extraction solvent was studied. The results were compared with adequate control extractions, using the same solvent system, solvent contact time and extraction temperature but in the absence of ultrasound. Ultrasound assisted extraction at 0.45 W/mL and control extractions at elevated temperatures (comparable to the temperature induced by the ultrasound) resulted in similar lipid, free fatty acid and pigment extraction efficiencies and the free fatty acid and pigment content of the lipid extracts was comparable. The control and ultrasound assisted extractions did not influence the lipolytic and oxidative stability of the lipids during extraction. These results indicated that the positive impact of ultrasound assisted extraction can almost completely be attributed to the ultrasound induced increased temperature. Simpler extraction techniques applying moderate heating (± 40 °C) in presence of lipid extraction solvents are most probably more straightforward to implement industrially compared to ultrasound assisted extraction.