Microalgae lipid extraction using tertiary amine switchable hydrophilicity solvents DMCHA and DIPA

A limited number of studies have investigated microalgae lipid extraction using Switchable Hydrophilicity Solvents (SHS), despite this they have demonstrated high lipid recoveries. This is the first study to investigate the lipid extraction of both eukaryotic and prokaryotic microalgae using N, N-Dimethyl cyclohexylamine (DMCHA) and N, N-Diisopropyl ethanolamine (DIPA). SHS possess the unique ability to reversibly change their hydrophilicity when exposed to an inducer such as CO₂, N₂, or Argon through a protonation reaction. Five microalgae species were selected for investigation, namely, Botryococcus braunii UTEX 2441, Botryococcus braunii sp., wild Scottish Blue-Green cyanobacteria, Chlorella vulgaris, and Haematococcus pluvialis using the tertiary amines DMCHA and DIPA, with hexane being used as a baseline control. The study has shown DMCHA and DIPA to be efficient solvents for lipid extraction when compared to hexane. DMCHA achieved the highest lipid extraction yields of 56.10 wt% ± 6.66 with B. braunii UTEX 2441 and 45.66 wt% ± 1.68 with C. vulgaris which is a 17.87 and 17.70 wt% increase compared with hexane respectively. DIPA showed a 9.39 wt% increase in lipid yield recovery compared with hexane for Blue-Green cyanobacteria. H. pluvilais was the only species not to achieve higher lipid extraction yields with SHS.