Electric Pulse Pretreatment for Enhanced Lipid Recovery from Chlorella protothecoides

Developing effective, energy-efficient methods to extract lipids from microalgae remains a challenge in bioenergy. This study assesses electric pulse (EP) pretreatments to enhance lipid extraction from Chlorella protothecoides. In tandem with solvent extraction, we applied 10, 50, 100, 200, and 300 60 kV/cm, 60 ns duration EPs or 3, 17, 33, 67, and 100 60 kV/cm, 300 ns duration EPs to match the energy density u applied to the sample for each EP duration. Lipid recovery increased with increasing u for each EP duration until reaching a maximum for 17 300 ns EPs (the second lowest u) and 100 60 ns EPs (the third lowest u) to achieve a 13.3% and 16.1% increase in lipid extraction, respectively. Lipid extraction declined at higher u due to increased cell lysis. The largest net energy released calculated from the difference between the energy available from the extracted lipids and the applied energy of the EPs occurred at the lowest u for each EP duration. Applying trains of 100 μs EPs induced qualitatively similar behavior. These results suggest that a more detailed parametric study may optimize EP parameters for net energy release for specific microalgae and solvents.