Study of the application of pulsed electric fields (PEF) on microalgae for the extraction of neutral lipids.

Microalgae offer a multiplicity of applications for the production of bio-sourced compounds such as proteins, pigments, sugars and oils. However, the energy spent for algae culture and lipid extraction hinder the energetic viability of the process for the production of biofuel derived from algae oils. Among possible improvements, pulsed electric fields (PEF) may be used as a pre-treatment to extract valuable compounds from microalgae and making the process less energy demanding.This project started with a collaboration between the team of bio-micro-systems Biomis, laboratory SATIE, with the team of bio-process engineering laboratory LGPM to study in situ the effects of PEF on microalgae.First, a energetic study is performed in a micro-system specially built for this project to characterize in situ, the effect of various treatment parameters (pulse duration / electric field) on Chlamydomonas reinhardtii cells with high lipid content.Among the outputs of this study, an energetic optimization of PEF conditions shows that a high level of permeability and low energy consumption are obtained when using short pulses of 5 µs. Associated with an electric field of 4.5 kV/cm, the pores are reversible (80% of the cells) during few seconds, and with a field of 7 kV/cm or higher, the permeabilization is irreversible. Afterwards, this PEFpre-treatment is associated with solvent mixing (hexane) to evaluate if lipid extraction is improved.