A Microfluidic Device for the Real-Time Characterization of Lipid Producing Algae Cell Population Submitted to a Pulsed Electric Field

Thanks to their high fatty acids content when cultivated in stress conditions (high light, no nitrogen), algae are considered as a renewable source of lipid-rich biomass feedstock for biofuels. The application of Pulsed Electric Field (PEF) to electroporate the algae, is a promising alternative to the use of solvents for lipid droplets extraction from these cells. In order to study the effects of PEF applied to oleaginous algae cells, we developed a microfluidic device, allowing real time visualization. Multiple closed electroporation chambers are designed on this biochip to characterize in real-time Propidium Iodide penetration on a population of algae, submitted to the PEF, and confined within each chamber. The method developed allows (1) to find the permeabilization threshold considering the treatment parameters (pulse width, amplitude and frequency) varying electric field, (2) to distinguish cell sensitivity in different conditions of growth, or different cell strains. Lipid droplets visualization in fluorescence and bright field during treatment was also performed on the device. We investigated the effects of PEF on the possible displacement or merging of droplets within the cytoplasm. While optimized electroporation parameters could be found for the different algae strains with different lipid content that we investigated, the possible extraction of lipids remains challenging and strain dependent, due to the cellulosic cell wall.