Influence of Pulsed Electric Field (PEF) treatment on the extraction of lipids from the microalgae Auxenochlorella protothecoides

Summary form only given. Microalgae are a promising source of lipids and biopolymers. In most cases algal lipids are stored intracellular. During the extraction of intracellular products from cells the cell wall and the cell membrane are natural barriers, preserving the cell content. Pulsed Electric Field (PEF) treatment results in the electroporation (EP) or the electropermeabilization of the cell membrane. The formation of pores across the membrane often leads to an enhanced extraction process since solvents can penetrate the biomass matrix more efficiently. In this study the influence of PEF treatment on the extraction of lipids from the microalgae Auxenochlorella protothecoides. was investigated. Microalgae suspensions with a cell density of 50-100 g/1 (dry mass) and a lipid content of the algae of 15-20% (by weight) were treated in a flow cell connected to a transmission line pulse generator. Pulses of 1 μs were applied at a constant specific energy input. After PEF-treatment the microalgae were removed immediately from the suspension by centrifugation. The algae-pellet was dried before a solid liquid extraction was performed using ethanol as organic solvent. In order to investigate the spontaneous release of intracellular compounds the supernatant was analyzed using High-Performance Liquid Chromatography (HPLC). Compared to the control samples the Dissolved Organic Carbon Content (DOC) of the supernatant was up to 4 times higher after PEF-treatment. However the HPLC-analysis revealed that hardly any high molecular weight compounds and no hydrophobic substances, e.g. lipids, did leak out of the cells. The increase in DOC primarily was due to low molecular weight compounds, presumably monosaccharides and amino acids. The solid-liquid extraction experiments showed that the lipid-recovery from PEF treated microalgae was considerably higher compared to untreated cells. Although the EP did not lead to a spontaneous release of intracellular lipids into the surrounding liquid, it resulted in an improved lipid extraction from dehydrated microalgae.