Pulsed electric field assisted extraction of intracellular valuables from microalgae

This paper discusses the application of pulse electric field (PEF) treatment for the cell disintegration of the fresh water microalgae Auxenochlorella protothecoides. The algae were cultivated under controlled conditions in a closed photo-bioreactor. After algae harvest the algae suspensions were concentrated and PEF treated with square pulses with a duration of 1 μs. We investigated the influence of specific treatment energy (52-211 kJ/kg suspension), electric field strength (23-43 kV/cm) and biomass concentration (36-167 g dry weight per kg suspension) on cell disintegration. For all pulse parameters applied, the PEF induced cell disintegration resulted in the release of soluble intracellular matter into the suspension. The disintegration efficiency increased with increasing specific treatment energy, whereas the field strength hardly had any influence. For suspensions with a biomass content of 100 g dry weight per kg suspension the electrical energy input necessary for considerable cell rupture was in the range of 1 MJ/kg dried algae. This is equivalent to 4.8% of the upper heating value of the algae. Although the treated algae contained lipids, PEF treatment only led to the spontaneous release of soluble components. The selectiveness of the process might offer the opportunity to use PEF treatment in a biorefinery concept, where soluble algae ingredients are extracted before solvent extraction of lipids is performed.