Pulsed Electric Field for protein release from microalgae

Recently the cultivation and refinery of microalgae biomass has stimulated intensive research due to its relative high content of more than 50% of valuable cell components, like proteins, lipids, polysaccharides, and pigments. Besides, the areal productivity is much higher compared to other agricultural plants. The aim of this STSM was to explore the possibilities to use Pulsed Electric Field (PEF) for extraction of water soluble proteins from microalgae. The microalgae Chlorella vulgaris was cultivated in a 12 L photobioreactor at Wageningen University in Netherlands under both nitrogen replete (N+) and nitrogen deplete (N-) conditions. By means of centrifugation the algal harvest was concentrated and then stabilized as freeze dried. At ProdAl Scarl, Fisciano, Italy the microalgal suspensions were prepared at 25 g/L for both the N+ and N- algae by resuspending the freeze dried material in tap water and rehydrated at 4 °C overnight. Five PEF experiments were performed at different field strengths (20 and 30 kV/cm) and specific energy consumptions (50 and 100 kJ/kg) on both the N+ and N- biomass. The water soluble protein concentration in the supernatant was measured. Unfortunately, the freeze drying caused the cells to break, releasing the water soluble proteins in the supernatant after resuspension. Therefore no significant increase of protein was obtained after PEF. This leads to the conclusion that PEF can only be performed on fresh biomass.