Application of pulsed electric fields for the biocompatible extraction of proteins from the microalga Haematococcus pluvialis

This study aims to employ a pulsed electric field (PEF) treatment for the biocompatible (non-destructive) extraction of proteins from living cells of the green microalga Haematococcus pluvialis. Using a field strength of 1 kV cm-1, we achieved the extraction of 10.2 µg protein per mL of culture , which corresponded to 46% of the total amount of proteins that could be extracted by complete destructive extraction (i.e. the grinding of biomass with glass beads). We found that the extraction yield was not improved by stronger field strengths and was not dependent on the pulse frequency. A biocompatibility index (BI) was defined as the relative abundance of cells that remained alive after the PEF treatment. This index relied on measurements of several physiological parameters after a PEF treatment. This way found that at 1 kV cm-1 that cultures recovered after 72 h. Therefore, these PEF conditions constituted a good compromise between protein extraction efficiency and culture survival. To characterize the PEF treatment further at a molecular level, mass spectrometry-based proteomics analyses of PEF-prepared extracts was used. This led to the identification of 52 electro-extracted proteins. Of these, only 16 proteins were identified when proteins were extracted with PEF at 0.5 cm-1. They belong to core metabolism, stress response and cell movement. Unassigned proteins were also extracted. Their physiological implications and possible utilization in food as alimentary complements are discussed.