The influence of pulsed electric fields with different waveforms on the extraction of valuable compounds from microalgae

The influence of pulsed electric fields with different waveforms on extracting valuable compounds from microalgae was investigated. Four different waveforms (rectangle, bipolar rectangle, oscillating superimposed rectangle, and two-step rectangle) with the same amplitude (25 kV/cm) and energy (4 J/pulse) were generated using a pulsed power generator to induce electroporation and component release of three species of microalgae. For Nannochloropsis and Spirulina platensis, the oscillating superimposed rectangular pulse increased the conductivity of microalgal suspensions twice as much as the other waveforms. For Chlorella vulgaris, the protein extraction effect of the oscillating superimposed rectangular pulse was 70 % higher than that of the conventional unipolar rectangular pulse. The pulse waveforms did not show significant differences in the extraction of small molecules, with the carbohydrate extraction index exceeding 0.3 for four waveforms. The results showed that the pulse waveforms were important for extracting large molecules (e.g., proteins). Reasonably designed pulse waveforms for different species of microalgae can significantly improve protein extraction or selectively extract carbohydrates.