Post-incubation pH Impacts the Lipid Extraction Assisted by Pulsed Electric Fields from Wet Biomass of Auxenochlorella protothecoides

Abstract

Pulsed electric field (PEF) treatment is a promising technology for efficient lipid extraction from microalgae. This study focusses on under-investigated processing parameters, such as media pH, pulse application, and incubation protocols. The lipid yield and electroporation level of PEF-treated Auxenochlorella protothecoides were determined at a medium pH of 3.0 and 5.0 under variation of the pre- or post-PEF incubation time and for split-dose treatments. Low energetic PEF treatments with 40 kV/cm and 1 μs pulses at 9.6 and 19.2 kJ/L were performed either in batch mode or in continuous flow. Post-PEF incubation significantly increased the shared electroporated cells (>60%) in medium pH 3.0, while no change was observed at pH 5.0. Split-dose PEF treatments at pH 5.0 caused significantly higher electroporation levels and lipid extraction yields than equivalent single-dose treatments. Results have shown that medium pH is critical in the final electroporation and lipid extraction yields of A. protothecoides and therefore should be considered in further studies.