Cell Membrane Permeabilization Studies of <italic>Chlorella</italic> sp. by Pulsed Electric Fields

Abstract

Microalgae cell membrane permeabilization has been studied, for Chlorella sp., in a continuous 6-L prototype for different field strengths in order to minimize the specific energy supplied and the treatment time. Regarding lower electrical field strength values, the optimal results were achieved at 10 kV/cm, 200 Hz, and 5-µs per pulse, corresponding to an energy delivered of 9 kJ/kg of culture, with 97% of cells affected after 300 ms of treatment time. Regarding energy delivered per kilogram of Biomass, the best result was 2.7 MJ/kg of biomass with 95% of cells affected after 300 ms of treatment time and was achieved at 15 kV/cm, 200 Hz, and 5-µs per pulse. Pulsed electric field effect was quantified by flow cytometry using propidium iodide as a viability stain. The influence of conductivity and cell concentration was also analyzed. The final goal was to evaluate the use of this technology in terms of increasing bioaccessibility of bioactive compounds present in microalgae for food and feed purposes. These results, obtained only for chlorophyll a and b, did not show any beneficial effect of this technology against nontreated biomass.Index Terms-Bioaccessibility, Chlorella, electroporation, microalgae, pulsed electric field (PEF).

Kinetic Modeling and Numerical Simulation as Tools to Scale Microalgae Cell Membrane Permeabilization by Means of Pulsed Electric Fields (PEF) From Lab to Pilot Plants

“…The presented experimental results indicate that a minimum specific energy input of 19.6 kJ kg −1 is necessary to perforate 100% of the cells in electroporation cuvettes. These results are in good agreement with the work of Rego et al (2015), who treated Chlorella cells in a continuous treatment chamber with a parallel plate electrode configuration. According to their results, about 20 kJ kg −1 were necessary for permeabilizing 100% of the treated cells.…”

“…Fourth, it should be mentioned that the model calibration was done at a dry mass content of 1 g l −1 . Nevertheless, it was shown that the PEF treatment of microalgae is independent of the biomass concentration up to concentrations 160 g l −1 for Auxenochlorella protothecoides (Goettel et al, 2013) and 40 g l −1 for Chlorella vulgaris (Rego et al, 2015) (higher concentrations were not tested in the cited papers). Based on these results, the validity of the proposed model at higher biomass concentrations seems likely, although it should be proved in future work.…”

Nutritional Profiling and Preliminary Bioactivity Screening of Five Micro-Algae Strains Cultivated in Northwest Europe

“…Yet, an enzymatic disruption could not increase chlorophyll release in C. vulgaris biomass [ 61 ]. Similarly, a mechanical disruption treatment was unnecessary when chlorophyll bio-accessibility was considered in C. vulgaris biomass, with bio-accessibility values already ranging between 77–84% for untreated biomass [ 62 ]. No literature was found on fatty acid release during C. vulgaris digestion.…”

Recent Trends in Extraction Techniques for High Value Compounds from Algae as Food Additives

“…In addition to increasing yield, PEF allows to eliminate removing the water stage for fresh water algae. The working principle of the PEF was explained as cell membrane electropermeabilization or electroporation by electromechanical compression and electric field-induced tension in many studies (Luengo et al, 2014;Rego et al, 2015;Parniakov et al, 2015;Eing et al, 2013;Zbinden et al, 2013). Electroporation results in an increase in permeability of cell membrane to ions and macromolecules because of local defects or pores in the cell membrane (Parniakov et al, 2015).…”