Pulsed Electric Field Effects on Cell Viability of the Human Fungal Pathogen Candida albicans

This work evaluates the lethal effects of the main electroporation parameters (field strength, [2.92 - 9.15 kV/cm], pulse duration [0.01 - 0.6 ms], and number of pulses [1 - 10]) on the human pathogen Candida albicans. The latter is chosen as a biological model for microorganisms. Electroporation is applied to a suspension of Candida albicans via a square pulse generator. Plate count method is used to determine the viability of yeast cells. Results show a threshold field strength value, above which, cell viability sharply decreases by increasing field intensity down to zero viability at very high field intensities. This threshold value decreases from 5 to 3 kV/cm by increasing the pulse duration from 10 to 600 mu s. The electric field intensity needed to kill 50% of cells (E50) is shown to decrease at long pulse durations (up to 600 mu s). This can be attributed to the observed increase in delivered charge to 0.58 C and energy to 197 kJ with increase in pulse duration. The present data is essential for the optimization of pulsed electric field protocols for food preservation. It provides a quantitative insight on the origin of the fungicidal effects of pulsed electric fields.