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Inactivation of Saccharomyces cerevisiae in solution by low-amperage electric treatment

Guillou, S., El Murr, N.
Journal of applied microbiology 2002 v.92 no.5 pp. 860-865
Saccharomyces cerevisiae, electric current, electrical treatment, electrochemistry, electrodes, electrolysis, heat, hydrogen peroxide, ionic strength, ohmic heating, pH, phosphates, platinum, statistical analysis, synergism, temperature, toxicity, yeasts
Aims: The objectives of this study were to investigate the potential application of a low-amperage direct electric current as a non-thermal process for inactivation of Saccharomyces cerevisiae. Methods and Results: Electric current was generated using a direct current power supply connected to a traditional electrochemical cell with two platinum electrodes immersed in conducting solution containing a population of S. cerevisiae. This treatment provoked inactivation of the yeast cells. The microbial destruction illustrated by D-values calculated from survival curves was shown to be proportional to the current amperage (i) (D varies from 1547 min to 140 min when i varies from 0.1 to 1 A, respectively). The efficacy of the treatment was shown to be better at pH < 7. Statistical analysis showed no significant effect (P > 0.05) of ionic strength on yeast lethality induced by electrolysis. Conclusions: The lethal effect of the electric treatment on S. cerevisiae in phosphate buffer was shown to be due to neither ohmic heating nor toxic hydrogen peroxide. A synergistic effect of temperature and electrolysis was observed when the temperature became lethal for the yeast. Significance and Impact of the Study: The method described for yeast lethality induced by electrolysis has potential for soft sterilization, particularly when combined with the synergistic effect of moderate heat.