Kinetics of the Inactivation of <i>Vibrio parahaemolyticus</i> in Weakly Acidic Sodium Chlorite Solution

Abstract

The kinetics of the inactivation of Vibrio parahaemolyticus in sodium chlorite NaClO 2 solution was studied in the weakly acidic pH range of 4.0 to 6.5 and at various temperatures. The logarithmic reduction of the survival ratio depended on the concentration-time product, and all the inactivation curves showed a linear reduction phase. The first-order inactivation rate constant k increased by approximately twice for every 0.44 unit fall in pH. During the inactivation experiments, no formation of chlorine dioxide occurred. These data indicated that undissociated HClO 2 was the active species governing the inactivation of V. parahaemolyticus. It was also shown that the use of weakly acidic NaClO 2 solutions containing high concentrations of ionized ClO 2 -gave slower kinetics of the inactivation, whereas it could achieve the significant reduction of viable cells of more than 4-log. The k value showed an Arrhenius-type temperature dependence in the temperature range of 5 to 40 . The apparent activation energy for the inactivation of V. parahaemolyticus was estimated to be 43.5 kJ/mol. The k value increased by approximately 1.8 times for every 10 rise in temperature.

Efficacy of sodium chlorite in inactivating <i>Vibrio parahaemolyticus</i> attached to polyethylene terephthalate surfaces

“…A 50-mL aliquot of 0.1 M sodium phosphate buffer containing 0.9% NaCl (PBS, pH 4.0 -6.5) was put into a 50-mL glass beaker and then set in a thermostatic bath (25 mmol•min at pH 4.0 and 0.107 L/mmol•min at pH 6.5 (see Table 1) (Takahashi et al, 2017b) . The k values obtained in this study were approximately half of the k unatch values at each pH.…”

“…(2) indicates that the k value increases by approximately 4.5-fold for every 1.0 unit fall in pH. In case of the unattached V. parahaemolyticus cells, the k unatch value was calculated to increase by approximately 4.0-fold for every 1.0 unit fall in pH (Takahashi et al, 2017b) . These findings indicate that the higher inactivation effect was due to the high concentrations of undissociated HClO 2 .…”

“…Inactivation experiments were conducted at 25℃. a The k unatch values were adapted fromTakahashi, et al, 2017b and denote the first-order inactivation rate constant of unattached V. parahaemolyticus.…”