Abstract:
The bactericidal mechanisms of low-voltage alternating current
(0-300 mA cm-2) on the bacteria B. cereus were investigated.
The B. cereus cells in logarithmic phase suspended in phosphate buffer
solution (0.2 M) were exposed to alternating current of 50 Hz, 120 V under aerobic
conditions. The related parameters for bactericidal actions by low-voltage alternating
current were measured. At the temperature 29±3°C (non-lethal temperature),
the surviving fractions of cells exposed to Alternating Current (AC) were decreased
with an increase in current density for a definite exposure time. At a certain
current density, the surviving fractions were decreased proportionally with
exposure time. The lethal effect to cells was attributed to the toxicity of
hydrogen peroxide and direct effect of alternating current. These surviving
fractions were closely related to the amount of H2O2 formed
in the cell suspensions. At a definite current density, the amount of H2O2
in the suspension increased with increasing AC-exposure time. At a definite
exposure time, the amount of H2O2 increased with increasing
current density. The H2O2 was produced on the surface
of carbon electrodes by AC-electrolytic reduction of dissolved oxygen. The suitable
condition for efficient bactericidal by low-voltage AC at non-lethal temperature
was AC-exposure at 300 mA cm-2 for 1 h or 200 mA cm-2
for 3 h. This study shows that the low-voltage alternating current method is
a promising technology for the nonthermal pasteurization of foods and is an
appropriate complement or replacement of traditional thermal. Furthermore, the
mechanism of bactericidal activity by AC may offer a useful method for eradicating
bacteria from catheter surfaces.
K. Thamaphat, C. Oopathump and B. Panacharoensawad, 2010. Non-Thermal Lethal Effects of Low-Voltage Alternating Current on Bacillus cereus. Journal of Applied Sciences, 10: 3222-3228.
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