The Effects of Fine Bubble Treatments on the Sterilization of <i>Escherichia coli</i> O157 : H7

Abstract

To evaluate the bactericidal property of Fine Bubbles (hereafter, FB), we added a bacterial solution to a solution with or without FB prepared from a nonsterilizing surfactant solution using a mechanical aerating homogenizer. Then, we examined the change in the number of viable bacteria. Our results revealed no changes in the number of viable bacteria owing to the presence or absence of FB, and therefore, the bactericidal effect of FB under these experimental conditions could not be confirmed. Next, an FB solution prepared from a sterilized cationic surfactant solution was added to a bacterial solution. The results demonstrated a decrease in the number of viable bacteria with the addition of the surfactant; however, there was no change in the number of viable bacteria irrespective of whether FB was used. Specifically, no improvement in the bactericidal property of the cationic surfactant owing to the use of FB could be observed. Furthermore, using an FB generation apparatus consisting of a pressurized tank and a circulation tank, and inoculated filter paper and cut lettuce as carriers, we examined the bactericidal effects of air FB and ozone FB treatment on decontamination of E. coli O157: H7. Consequently, although the bactericidal effect of FB in the circulation tank was confirmed, the effect differed depending on the carrier; the bactericidal effect was revealed to be enhanced by increasing dissolved ozone concentration in the pressurized tank due to pressurization, not by FB.