Kinetic Modeling of Escherichia coli Inactivation by Ozone Mist

ABSTRACT

Ozone is a strong oxidant, with application in the food industry, disinfection of hospital areas and wastewater treatment. Although microbial destruction with ozone gas and in an aqueous solution has been widely studied, the ability of ozonated mist to inactivate microorganisms remains unknown. Thus, this study aimed to evaluate the kinetic inactivation of Escherichia coli on surfaces by ozone mist, where concentrations up to 51 ppm of ozone were employed. Two scenarios were investigated: surfaces positioned tangentially and 46.5 cm above the mist output, also testing kinetic models of its inactivation (first order and Weibull distribution). Escherichia coli ATCC 25,922, used as reference strain, was inoculated on plate count agar ranging from 10² to 10⁶ CFU/plate by exposing to ozone mist up to 5 minutes. The target bacterium was reduced by 99.99% (4 log cycles) with tangential exposure to the mist output, being considered a satisfactory sanitizer, based on the minimum 4 log required by the sanitary standard. Reduction of 1 log cycle was observed 46.5 cm above the mist output. The Weibull distribution model best represented the inactivation of E. coli over time; predicting that it would take 33 seconds for inactivation of 4 log units of the initial concentration of 10⁶ CFU/plate in surfaces positioned tangentially to the ozone mist output and 7.8 minutes to not detect growth for initial concentration 10² CFU/plate for surface positioned 46.5 cm above the mist output. Thus, the present study demonstrated the effectiveness of ozone mist in inactivating E. coli and could satisfactorily model the kinetics of microbial destruction, allowing for a more assertive and efficient use of this sanitizer.

GRAPHICAL ABSTRACT

KEYWORDS:

• Escherichia coli
• inactivation
• kinetics
• ozone
• ozone mist
• ozonization

Acknowledgments

The authors would like to thank Unisinos University for the infrastructure, FAPERGS for the financial support for this work (Project Number 21/2551-0001918-2), and Instor Projects and Robotics for the ozone mist generator.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul [21/2551-0001918-2].