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Mathematical Modeling for Evaluating Inherent Parameters Affecting UVC Decontamination of Indicator Bacteria
Phetcharat Jaiaue1, Jirabhorn Piluk2, Kanokon Sawattrakool3
1Program in Biotechnology, Faculty of Science, Chulalongkorn Universitygrid.7922.e, Bangkok, Thailand.
Applied and Environmental Microbiology
|March 15, 2022
Summary
This study shows the Chick-Watson model accurately predicts bacterial inactivation by UVC light. Gram-positive bacteria exhibit higher UVC resistance than Gram-negative bacteria due to their cell wall composition and DNA.
Area of Science:
- Microbiology and Environmental Science
- Biophysics and Mathematical Modeling
Background:
- Ultraviolet (UV) light, particularly UVC, is a critical nonthermal physical decontamination method used globally for microbial inactivation.
- Traditional methods for determining sufficient UV doses are often unreliable, necessitating accurate kinetic models for effective UV treatment system design.
- Understanding microbial UVC sensitivity is crucial for public health, especially in light of pandemics and the need for effective pathogen control.
Purpose of the Study:
- To investigate bacterial inactivation kinetics using a custom-designed UVC apparatus.
- To evaluate the predictive performance of linear and nonlinear mathematical models, specifically the Chick-Watson, Weibull, and modified Chick-Watson models.
- To determine the influence of UVC irradiation intensity and bacterial characteristics on inactivation rates.
Main Methods:
- An in-house UVC apparatus was utilized to irradiate five indicator bacteria: Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus faecalis, and Bacillus subtilis.
- Bacterial inactivation kinetics were modeled using linear and nonlinear mathematical approaches.
- Statistical analyses were performed to assess the significance of irradiation intensity and bacterial groups on the death rate coefficient (k).
Main Results:
- The Chick-Watson model demonstrated a superior fit to experimental data for all five tested bacteria compared to Weibull and modified Chick-Watson models.
- The specific death rate (k) significantly increased with higher UVC irradiation intensity (I).
- Gram-positive bacteria exhibited higher UVC resistance (higher k values) than Gram-negative bacteria, attributed to their thicker peptidoglycan layer and higher guanine-cytosine (GC) content.
Conclusions:
- The Chick-Watson model provides a reliable method for predicting bacterial inactivation kinetics under UVC treatment.
- Bacterial intrinsic factors, including cell wall structure and DNA GC content, significantly influence UVC susceptibility.
- This research enhances the understanding of UVC-induced bacterial inactivation, aiding in the optimization of UV disinfection systems.
