Response surface modeling for the inactivation of Bacillus subtilissubsp. nigerspores by chlorine dioxide gas in an enclosed space

ABSTRACTBacillus subtilissubsp. nigerspores are a commonly used biological indicator to evaluate the disinfection of an enclosed space. In the present study, chlorine dioxide (ClO2) gas was applied to inactivate B. subtilissubsp. nigerspores in an enclosed space. The effects of the ClO2gas concentration (1-3 mg/l), relative humidity (RH, 30-70%) and exposure time (30-90 min) were investigated using a response surface methodology (RSM). A three-factor Box-Behnken experimental design was used. The obtained data were adequately fitted to a second-order polynomial model with an R2adjof 0.992. The ClO2gas concentration, RH and exposure time all significantly (P<0.05) and positively correlated with the inactivation of B. subtilissubsp. nigerspores. The interaction between the ClO2gas concentration and RH as well as that between the exposure time and RH indicated significant and synergistic effects (P<0.05). The predictive model was validated by additional eight experiments and proven to be with good accuracy. Overall, this model established by the RSM could show the trend of the inactivation of spores, indicate the interactions between important factors, and provide a reference to determine effective conditions for the disinfection in different enclosed spaces by ClO2gas.Implications: The inactivation of indoor biological contaminants plays an important role in preventing the transmission of pathogens and ensuring human safety. The predictive model using response surface methodology indicates the influence and interaction of the main factors on the inactivation of Bacillus subtilissubsp. nigerspores by ClO2gas, and can predict a ClO2gas treatment condition to achieve an effective sterilization of enclosed spaces. The results in this paper will provide a reference for the application of ClO2gas treatments for indoor disinfection.