Application of mathematical models for bacterial inactivation curves using Hypericin based photosensitization

Aims The aim of this study was to evaluate which of the three mathematical models (Weibull, Geeraerd and Logistic) makes the best approximation for Hypericin-based photosensitization bacterial inactivation. Methods and Results The inactivation of common food-borne pathogens Listeria monocytogenes and Bacillus cereus has been analysed. Three models, Weibull, Logistic and Geeraerd, have been used for different treatment conditions (10−7 mol l−1 and 10−8 mol l−1 Hypericin concentrations and 2 and 60 min incubation time). The Logistic method showed better correspondence (estimated R2 ≥ 0·98, RMSE ≤ 0·41), than the Weibull (estimated R2 ≥ 0·91, RMSE ≤ 0·90) and the Geeraerd model (R2 ≥ 0·83, RMSE ≤ 1·27). After evaluation of best fitting model for the dependence of bacterial population reduction on irradiation time, the parameters describing treatment efficiency have been calculated. Conclusions Our results indicate that the Logistic model described in the best way the inactivation of B. cereus and L. monocytogenes by Hypericin-based photosensitization. Significance and Impact of the Study This study identified a best model for describing bacterial inactivation by hypericin-based photosensitization, which provides a way to evaluate the efficacy of different treatment conditions for this novel decontamination technique.