Mathematically modelling the inactivation kinetics of Geobacillus stearothermophilus spores: Effects of sterilization environments and temperature profiles

Abstract

In this study, inactivation kinetics of Geobacillus stearothermophilus spores were evaluated in different sterilization environments. The kinetics were analysed and mathematically modelled based on experimental data collected. The inactivation kinetics were measured precisely in moist heat environments using different sterilization temperatures and holding times. All measured inactivation times were shorter than the inactivation time indicated by the Biological Indicator (BI) manufacturer. Increasing sterilization efficiency was found in the following environments: air, saturated steam, wet steam, liquid water, dialysis solutions. Applying first- and second-order reaction kinetics approaches, formulas were derived from measured data that enabled bacterial inactivation to be modelled. A mathematical first-order reaction kinetic modelling approach could be taken to effectively predict inactivation kinetics for G. stearothermophilus spores based on the experimentally measured data collected in wet steam and air environments. A second-order reaction kinetics approach could be taken, however, to model measured data more accurately in liquid water and dialysis-solution environments. The mathematical models presented here can be applied to describe inactivation kinetics for G. stearothermophilus spores in different sterilization test environments or for any given sterilization temperature profile. These findings can be used to improve the quality of sterilization processes.