Kinetics of bacterial death by heated dolomite powder slurry

The kinetics of the bactericidal action of dolomite powders heated at 600–1000 °C against Escherichia coli and Staphylococcus aureus were investigated. Dolomite powder heated to at least 700 °C exhibited bactericidal action, and the process of bacterial death in the heated dolomite powder slurries followed first-order reaction kinetics. The value of the death rate constant (k) increased with dolomite powder concentration, and the dilution coefficient (n), which indicates the dependence of k on the reagent concentration, was measured. The n values of the powder heated at 700 °C and at temperatures >900 °C were almost identical to those of MgO and CaO, respectively. This suggests that the first emergence of bactericidal action at 700 °C corresponds to generation of MgO while that at temperatures >900 °C is due to generation of CaO. The slurry temperature significantly affects the bactericidal action. The slope of the Arrhenius plot of k for E. coli and S. aureus grown at 37 °C exhibited a discontinuous point at approximately 22 °C, where a change in the value of activation energy for bacterial death occurred. This temperature corresponds to that of the phase transition of cell membrane lipids.