Kinetics of bacterial death by heated dolomite powder slurry

The kinetics of the bactericidal action of dolomite powders heated at 600-1000 degrees C against Escherichia coli and Staphylococcus aureus were investigated. Dolomite powder heated to at least 700 degrees 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 degrees C and at temperatures > 900 degrees C were almost identical to those of MgO and CaO, respectively. This suggests that the first emergence of bactericidal action at 700 degrees C corresponds to generation of MgO while that at temperatures > 900 degrees 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 degrees C exhibited a discontinuous point at approximately 22 degrees 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. (c) 2005 Elsevier Ltd. All rights reserved.