Inactivation of Leuconostoc dextranicum with carbon dioxide under pressure

Inactivation of micro-organisms with pressurized carbon dioxide at both supercritical and subcritical temperatures has been studied recently. This method differs conceptually from other processes in that the action of cell inactivation is prompted primarily by the extraction of intracellular substances from cells or cell membranes. Disturbance or damage to the balance of the biological system of the cell can cause death without rupture of the cell wall. Experimental results showed that Leuconostoc dextranicum cells were inactivated at least 10⁸-fold at 35 °C in 15 and 20 min under CO₂ pressures of 1000 and 3000 lbf in⁻² respectively. Subcritical carbon dioxide is less effective, requiring about 40 and 35 min at these pressures to inactivate the same amount of cells. The inactivation rate is controlled essentially by the penetration of CO₂ into the microbial cells, which at a sufficient level extracts lipids or other vital constituents to achieve the lethal effect. Various important parameters of the inactivation process are explored.