Enzyme activity modeling intracellular processe

The mechanisms of CO2 toxicity at near-atmospheric pressures are amplified at the near-critical and supercritical pressures used to achieve sterilization. For example, Spilimbergo et al. (9) examined the mechanism of inactivation of Pseudomonas aeruginosa and B. subtilis at 38-54°C and 5.8-20 MPa in a batch process. Total inactivation of the bacteria was observed when exposed to SCF CO2 at 38°C and 7.4 MPa for 150 s. The mechanism of inactivation is suggested to involve (a) the diffusion of SCF CO2 into the cells leading to a drop in pH and a subsequent loss of activity of key enzymes and (b) the extraction by SCF CO2 of intracellular substances, including phospholipids. Further analysis determined a high solubility of CO2 in model cell membrane phospholipids, suggesting that the enhanced permeability of the membrane in the presence of CO2 contributed to the inactivation of the cells. 

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