Bacterial inactivation by using near- and supercritical carbon dioxide

Abstract

The three most common methods of sterilization in use today are ethylene oxide exposure, ␥-irradiation, and steam sterilization. Each of these methods has serious limitations for the sterilization of some materials used in medicine, especially thermally and hydrolytically sensitive polymers by themselves and in combination with proteins. In this work, we demonstrate a potential new method of sterilization by using supercritical f luid carbon dioxide. Using this method we achieve complete inactivation of a wide variety of bacterial organisms at moderate temperatures and in the absence of organic solvents or irradiation. Sterilization is a function of both the proximity to the f luid's critical point and the chemical nature of the f luid itself. When biodegradable polymers poly(lactic-co-glycolic) acid and polylactic acid were included in the sterilization process, there was no effect on the inactivation efficiency, yet no physical or chemical damage to these thermally and hydrolytically labile materials was observed.

Effects of Carbonation with Heating on Germination of Bacillus subtilis Spores

“…Dissolved CO 2 is thought to penetrate the cells, and the generated H 2 CO 3 dissociates into HCO 3 − and H + , leading to acidification of the cytoplasm (Dixon and Kell, 1989;Dillow et al, 1999;Spilimbergo et al, 2002). Acidification of cytoplasm has been shown to induce injury and affect the viability of vegetative microbial cells (Kim et al, 2008;Wu et al, 2007).…”

Supercritical carbon dioxide and hydrogen peroxide cause mild changes in spore structures associated with high killing rate of Bacillus anthracis

“…autoclaving, gamma-irradiation, and ethylene oxide) is sorely needed, due to the limitations of these methods and the development of novel polymeric biomaterials which are usually sensitive to these methods (Matthews et al, 2001, Premnath et al, 1996. Steam sterilization damages or destroys heat-sensitive and hydrolytically labile materials (Dempsey and Thirucote, 1989); γ-irradiation may cause changes in shear and tensile strength, elastic modulus, and transparency of polymers (Dillow et al, 1999); and ethylene oxide has significant effect on molecular weight of some biodegradable polymers (Verheyen et al, 1992). Since CO 2 has a relatively low "critical temperature", it is of particular interest as a low temperature sterilization medium.…”

Mammalian cell survival and processing in supercritical CO 2

“…A number of mechanisms have been proposed to explain high-pressure CO 2 sterilization, including cell membrane rupture caused by the increase in internal pressure combined with rapid pressure release (17,18) and the extraction of lipids from the cell membrane (19). Equally, scCO 2 diffusion into the cell and the resultant changes in the cellular environment, such as a decrease in pH, could be lethal (17).…”

“…Equally, scCO 2 diffusion into the cell and the resultant changes in the cellular environment, such as a decrease in pH, could be lethal (17). As a result of this sterilizing power, subcritical CO 2 and scCO 2 has been used to inactivate bacterial cells and spores when injected into poly(lactic acid) for medical sterilization (17) and for sterilization of food stuffs (20). Even short exposure times (150 sec) to CO 2 at just above its critical point (38°C, 74 bar) are sufficient to inactivate both Gram-negative and Gram-positive bacteria (21).…”