Inactivation of Microorganisms in Carbon Dioxide at Elevated Pressure and Ambient Temperature

Abstract

Microorganisms are inactivated remarkably by carbon dioxide at the elevated pressure. The process can be divided into two phases based on the different rate of inactivation: the rate of inactivation is slower at the initial stage and increased sharply at the later stage. The dissolution of CO 2 into the aqueous solution and then diffusion into cells controls the duration and inactivation rate at the early stage. An increase of pressure and temperature enhances the antimicrobial effect of CO 2 under pressure. Inactivation is also affected by agitation and release of pressure. Ethanol is an effective and novel aid to intensify inactivation of microorganisms in CO 2 . E. coli cells after CO 2 treatment are subjected to injury on membranes so as to lose salt tolerance and induce a leakage of intracellular materials. The changes of cell structure and inactivation of several enzymes are observed after treatment. But the most important inactivation mechanism may be the lowering of pH due to the penetration of CO 2 , which leads to the inhibition of certain metabolic and regulating processes.

Inactivation of Lactobacillus fructivorans in physiological saline and unpasteurised sake using CO2 microbubbles at ambient temperature and low pressure

“…The same phenomena were, also, reported in SC‐CO 2 inactivation (Tanimoto et al. , 2007; Wu et al. , 2007), but it was still not clear why SC‐CO 2 efficiency was enhanced by the addition of ethanol.…”

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). Although numerous reports have demonstrated that carbonation at moderate temperature (20 − 40℃) can inactivate microorganisms in their vegetative form, this is not sufficient for substantial reductions in viable spore counts (Garcia-Gonzalez et al, 2007).…”

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends

“…It is noteworthy that at room temperature, S. cerevisiae was killed by 2 log reduction by CO 2 treatment under 5 MPa (Debs-Louka et al, 1999). A significant reduction ratio of 8 log was attained at 6 MPa, 40°C (Kumugai et al, 1997), 7.8 MPa at 35°C (Wu et al, 2007), 13 MPa at 50°C (Ferrentino et al, 2010). Ferrentino et al (2010) published a paper in which they described the inactivation effect at different temperatures (35-50°C) and pressures (7.5-13 MPa), and the results show that the effectiveness of inhibition is enhanced under higher temperature and pressure (Table 3).…”

“…Schmidt et al (2005) and Cinquemani et al (2007) have found that E. coli was completely inhibited with 5-7 MPa CO 2 in only 20 min. Moreover, an increase of pressure, temperature, or treatment time of CO 2 under pressure enhanced the antimicrobial effect against E. coli (Kamihira et al, 1987;Dillow et al, 1999;Wu et al, 2007;Kobayashi et al, 2007Kobayashi et al, , 2009bGarcia-Gonzalez et al, 2010). Thus the use of pressurized CO 2 has been widely investigated (Wu et al, 2007;Kobayashi et al, 2007Kobayashi et al, , 2009aJung et al, 2009;Garcia-Gonzalez et al, 2010;Klangpetch et al, 2011;Cheng et al, 2011).…”

“…Moreover, at high temperature, proteins more easily denatured and the components of external membranes are disintegrated and broken down, so that CO 2 molecules more easily penetrate into the lipid phase and cytoplasm. Most of the recent studies found that increasing temperature led to more effective microorganism inactivation (Kamihira et al, 1987;Dillow et al, 1999;Zhang et al, 2006;Wu et al, 2007;Kobayashi et al, 2009b;Garcia-Gonzalez et al, 2010;Ferrentino et al, 2010;Vo et al, 2013bVo et al, , 2014. However, because rising temperature also decreases the CO 2 solubility in water, a temperature may be reached where no further improvement is gained.…”