Inactivation of Escherichia coli and bacteriophage T4 by high levels of dissolved CO2

Abstract

Little information is available regarding the effectiveness of water disinfection by CO(2) at low pressure. The aim of this study was to evaluate the use of high levels of dissolved CO(2) at 0.3-0.6 MPa for the inactivation of microorganisms. Bacteriophage T4 was chosen as the model virus and Escherichia coli was selected as the representative bacterium. The results of the study showed a highly effective log inactivation of E. coli and bacteriophage T4 at low and medium initial concentrations by high levels of dissolved CO(2) at 0.3 MPa with a treatment time of 20 min. When the pressure was increased to 0.6 MPa, inactivation of both microorganisms at high initial concentrations was improved to different extents. Neither pressurized air nor O(2) effectively inactivated both E. coli and bacteriophage T4. The pH was not a key factor affecting the inactivation process by this method. The results of scanning electron microscopy of E. coli and transmission electron microscopy of bacteriophage T4 suggested that "CO(2) uptake at high pressure and bursting of cells by depressurization" were the main reasons for lethal effect on microorganisms. This technology has potential for application in the disinfection of water, wastewater, and liquid food in the future.

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

“…Some authors concluded that decompression rate is an important factor in inactivation due to the expansion of CO 2 into the cells (Fraser, 1951;Lin et al, 1992aLin et al, , 1992bKumugai et al, 1997;Cheng et al, 2011), while others found that it had no significant effect on bacterial inhibition and that mechanical cell bursting did not take place (Li et al, 2013;Debs-Louka et al, 1999;Nakamura et al, 1994;Vo et al, 2013a). Enomoto et al (1997b) found that explosive depressurization with pressures over 4 MPa had a strong effect on inhibition, but not at less than 4 MPa.…”

“…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).…”

“…The antimicrobial effects of the dissolved CO 2 is enhanced by pressurized microbubbles (Ishikawa et al, 1997;Yoshimura et al, 2002;Shimoda et al, 2002;Kobayashi et al, 2007Kobayashi et al, , 2009bKobayashi et al, , 2010Kobayashi et al, , 2012a. Cheng et al (2011) proposed an explosive mechanism such that microbubbles, under sudden discharge, sharply collapsed the working pressure to burst the cell membranes. Takahashi et al (2007) found an interesting explanation, proposing that under acidic conditions the collapse of tiny microbubbles will generate hydroxyl radicals (OH), a strong oxidant.…”

“…Far too little attention has been paid to water disinfection since the first study of Kobayashi et al (2007) have successfully carried out an attempt to transfer knowledge of HPCD from food disinfection to water disinfection. In recent years, there has been an increasing interest in applying HPCD to water treatment (Kobayashi et al, 2007(Kobayashi et al, , 2009a(Kobayashi et al, , 2009b(Kobayashi et al, , 2010Cheng et al, 2011) with the belief that pressurized CO 2 has all the advantages of conventional disinfection methods and overcomes their adverse effects to health. Questions have been raised as to why the major attention on HPCD has been paid to liquid media and water, as shown in Fig.…”

Disinfection Using Pressurized Carbon Dioxide Microbubbles to Inactivate Escherichia coli, Bacteriophage MS2 and T4

“…Supercritical pressure up to 10 MPa and high temperature (55°C) were reported to effectively inactivate E. coli and coliforms -498 - (Kobayashi et al, 2009). However, Cheng et al (2011) concluded that pH was not related to the inactivation mechanism of dissolved CO 2 , which differed from the results of previous studies (Ballestra et al, 1996;Dillow et al, 1999;Hong and Pyun, 1999;Garcia-Gonzalez et al, 2007). Therefore, this study was conducted to investigate the inactivation of pathogenic bacteria (E. coli) and viruses T4 (double-stranded DNA) and MS2 (single-stranded RNA) by CO 2 .…”