Inactivation of Escherichia coli by several types of gas bubbles

Abstract

Abstract The ability of gas bubbles to inactivate Escherichia coli suspended in distilled water at varied temperature and several types of gas, namely carbon dioxide, nitrogen and argon, was investigated. The results of the experiment showed that carbon dioxide gas bubbles gave the better inactivation of Escherichia coli than other gasses and the number of surviving Escherichia coli was reduced by approximately 0.76-log from the treatment of carbon dioxide gas bubbles at 4-10°C and gas flowrate of 2.5 ml/min for 40 min. The pH of solution after treatment with carbon dioxide gas bubbles for 40 min was 3.8. Furthermore, the number of surviving Escherichia coli was reduced by approximately 1.62-log when the solution temperature was increased to 50°C with the same condition of the treatment of carbon dioxide gas bubbles at 4-10°C. It was found that the addition of carbon dioxide gas bubbles together with increasing the solution temperature can significantly reduce the number of Escherichia coli. The most suitable of inactivation kinetics reaction was first order and the rate constant, k, at 4-10°C, 30°C and 50°C was 0.0220, 0.0013 and 0.0475 min -1, respectively. The decimal reduction time D at 4-10°C, 30°C and 50°C was 45.45, 769.23 and 21.05 min, respectively.