Enhancement of sonocatalytic cell lysis of Escherichia coli in the presence of TiO2

An ultrasonic system with TiO2 particles was utilized for disinfection of Escherichia coli (E coli) under condition of darkness. The mechanism of disinfection was studied by investigating the cell lysis and degradation of DNA leaked through the cell membrane. The degradation of DNA was enhanced remarkably in the presence of TiO2 particles. The effects of Al2O3 particles on the degradation of DNA were also examined, and these particles were found to be less effective than TiO2 particles at enhancing degradation. Compared with TiO2 addition case, the ultrasonic irradiation with no particles afforded 5% degradation, while the addition of Al2O3 induced approximately 54% degradation under the conditions used. The role of hydroxyl radicals in this process was also investigated by examining the effects of a hydroxyl radical scavenger, glutathione. A significant suppression of DNA leakage through the cell membrane was observed in the solutions containing glutathione, and the suppressive effects were dose-dependent. These results indicate that hydroxyl radicals may play a primary role in the degradation of DNA as well as cell lysis. (c) 2006 Elsevier B.V. All rights reserved.