Inactivation of E. coli bacteria by atmospheric dielectric barrier discharge

Dielectric Barrier Discharge (DBD) plasma generated in open air under atmospheric pressure using a homemade pseudo-pulsed high voltage power supply has been used to inactivate Escherichia coli (E. coli). Effects of DBD electrodes gap, applied high voltage and plasma time treatment variations on microorganism's inactivation efficiency have been investigated using optical density measurements and microscopy observations. The decrease in the distance between the DBD reactor electrodes as well as the increase of the applied voltage and/or plasma time treatment induce a significant decrease of the optical density of the treated E. coli cultures. A reduction of about 99% of their optical density has been reached with DBD plasma created using peak-to-peak voltage of 10 kV, a discharge gap of 3 mm and a treatment time of 16 min. This pronounced decrease in the optical density shows an important inactivation of the E. coli microorganisms. This inactivation induced by the DBD plasma discharge has been confirmed by the microscopy observation. A significant decrease of the bacterial cadaver's concentration on the E. coli contaminated glass plate has been observed when the plasma time treatment and/or the applied voltage increased, suggesting by the way that the reactive species created in the air by the plasma DBD have a dominant effect on the sterilisation process.