Decontamination of Bacterial Spores by a Microwave Plasma Torch

Abstract

Summary form only given. Air plasma in a highly energized state, contains radicals such as atomic oxygen, excited oxygen molecules and ozone that are highly reactive. These reactive oxygen species (ROS) can destroy just about all kinds of organic contaminants more effectively than the thermal method. This non-thermal destruction mechanism primarily involves the chemical reactions of ROS with nucleic acids, lipids, proteins and sugars. These chemical modifications result in protein cleavage, aggregation and loss of catalytic and structural function by distorting secondary and tertiary protein structures. These oxidative proteins are irreversibly modified and cannot be repaired. This occurrence is known as protein degradation. Through these chemical reactions, most contaminants are converted by ROS to carbon dioxide and water. The emission spectroscopy of an arc-seed microwave plasma torch (MPT) was examined and the spectral line of O I (777.194 nm) indicating relatively high atomic oxygen content in the torch was detected. This torch was applied to demonstrate this oxidation process for the decontamination of biological warfare agents. In the decontamination experiments, Bacillus cereus was chosen as a simulant of Bacillus anthracis spores for biological agent and the airflow rate was fixed at 0.393 l/s that leads to the maximum concentration of atomic oxygen produced by the torch as well as a good torch size. The results of experiments using dry samples showed that all spores were killed in less than 8 seconds at 3 cm distance, 12 seconds at 4 cm distance, and 16 seconds at 5 cm distance away from the nozzle of the torch. We now extend the experimental effort to decontaminate wet samples. The results will be presented and discussed