28 research outputs found
Plasma sterilization of Geobacillus Stearothermophilus by O
The aim of this work is to identify the main process responsible for sterilization of Geobacillus Stearothermophilus spores in O2:N2 RF inductively coupled plasma. In order to meet this objective the sterilization efficiencies of discharges in mixtures differing in the initial O2/N2 ratios are compared with plasma properties and with scanning electron microscopy images of treated spores. According to the obtained results it can be concluded that under our experimental conditions the time needed to reach complete sterilization is more related to O atom density than UV radiation intensity, i.e. complete sterilization is not related only to DNA damage as in UV sterilization but more likely to the etching of the spore
Influence of spore size distribution, gas mixture, and process time on the removal rate of B. subtilis spores in low-pressure plasmas
The size reduction of B. subtilis spores due to removal of biological material in low-pressure
plasmas was analyzed in a double inductively coupled plasma system. Argon, nitrogen, and
oxygen at 5 Pa were used as feed gases to investigate the impact of different reactive species
and high energy radiation on the process. The spore size was determined using scanning
electron microscopy images and the length of thousands of spores were evaluated using
an automated algorithm. By applying a statistical test the precision of the mean spore size
determination was increased and the applicability of a normal distribution to describe the
spore size distribution was demonstrated. The removal rate was found to vary depending on
the process gas as well as on the process time and was found to be largest with a mixture of
nitrogen and oxygen and lowest in pure argon. With increasing treatment time the removal
rate decreases significantly and tends to stop in all gases and inhibits the complete removal
of spores and potentially hazardous biological material. Possible explanations for this effect
are the aggregation of non-volatile compounds or the formation of cross-linked layers which
significantly reduce the etching efficiency