Inactivation of Vegetative Microorganisms and Bacillus atrophaeus Endospores by Reactive Nitrogen Species (RNS)

Abstract

Plasma is used as a common technology for the treatment and modification of surfaces in a variety of industrial branches. Decontamination of inorganic materials by plasma is possible with deterioration of the materials properties of a few nanometres. The inactivation efficacy of microwave plasma processed air against vegetative bacteria and bacterial endospores was investigated. The gained results provide inactivation rates up to 6 log in total treatment times (15–30 min) comparable to sterilization treatment times of thermo‐sensitive medical devices with ethylene oxide, formaldehyde or H2O2. Additions like O2 or O3 did not promote the antimicrobial efficacy. Moreover, this new method is characterized by advantages like no thermal influence, no toxicity for human and environment and low costs.

Characterising the impact of post‐treatment storage on chemistry and antimicrobial properties of plasma treated water derived from microwave and DBD sources

“…The microwave driven plasma system used in this study generates NO 2 in high concentrations which is visible as a brown gas inside the glass bottles and has been identified as the predominant species using MS in previous studies . The colour dissipates within minutes of storage time in closed containers indicating dissolution of NO 2 into the liquid and/or further reactions.…”

“…Work by Lukes and co‐workers has demonstrated the pH dependent reaction of H 2 O 2 and nitrite to form peroxynitrite, a reaction which could be a cause for the absence of detectable H 2 O 2 in PTW‐MW and undetectable levels of nitrite in PTW‐DBD. However, previous studies detected no O • , O 2 • , OH • or O 3 and indicated a lack of ROS generated by the MW plasma device due to high gas temperatures in the centre of the plasma . For the DBD device which generates high concentrations of H 2 O 2 , a reaction with nitrite during/directly post discharge is possible and could have resulted in the formation of the detected NO 3 − .…”

“…Non‐thermal plasma treatment of deionized water was performed using the microwave driven discharge PLexc ® (plasma excited device) built at Leibniz Institute for Plasma Science and Technology e. V. (Greifswald, Germany) which has been described in detail . Typical operation data used for this work are shown in Table .…”

“…Non-thermal plasma treatment of deionized water was performed using the microwave driven discharge PLexc ® (plasma excited device) built at Leibniz Institute for Plasma Science and Technology e. V. (Greifswald, Germany) which has been described in detail. [14] Typical operation data used for this work are shown in Table 1. The torch like discharge was ignited for 5, 25, or 50 s at 2.45 GHz and generated plasma treated air (PTA), which was introduced into a 250 ml laboratory glass bottle (Duran Group GmbH, Mainz, Germany) filled with 10 ml sterile deionized water and generated plasma treated water (PTW-MW) ( Figure 1).…”

“…[13] The role of a post-treatment storage time under gas-sealed conditions in modulating the chemical composition and biological activity in particular was investigated for plasma-treated water from a ROS-rich DBD discharge and a RNS-dominated MW-dirscharge, respectively, and highlights that plasma treated water from different sources has very distinct characteristics. [14] O 3 (2000-16000 ppm); N 2 O 4 (1000 ppm); NO 2 (1000 ppm); N 2 O 5 (1000 ppm); NO 3 (10-100 ppm) (treatment time 1 min, 2 min) [15] 2 | EXPERIMENTAL SECTION…”