Bactericidal Effect of Nanopulse Generated Plasma on Bacillus subtilis Spores at Different Humidity Levels

ABSTRACT The antimicrobial properties of non‐thermal plasma (NTP) offer promising applications in sterilizing temperature‐sensitive materials. This study investigates how treatment parameters affect the inactivation of Bacillus subtilis spores using a surface dielectric barrier discharge powered by a nanopulse supply. This setup enables NTP exposure without direct sample contact and under controlled conditions. The effects of sample distance (3−45 mm), exposure time (5–30 min), and relative humidity (RH) (40%–90%) were evaluated. Sporicidal activity was assessed using a previously established protocol, and gas‐phase species in NTP were analyzed by Fourier‐transform infrared spectroscopy (FTIR). All parameters significantly influenced inactivation. Notably, 90% RH led to up to 4‐log greater spore reduction, highlighting the critical role of humidity in enhancing NTP efficacy.