Publications

Selected publication  

Kimani B.G., Mehrabifard R., Galmiz O., Machala Z.,: Enhanced Yeast Inactivation by Plasma-Activated Water in Combination with Natural Bioactive Compounds, ICPM11&IWPCT10, Nagaragawa Convention Center, Gifu Japan, May 31 - June 5, p. 1 (2026).
citations: 0

Abstract

Effective fungal control is crucial for preventing spoilage, contamination, and infection in food,
healthcare, and industrial settings [1]. Yeasts present a constant challenge because they can adhere to
surfaces and form biofilms, which makes them more resistant to standard antimicrobial treatments.
Cold atmospheric plasma (CAP) provides non-thermal antimicrobial strategy by generating reactive
oxygen and nitrogen species (RONS) such as H₂O₂, NO₂⁻, NO₃⁻, O₃ and •OH [2]. Plasma-activated
water (PAW) has emerged as a promising indirect plasma method with significant antifungal potential
[2, 3]. Natural bioactive compounds, such as phenolics and essential oils have antifungal properties
just like synthetic antifungals, however, practical use of these compounds often encounters issues
with stability, solubility, and bioavailability [4]. Combining these compounds with PAW can greatly
improve their effectiveness and expand their range of action.
This study investigates the antifungal activity of PAW produced using a 1 kHz transient spark (TS)
discharge combined with natural compounds. PAW was mixed with single phenolic compounds
(cinnamic acid, vanillin, p-coumaric acid, and gallic acid) and single essential oils (carvacrol, thymol,
and eugenol) and characterized against planktonic growth, biofilm formation, and surface adhesion
of Wickerhamomyces anomalus SZMC 8061Mo, Saccharomyces cerevisiae SZMC 1279,
Schizosaccharomyces pombe SZMC 1280, and Debaryomyces hansenii SZMC 8045Mo. PAW was
generated by exposing 10 mL of sterile tap water to TS discharge for 10 minutes which produced
water containing RONS. Yeast strains were grown for 24 hours at 30 °C, diluted to required
concentrations and treated with PAW, single natural compounds, or their combinations. The
antifungal efficacy was measured by counting viable colonies on agar plates of treated samples and
compared with the untreated control, while biofilm structure was analyzed using fluorescence
microscopy.
Combined treatments consistently showed better anti-yeast activity than the individual agents.
Mixing PAW with natural compounds led to significant decreases in growth and major disruption of
biofilm development. Overall, combining cold plasma-derived reactive species with natural bioactive
compounds provides an effective and sustainable method for controlling yeast. This strategy shows
great potential in antifungal surface cleaning and creation of non-antibiotic antimicrobial methods.
This research was funded by the EU NextGenerationEU through the Recovery and Resilience Plan
for Slovakia under the project 09I03-03-V03-00033 EnvAdwice and Slovak Research and
Development Agency APVV-22-0247. Dr. Miklos Takó provided the yeasts from the University of
Szeged Microbiological collection.
References
[1] Do Nascimento, Dos Santos, and Samile, De Araújo, Aerobiology, 1, 3-18 (2023).
[2] Polčic, and Machala, International Journal of Molecular Sciences, 22, 2247 (2021).
[3] Domonkos, Tichá, and Trejbal, Applied Sciences, 11, 4809 (2021).
[4] Cho, Jung, and Rho, Food Science and Biotechnology, 34, 2475-2488 (2025).