Cristina Muja

Surface dielectric barrier discharges (SDBDs) operating in atmospheric air are efficient sources of reactive oxygen and nitrogen species (RONS), making them promising candidates for food decontamination applications. However, their chemical output strongly depends on operating conditions and environmental humidity that can affect treatment efficacy and reproducibility. In this work, we characterize the transition between ozone-dominant (O3 mode) and nitrogen-oxidesdominant (NOX mode) operating regimes by combining ICCD imaging, optical emission spectroscopy, and time-resolved absorption measurements of O3 and NO2 . We demonstrate that an increase of the applied voltage and the dielectric temperature accelerates the shift from net ozone production to rapid O₃ destruction driven by NOx catalytic cycles, while water vapor further suppresses ozone formation through enhanced OH-and H-driven reactions. Spatiotemporal ICCD measurements reveal that humidity simultaneously modifies streamer morphology and enhances overall plasma intensity. These findings establish quantitative operating windows to control RONS production for applications requiring either oxidative (O3 -rich) or nitrosative (NOx -rich) biocidal environments, providing essential knowledge for optimizing plasma-based food safety technologies.

Hospital and urban wastewaters constitute major reservoirs of multidrug-resistant bacteria (MRB), antibiotic resistance genes (ARGs), and persistent pharmaceutical contaminants, which are only partially removed by conventional treatment plants. As a result, these pollutants are frequently detected in treated effluents destined for environmental discharge or reuse, raising serious public health concerns-especially for agricultural irrigation. This study explores a novel immersed dielectric barrier discharge (DBD) plasma source engineered for point-of-use decontamination of wastewater at emission sites. The plasma device was thoroughly characterized by electrical, optical, and chemical diagnostics to elucidate its operating regimes and capacity to generate reactive oxygen and nitrogen species (RONS) at the plasma-liquid interface. Findings demonstrate that the composition of the carrier gas critically shapes the production and transfer of short-and long-lived oxidants into the liquid phase. These results provide quantitative insights that support the ongoing optimization of plasma-based advanced oxidation systems for decentralized water treatment. They further illustrate how the careful control of plasma and gas composition can enhance the formation and transfer of oxidants, contributing to the broader field of plasma-liquid applications for the mitigation of emerging contaminants.

This study investigates low‐pressure microwave air plasma as a non‐thermal decontamination approach for spices, using black peppercorns as a model matrix. At 20 Pa and 80 W, the discharge exhibits electron densities of 10 ⁹ –10 ¹⁰ cm ⁻³ , effective electron temperatures of 0.7 eV, while keeping the substrate temperature below 60°C. Under these conditions 1.2‐log reduction of native aerobic mesophilic and thermophilic flora is achieved after 60 min. Bacillus subtilis spores on peppercorns show a similar 1.2‐log reduction, versus > 6‐log on flat glass carriers, revealing a strong surface shielding effect. UV radiation drives early spore inactivation, while long‐lived reactive species contribute during prolonged exposures. These antimicrobial effects are achieved without significant compromise of the key quality attributes of black pepper.

Bacterial resistance to antibiotics has become a major public health problem in recent years. The occurrence of antibiotics in the environment, especially in wastewater treatment plants, has contributed to the development of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs). Despite the potential of some conventional processes used in wastewater treatment plants, the removal of ARB and ARGs remains a challenge that requires further research and development of new technologies to avoid the release of emerging contaminants into aquatic environments. Non-thermal atmospheric pressure plasmas (NTAPPs) have gained a significant amount of interest for wastewater treatment due to their oxidizing potential. They have shown their effectiveness in the inactivation of a wide range of bacteria in several fields. In this review, we discuss the application of NTAPPs for the degradation of antibiotic resistance genes in wastewater treatment.

Atmospheric pressure plasma processes have been increasingly studied for the microbiological decontamination of liquids. Plasma discharges produce a series of reactive oxygen and nitrogen species (RONS) that diffuse through cell membranes, triggering complex biochemical processes leading to physical and chemical changes in bacteria. The efficiency of plasma liquid decontamination is influenced by the Gram type of bacteria, the bacterial strain, the cell density, and the physiological state of bacteria. The objective of this study was to examine how bacterial growth phases affect the efficiency of plasma liquid decontamination. An atmospheric plasma multijet was used to treat Escherichia coli K12, in the midexponential and stationary phases of growth. The plasma discharge was characterized by optical emission spectroscopy, and the reactive oxygen and nitrogen species (RONS) formed in the treated liquid were quantified by spectrophotometry. The viability assays showed that the growth phase of bacteria influences the effectiveness of the treatment. Cells in the midexponential phase were more susceptible to plasma treatment than stationary-phase cells. After 30 min of plasma treatment, the plasma produced a complete inactivation 7 log reduction in bacteria in the midexponential phase while only a 3 log reduction was observed in stationary phase. Metabolic activity and membrane integrity measurements confirmed the increased sensitivity of exponential phase bacteria compared to stationary cells. In order to study the mechanisms involved in the bactericidal process and cellular defense against plasma-induced oxidative stress, we focused on intracellular ROS levels and genomic DNA damage. The results show a significant difference in intracellular ROS levels between the two phases of growth. However, DNA degradation extent did not reveal any significant differences. These results suggest that a combination of physiological and metabolic responses determine bacterial survival for both growth phases after exposure to plasma treatment.