Nitrogen fixation is crucial for plants as it is utilized for the biosynthesis of almost all biomolecules. Most of our atmosphere consists of nitrogen, but plants cannot straightforwardly assimilate this from the air, and natural nitrogen fixation is inadequate to meet the extreme necessities of global nutrition. In this study, nitrogen fixation in water was achieved by an AC-driven non-thermal atmospheric pressure nitrogen plasma jet. In addition, Mg, Al, or Zn was immersed in the water, which neutralized the plasma-treated water and increased the rate of nitrogen reduction to ammonia due to the additional hydrogen generated by the reaction between the plasma-generated acid and metal. The effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated. The germination rate was found to be higher with plasma-treated water and more efficient in the presence of metal ions. Stem lengths and germination rates were significantly increased with respect to those produced by DI water irrigation. The plants responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll and protein contents. Based on this report, non-thermal plasma reactors could be used to substantially enhance seed germination and seedling growth.

In this study, we generated water and phosphate buffer treated with microwave plasma-generated gas in which the major component was nitric oxide (PGNO), and investigated the efficiency of the treated water and buffer in fertilization and sanitation. Real time NO level monitored by an electrode sensor was linearly increased over PGNO injection time, and removal of O₂ from liquid before PGNO injection accelerated NO assimilation into liquids. Residual NO was still present 16 h after PGNO injection was stopped. H₂O₂, NO₂⁻, and NO₃⁻ were also detected in PGNO-treated liquids. Spinach plants applied with 10 and 30 times diluted PGNO-treated water and 0.5 mM phosphate buffer showed slightly higher height and dry weight than control after 5 weeks. Plants grown with 10 and 30 times diluted PGNO-treated water exhibited the increased tolerance to water deficiency. Significant anti-microbial activity within 1 h was observed in un-diluted and in half-diluted PGNO-treated water and 0.5 mM phosphate buffer. Our results suggest that water or phosphate buffer containing NO, H₂O₂, NO₂⁻, and NO₃⁻ can be produced by PGNO treatment, and that PGNO-treated water or buffer can be used as a potential fertilizer enhancing plant vitality with sanitation effect.

In addition to being key pathogens in plants, animals, and humans, fungi are also valuable resources in agriculture, food, medicine, industry, and the environment. The elimination of pathogenic fungi and the functional enhancement of beneficial fungi have been the major topics investigated by researchers. Non-thermal plasma (NTP) is a potential tool to inactivate pathogenic and food-spoiling fungi and functionally enhance beneficial fungi. In this review, we summarize and discuss research performed over the last decade on the use of NTP to treat both harmful and beneficial yeast- and filamentous-type fungi. NTP can efficiently inactivate fungal spores and eliminate fungal contaminants from seeds, fresh agricultural produce, food, and human skin. Studies have also demonstrated that NTP can improve the production of valuable enzymes and metabolites in fungi. Further studies are still needed to establish NTP as a method that can be used as an alternative to the conventional methods of fungal inactivation and activation.

Antifungal activities of MOFs (metal organic frameworks) have been demonstrated in studies, and improvement in efficiency of fungal inactivation is a critical issue in the application of MOFs. In this study, we employed 4,4′-azopyridine (AZPY) in the construction of MOF to improve its antifungal activity. Three-dimensional (3D) copper metal organic framework containing glutarate (Glu) and AZPY (Cu(AZPY)-MOF) was synthesized by a solvothermal reaction. Glutarates bridge Cu₂ dinuclear units to form two-dimensional (2D) layers, and these layers are connected by AZPY to form a 3D framework. When spores of two fungi, Candida albicans and Aspergillus niger, were treated with Cu(AZPY)-MOF for one day, number of CFU (colony forming unit) was continuously reduced over treated MOF concentrations, and maximum 2.3 and 2.5 log₁₀CFU reductions (approximately 99% reduction) were observed in C. albicans and A. niger, respectively. Small amounts of Cu^II ions and AZPY released from Cu(AZPY)-MOF were not critical for fungal inactivation. Our results indicate that the level of antifungal activity of Cu(AZPY)-MOF is greater than that of Cu-MOF without AZPY constructed in our previous study, and intercalation of AZPY is able to improve the antifungal activity of Cu(AZPY)-MOF.

Although non-thermal atmospheric pressure plasma is an efficient tool for preventing post-harvest microbial contamination, many studies have focused on the post-treatment of infected or contaminated foods. In this study, we examined the antimicrobial quality of mushrooms pre-treated with a non-thermal atmospheric pressure plasma jet (NTAPPJ) or plasma-treated water (PTW). The CFU (Colony Forming Unit) number of Escherichia coli inoculated on surfaces of mushrooms pre-treated with NTAPPJ or PTW was significantly reduced (about 60–75% for NTAPPJ and about 35–85% for PTW), and the reduction rate was proportional to the treatment time. Bacterial attachment and viability of the attached bacteria were decreased on NTAPPJ-treated mushroom surfaces. This may be caused by the increased hydrophilicity and oxidizing capacity observed on NTAPPJ-treated mushroom surfaces. In PTW-treated mushrooms, bacterial attachment was not significantly changed, but death and lipid peroxidation of the attached bacteria were significantly increased. Analysis of mushroom quality showed that loss of water content was greater in mushrooms treated with NTAPPJ compared to that in those with no treatment (control) and PTW treatment during storage. Our results suggest that pre-treatment with NTAPPJ or PTW can improve the antibacterial quality of mushroom surfaces by decreasing bacterial attachment (for NTAPPJ) and increasing bacterial lipid peroxidation (for both NTAPPJ and PTW).