Modeling the growth of Aspergillus brasiliensis affected by a nonthermal plasma.

AIM: The main objective of the study was to develop and validate a model for the growth of Aspergillus brasiliensis on surfaces, specifically on agar culture medium. An additional aim was to determine conditions for complete growth inhibition of this micromycete using two different nonthermal plasma (NTP) sources. METHODS AND RESULTS: The developed model uses two key parameters, namely the growth rate and growth delay, which depend on the cultivation temperature and the amount of inoculum. These parameters well describe the growth of A. brasiliensis and the effect of NTP on it. For complete fungus inactivation, a single 10-minute exposure to a diffuse coplanar surface barrier discharge was sufficient, while a point-to-ring corona discharge required several repeated 10-minute exposures at 24-h intervals. CONCLUSIONS: The article presents a model for simulating the surface growth of A. brasiliensis and evaluates the effectiveness of two NTP sources in deactivating fungi on agar media.

Comparison of the Effect of Plasma-Activated Water and Artificially Prepared Plasma-Activated Water on Wheat Grain Properties.

Recently, much attention has been paid to the use of low-temperature plasmas and plasma-activated water (PAW) in various areas of biological research. In addition to its use in medicine, especially for low-temperature disinfection and sterilization, a number of works using plasma in various fields of agriculture have already appeared. While direct plasma action involves the effects of many highly reactive species with short lifetimes, the use of PAW involves the action of only long-lived particles. A number of articles have shown that the main stable components of PAW are H2O2, O3, HNO2, and HNO3. If so, then it would be faster and much more practical to artificially prepare PAW by directly mixing these chemicals in a given ratio. In this article, we review the literature describing the composition and properties of PAW prepared by various methods. We also draw attention to an otherwise rather neglected fact, that there are no significant differences between the action of PAW and artificially prepared PAW. The effect of PAW on the properties of wheat grains (Triticum aestivum L.) was determined. PAW exposure increased germination, shoot length, and fresh and dry shoot weight. The root length and R/S length, i.e., the ratio between the underground (R) and aboveground (S) length of the wheat seedlings, slightly decreased, while the other parameters changed only irregularly or not at all. Grains artificially inoculated with Escherichia coli were significantly decontaminated after only one hour of exposure to PAW, while Saccharomyces cerevisiae decontamination required soaking for 24 h. The differences between the PAW prepared by plasma treatment and the PAW prepared by artificially mixing the active ingredients, i.e., nitric acid and hydrogen peroxide, proved to be inconsistent and statistically insignificant. Therefore, it may be sufficient for further research to focus only on the effects of artificial PAW.

A Review of Microbial Decontamination of Cereals by Non-Thermal Plasma.

Cereals, an important food for humans and animals, may carry microbial contamination undesirable to the consumer or to the next generation of plants. Currently, non-thermal plasma (NTP) is often considered a new and safe microbicidal agent without or with very low adverse side effects. NTP is a partially or fully ionized gas at room temperature, typically generated by various electric discharges and rich in reactive particles. This review summarizes the effects of NTP on various types of cereals and products. NTP has undisputed beneficial effects with high potential for future practical use in decontamination and disinfection.

Effects of Non-Thermal Plasma Treatment on Seed Germination and Early Growth of Leguminous Plants-A Review.

The legumes (Fabaceae family) are the second most important agricultural crop, both in terms of harvested area and total production. They are an important source of vegetable proteins and oils for human consumption. Non-thermal plasma (NTP) treatment is a new and effective method in surface microbial inactivation and seed stimulation useable in the agricultural and food industries. This review summarizes current information about characteristics of legume seeds and adult plants after NTP treatment in relation to the seed germination and seedling initial growth, surface microbial decontamination, seed wettability and metabolic activity in different plant growth stages. The information about 19 plant species in relation to the NTP treatment is summarized. Some important plant species as soybean (Glycine max), bean (Phaseolus vulgaris), mung bean (Vigna radiata), black gram (V. mungo), pea (Pisum sativum), lentil (Lens culinaris), peanut (Arachis hypogaea), alfalfa (Medicago sativa), and chickpea (Cicer aruetinum) are discussed. Likevise, some less common plant species i.g. blue lupine (Lupinus angustifolius), Egyptian clover (Trifolium alexandrinum), fenugreek (Trigonella foenum-graecum), and mimosa (Mimosa pudica, M. caesalpiniafolia) are mentioned too. Possible promising trends in the use of plasma as a seed pre-packaging technique, a reduction in phytotoxic diseases transmitted by seeds and the effect on reducing dormancy of hard seeds are also pointed out.

Influence of non-thermal plasma on structural and electrical properties of globular and nanostructured conductive polymer polypyrrole in water suspension.

Non-thermal plasma has proved its benefits in medicine, plasma assisted polymerization, food industry and many other fields. Even though, the ability of non-thermal plasma to modify surface properties of various materials is generally known, only limited attention has been given to exploitations of this treatment on conductive polymers. Here, we show study of non-thermal plasma treatment on properties of globular and nanostructured polypyrrole in the distilled water. We observe that plasma presence over the suspension level doesn't change morphology of the polymer (shape), but significantly influences its elemental composition and physical properties. After 60 min of treatment, the relative concentration of chloride counter ions decreased approximately 3 and 4 times for nanostructured and globular form, respectively and concentration of oxygen increased approximately 3 times for both forms. Simultaneously, conductivity decrease (14 times for globular and 2 times for nanostructured one) and changes in zeta potential characteristics of both samples were observed. The modification evolution was dominated by multi-exponential function with time constants having values approximately 1 and 10 min for both samples. It is expected that these time constants are related to two modification processes connected to direct presence of the spark and to long-lived species generated by the plasma.