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To investigate the effect and mechanism of plasma-activated water (PAW) on Aspergillus niger, PAW was prepared using a needle array–plate dielectric barrier discharge plasma system. The concentrations of long-lived reactive oxygen and nitrogen species (RONS), namely, H2O2, NO2−, and NO3−, in the PAW were 48.76 mg/L, 0.046 mg/L, and 172.36 mg/L, respectively. Chemically activated water (CAW) with the same concentration of long-lived RONS was also prepared for comparison. A. niger A32 was treated with PAW and CAW. After treatment, the treated strains were observed and analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to screen probable mutants. The results indicated that the pH, conductivity, and ORP values of PAW were 2.42, 1935 μS/cm, and 517.07 mV, respectively. In contrast, the pH and ORP values of CAW were 6.15 and 301.73 mV, respectively, which differed significantly from those of PAW. In addition, the conductivity of CAW showed no change. SEM and TEM analyses revealed that A. niger A32 treated with CAW exhibited less damage compared with the control. In contrast, A. niger A32 treated with PAW showed significant shrinkage, deformation, and exudate attachment over time. Following PAW treatment, after four passages, a high cellulase-producing stable mutant strain A-WW5 was screened, exhibiting a filter paper enzyme activity of 29.66 U/mL, a cellulose endonuclease activity of 13.79 U/mL, and a β-glucosidase activity of 27.13 U/mL. These values were found to be 33%, 38%, and 2.1% higher than those of the original fungus sample, respectively. In total, 116 SNPs and 61 InDels were present in the genome of the mutant strain A-WW5. The above findings indicate that the impact of PAW on A. niger is not only attributed to long-lasting H2O2, NO2−, and NO3− particles but also to other short-lived active particles; PAW is expected to become a new microbial breeding mutagen. [ABSTRACT FROM AUTHOR]

High-voltage discharge plasma drying (HVDPD) is a non-thermal and efficient drying technique. In this study, we compared the drying characteristics and physicochemical properties of alfalfa dried via HVDPD, hot-air drying (HAD), and natural air-drying (AD) and analyzed the experimental results using infrared spectroscopy, scanning electron microscopy, colorimetry, and other detection techniques. The results showed that HVDPD had a higher drying rate than AD and saved more energy than HAD. Alfalfa dried via HVDPD had the most intact internal structure, the highest rehydration ratio (RR), the best color quality, and the best nutrient retention, resulting in the highest relative quality and feeding value. Therefore, HVDPD is an excellent drying technique for alfalfa, providing a new and effective way to improve the storage, transportation, and drying quality of alfalfa. [ABSTRACT FROM AUTHOR]

Alfalfa seeds were directly treated with corona discharge plasma radiation and compared with the control group, which was covered by a Petri dish, blocking the etching effect of ionic wind and thus simulating the effect of a non-uniform electric field. The results showed that corona discharge plasma radiation changed the chemical structure of the seed coat. The peak value of the Fourier transform infrared spectrum of the seed coat at 2 856 cm‒1 and 1 729 cm‒1 changed after treatment, indicating that the wax, lipids, and cellulose in the seed coat may have been degraded. Measurements of the seed floating rate and apparent contact angle in the treated seeds compared to the measurements in the control group indicated that corona discharge plasma radiation also improved the hydrophilicity of the alfalfa seeds. In the control group, the Petri dish cover effectively reduced the physicochemical etching by ionic wind; thus, it appears that ionic wind has a greater influence on the seed coat than does the non-uniform electric field. Scanning electron micrograph images showed that the etching of the seed coat in the treated seeds was severe; the cellulose of the seed coat was degraded, and the surface was cracked, which improved the water absorption capacity of the seed. The seedling height of the seeds treated with corona discharge plasma radiation increased significantly compared to that of the control group, indicating that the physicochemical etching of the ionic wind had resulted in a macroscopic biological effect. This study provides experimental data support for the analysis of surface modification and chemical structure composition of alfalfa seeds treated with corona discharge plasma radiation and also provides a basis for further study of the biological effect mechanism of the corona discharge field.

This study investigated the impact of high-voltage electric field (HVEF) thawing technology on the thawing rate, water retention characteristics, microstructure, and nutritional composition of thawed beef. Compared with the control group, in which thawing occurred under natural conditions, the experimental group, in which beef was thawed under HVEF (12 kV, 16 kV, 20 kV, 24 kV, 28 kV), showed a significantly shorter thawing time, and the higher the voltage was, the faster the thawing rate. The total loss rate of thawed beef reached its minimum value of (54.2 ± 0.62) % at 28 kV, and the water retention of the experimental group was significantly better than that of the control group (p < 0.05). Therefore, it can be concluded that HVEF thawing enhances the water retention ability of beef. In a color comparison, it was evident that the color of the beef thawed by HVEF was significantly better than that of the control group. The results of scanning electron microscopy (SEM) indicated that thawing beef by HVEF can reduce the damage to the myofibril structure. Low-field nuclear magnetic resonance (LF-NMR) showed that beef thawed by HVEF had a significantly increased bound water content. According to the determination of malondialdehyde content, beef thawed by HVEF had a reduced degree of lipid oxidation; the content at 16 kV was 2.4 mg/kg, and the degree of lipid oxidation was the lowest. Fourier transform infrared (FTIR) spectroscopy analysis revealed that the absorption peak positions of the beef samples did not show significant changes under different conditions. However, the absorption peak intensity in the experimental group was generally higher than that in the control group. Examination of the protein secondary structure via infrared spectroscopy revealed that, compared with the control group, HVEF thawing transformed the proteins from an ordered structure to a disordered structure. The increase in disordered structure reduced the fiber gap of the sample and improved the water retention of the beef. The above experimental results indicate that HVEF thawing can improve the water-holding capacity of the sample and reduce the thawing damage to the quality of the sample. [ABSTRACT FROM AUTHOR]

In this study, the seeds of Medicago truncatula are treated with plasma and plasma‐activated water (PAW), and the RNA sequencing (RNA‐Seq) of the seedlings is performed to analyze the gene expression changes. It is found that plasma treatment has no significant effect on seed survival rate, but PAW has an obvious lethal effect. Both methods result in the differential expression of a large number of genes in seedlings, and the expression of genes with the function of promoting plant growth and metabolism is significantly upregulated. The roots of seedlings in PAW group grow lateral roots. This study provides new ideas and experimental evidence for PAW plant culture research and has a guiding significance for leguminous plant breeding. [ABSTRACT FROM AUTHOR]

In this study, a direct-current multineedle-plate corona discharge with different parameters was used to treat Ammopiptanthus mongolicus (Maxim. ex Kom. Cheng f.) seeds and study the effect of corona discharge physicochemical etching on these seeds. Results showed that the surface of the seed coat of A. mongolicus had wind erosion after corona discharge treatment, a large number of small ravines were generated and the surface crack of the seed coat was serious. Analysis of Fourier transform infrared spectroscopy revealed that the hydrophilic functional groups increased and corona discharge changed the chemical structure of A. mongolicus seed coat. The apparent contact angle decreased significantly from 99.82° ± 4.86° to 60.11° ± 8.44°, suggesting that corona discharge could significantly improve the hydrophilicity of A. mongolicus seeds. All the corona discharge treatment groups had seed germination at 24 h, whilst the control group had zero germination. This finding suggested that corona discharge treatment could significantly affect the structure and properties of A. mongolicus seed coat, improve the seed hydrophilicity and water absorption rate and promote the germination and growth of A. mongolicus seeds. This study provided ideas and experimental data support for the analysis of the mechanism of corona discharge biotechnology and seed-surface modification. [ABSTRACT FROM AUTHOR]