Evaluation of Cylindrical Asymmetric Surface Dielectric Barrier Discharge Actuators for Surface Decontamination and Mixing

Surface dielectric barrier discharge (SDBD) was used to evaluate cylindrical plasma actuators for inactivation of Salmonella enterica. A cylindrical SDBD configuration was evaluated to determine if the inherent induced body force could be leveraged to impel plasma species, such as reactive oxygen and nitrogen species (RONS), as an apparatus to sterilize surfaces. The cylindrical structure is evaluated in this study to observe whether an increase in mixing is possible to efficiently distribute the plasma species, thereby improving bacterial inactivation efficiency. The increase in induced airflow of SDBD actuators with increased numbers of electrodes correlates with increased bacterial inactivation. These results suggest that improving the particle velocity, airflow mixing tendencies, and plasma volume for the same power inputs (same net power to the actuators) results in increased surface decontamination efficiency.

Photochemical treatment of organic constituents and bacterial pathogens from synthetic slaughterhouse wastewater by combining vacuum-UV and UV-C

The reduction and degradation of total organic carbon (TOC) and bacteria inactivation efficiency using Vacuum-Ultraviolet (VUV) oxidation process Ultraviolet-C (UV-C) photolytic process, and their combination (UV-C/VUV and VUV/UV-C) from synthetic slaughterhouse wastewater was investigated. TOC removal rates achieved during continuous mode operation were 6.2%, 5.5%, 5.8%, and 6.1%, respectively. In a second stage, H₂O₂ was added to both processes, UV-C/H₂O₂ and VUV/H₂O₂, and it was found that TOC removal rates were increased twice as much during continious flow operation to 10.8% and 12.2%, respectively. The optimum molar ration of H₂O₂/TOC was found to be 2.5 and 1.5 for each process respectively. Finally, it was observed that all photochemical processes achieved over 99.999% (five logs) of bacteria inactivation in a short period of irradiation time, 27.6 sec.

Photochemical treatment of organic constituents and bacterial pathogens from synthetic slaughterhouse wastewater by combining vacuum-UV and UV-C

The reduction and degradation of total organic carbon (TOC) and bacteria inactivation efficiency using Vacuum-Ultraviolet (VUV) oxidation process Ultraviolet-C (UV-C) photolytic process, and their combination (UV-C/VUV and VUV/UV-C) from synthetic slaughterhouse wastewater was investigated. TOC removal rates achieved during continuous mode operation were 6.2%, 5.5%, 5.8%, and 6.1%, respectively. In a second stage, H₂O₂ was added to both processes, UV-C/H₂O₂ and VUV/H₂O₂, and it was found that TOC removal rates were increased twice as much during continious flow operation to 10.8% and 12.2%, respectively. The optimum molar ration of H₂O₂/TOC was found to be 2.5 and 1.5 for each process respectively. Finally, it was observed that all photochemical processes achieved over 99.999% (five logs) of bacteria inactivation in a short period of irradiation time, 27.6 sec.

Inactivation of Indigenous Microorganisms and Salmonella in Korean Rice Cakes by In-Package Cold Plasma Treatment

The antimicrobial effects of in-package cold plasma (CP) treatment on Korean rice cakes (KRC) were evaluated. The CP treatment (25 kV) inactivated indigenous mesophilic aerobic bacteria by 0.8–1.0 log CFU/g, irrespective of the position of KRC in the package. The addition of a shaking step during CP treatment increased the reduction in microbes by ~1 log CFU/g. The microbial inactivation efficiency increased significantly when the treatment time increased from 1 to 3 min. Microbial inactivation activity was highest for packages containing eight rice cakes. The optimized CP treatment achieved a 2.0 ± 0.1 log CFU/g reduction in indigenous bacteria. In addition, the optimum CP treatment inactivated indigenous yeast and molds and Salmonella in KRC by 1.7 ± 0.1 log CFU/g and 3.9 ± 0.3 log CFU/g, respectively. No significant changes in color and firmness were observed, and the surface temperature of KRC did not exceed 22 °C after CP treatment. Moreover, CP treatment damaged the cellular membrane of Salmonella, mainly by inducing lipid peroxidation. This study demonstrates the potential use of in-package CP treatment for the non-thermal microbial inactivation of KRC.

CRISPR-Cas9 gene editing and rapid detection of gene-edited mutants using high-resolution melting in the apple scab fungus, Venturia inaequalis

BackgroundScab, or black spot, caused by the filamentous fungal pathogen Venturia inaequalis, is the most economically important disease of apple (Malus x domestica) worldwide. To develop durable control strategies against this disease, a better understanding of the genetic mechanisms underlying the growth, reproduction, virulence and pathogenicity of V. inaequalis is required. A major bottleneck for the genetic characterization of V. inaequalis is the inability to easily delete or disrupt genes of interest using homologous recombination. Indeed, no gene deletions or disruptions in V. inaequalis have yet been published. Recently, CRISPR-Cas9 has emerged as an efficient tool for gene editing in filamentous fungi. With this in mind, we set out to establish CRISPR-Cas9 as a gene editing tool in V. inaequalis.ResultsWe showed that CRISPR-Cas9 can be used for gene inactivation in the apple scab fungus. As a proof of concept, we targeted the melanin biosynthesis pathway gene trihydroxynaphthalene reductase (THN), which has previously been shown to result in a light-brown colony phenotype when transcriptionally silenced using RNA interference. Using one of two CRISPR-Cas9 single guide RNAs (sgRNAs) targeted to the THN gene, delivered by a single autonomously replicating Golden Gate-compatible plasmid, we were able to identify six of 36 stable transformants with a light-brown phenotype, indicating an ~16.7% gene inactivation efficiency. Notably, of these six THN mutants, five had an independent mutation. As part of our pipeline, we also report a high-resolution melting (HRM) curve protocol for the rapid detection of CRISPR-Cas9 gene-edited mutants of V. inaequalis. This protocol identified a single base pair deletion mutation in a sample containing only 5% mutant genomic DNA, indicating high sensitivity for mutant screening.ConclusionsIn establishing CRISPR-Cas9 as a tool for gene editing in V. inaequalis, we have provided a strong starting point for studies aiming to decipher the function of genes associated with the growth, reproduction, virulence and pathogenicity of this fungus. The associated HRM curve protocol will enable CRISPR-Cas9 transformants to be screened for gene inactivation in a high-throughput and low-cost manner, which will be particularly powerful in cases where the CRISPR-Cas9-mediated gene inactivation efficiency is low.

Applicability of infectivity assay for the quantification of infectious human adenovirus genotype 5 in UV-irradiated wastewater

The use of infectivity assays in domestic wastewater samples are limited because of the concerns on cytotoxicity to host cells, thus, the UV inactivation efficiency of human adenoviruses (HAdVs) in wastewater remains unclear. In this study, a human adenovirus genotype five (HAdV-5) host cell line (A549 cells) was incubated with wastewater at varied dilutions from 1:1.5 to 1:4 (the ratio of wastewater to a mixture of wastewater and the cell culture medium) and the cytotoxicity was assessed by the cell morphology and viability. No change was observed in either cell viability or morphology in comparison with control samples, even at lowest dilution of 1:1.5, indicating the dilution allowed infectivity assays. The minimal degree of dilution to avoid cytotoxicity may differ with different water matrix. Consequently, the technique was applied to quantify spiked HAdV-5 after the UV disinfection of wastewater. A significant increase in UV disinfection efficiency was noted in wastewater and hydroxyl radicals (OH•) produced by the photosensitization of dissolved organic matter were suggested to be responsible for the enhancement. This study indicated that dilution can be a simple solution to avoid cytotoxicity, and UV inactivation may be enhanced in wastewater due to OH• radicals produced by UV radiation.

Urine treatment by solar disinfection for agriculture reuse purpose in a poor rural context: case of Burkina Faso

The study aimed to reduce the storage time of urine treatment and assess the quality of treated urine following the Solar DISinfection (SODIS) method. Microbiological analyses were performed on urine samples taken before each sunlight exposure, between 10am and 4pm at a frequency of 1 h, during which temperature was measured in PET bottles (1.5 L). The initial concentrations of Escherichia coli (E. coli) and Salmonella in unstored urine were 106 and 103 CFU/100 mL respectively. The combined effect of temperature and UV radiation increased inactivation efficiency of E. coli at 5 log units. On the other hand, 98% of Salmonella were inactivated in less than 3 h of continuous exposure between 12am and 3pm with temperature varying between 50 and 65 °C in PET bottles. The k values showed that the inactivation rate of Salmonella tested was accelerated when the temperature was above 50 °C. Then, the results indicated that the first-order exponential decay model was the best method to predict the inactivation of Salmonella in urine by SODIS. General results showed that after 3 days of exposure to sunlight, urine collected via eco-toilet becomes bacteriologically sanitized and therefore can be used in agriculture.