Inactivation Efficacy Research Articles

Characterization of anti-TMV indole alkaloid and isocoumarin derivatives from Aspergillus versicolor YNCA0363

BackgroundTobacco mosaic virus (TMV) is a harmful plant pathogen that causes a decline in the quality and yield of many economic crops. Natural products are important potential sources of biopesticides for the prevention and treatment of TMV. This study focuses on the discovery of anti-TMV active compounds from Aspergillus versicolor and investigates their activities against TMV.ResultsIn this study, four isocoumarins 7-methoxy-3-(2-oxopropy)-5-hydroxymethyl-isocoumarin (1), 7-methyl-3-(2-oxopropy)-5-hydroxymethyl-isocoumarin (2), oryzaein A (4) and oryzaein B (5), two indole alkaloids aspergilline F (6) and aspergilline G (7), and one indole alkaloid and isocoumarin hybrid aspergillactone A (3) were isolated from Nicotiana tabacum-derived A. versicolor YNCA0363. Among them, compounds 1–3 are new isolates, compound 3 represents the first example of indole alkaloid and isocoumarin connected by C(12)-N(1′) bond. The inactivation efficacies for compounds 1, 2 and 3 were 58.9, 43.8 and 52.6% at the concentration of 50 μg/mL, respectively, which were significantly higher than that of positive control, ningnanmycin. The protective effects of these three compounds ranged from 48.6 to 62.3%, which were significantly higher than that of positive control. At the same time, the content of TMV-CP was also significantly lower than that of positive control, and compound 1 was the lowest. The curative efficacy for compound 1 was also much better than that of positive control. Transmission electron microscopy (TEM) showed that compound 1 could directly destroy viral particles into small fragments. The results of molecular docking showed that the binding ability of compounds 1, 3, 2 to TMV-CP protein decreased in turn, which was consistent with the results of activities assays.ConclusionCompounds 1–3 from A. versicolor showed potent antiviral activities against TMV including inactivation, protective and curative effects. Compound 1 can directly destroy the virus particles to achieve the effect of anti-TMV. In addition, compounds 1–3 can bind to TMV-CP protein in molecular docking experiments. The above experimental results show that TMV-CP was an important target for active indole alkaloid and isocoumarin derivatives to fracture TMV particle. The results provided evidence that indole alkaloid and isocoumarin derivatives from A. versicolor have the potential to control TMV.Graphical

Disinfection efficiency of chlorine dioxide and peracetic acid against MNV-1 and HAV in simulated soil-rich wash water

Wash water from fresh vegetables and root vegetables is an important vehicle for foodborne virus transmission. However, there is lack of assessing rapid viral inactivation strategies in wash water characterized by a high soil content at the post-harvest stage. Considering the significance of food safety during the washing stage for fresh and root vegetable produce prior to marketing, we assessed the inactivation efficacy by using chlorine dioxide (ClO2) and peracetic acid (PAA) against a surrogate of human norovirus (murine norovirus 1, MNV-1) and hepatitis A virus (HAV), in wash water containing black soil and clay loam. The results indicated that MNV-1 and HAV were reduced to the process limit of detection (PLOD), with reductions ranging from 4.89 to 6.35 log10 PFU, and 4.63 to 4.96 log10 PFU when treated with ClO2 at 2.5 ppm for 10 mins. Comparatively, when treated with 500 ppm of PAA for 10 mins, MNV-1 and HAV were maximum reduced to 1.75 ± 0.23 log10 PFU (4.50 log10 PFU reduction) and 2.13 ± 0.12 log10 PFU (2.72 log10 PFU reduction). This demonstrated the efficacy of ClO2 in eliminating foodborne viruses in soil-rich wash water. When we validated the recovery of the virus from two types of wash water, the pH (9.24 ± 0.33 and 5.95 ± 0.05) had no impact on the recovery of MNV-1, while the recovery of HAV was less than 1 %. By adjusting the pH to a neutral level, recovery of HAV and its RNA levels was increased to 15.94 and 3.89 %. Thus, this study emphasized the critical role of pH in the recovery of HAV from the complex soil-rich aqueous environment, and the efficacy of ClO2 serving as a pivotal reference for the development of control strategies against foodborne viruses in the supply chain of fresh and root vegetables.

Impacts of Surface Characteristics and Dew Point on the Blue-Light (BL405) Inactivation of Viruses.

The increased prevalence of multidrug-resistant organisms (MDROs), healthcare associated infections (HAIs), and the recent COVID-19 pandemic has caused the photoinactivation industry to explore alternative wavelengths. Blue light (BL405) has gained significant interest as it is much less harmful to the skin and eyes than traditional germicidal wavelengths; therefore, in theory, it can be used continuously with human exposure. At present, the viricidal effects of BL405 are largely unknown as the literature predominately addresses bacterial disinfection performed with this wavelength. This work provides novel findings to the industry, reporting on the virucidal effects of BL405 on surfaces. This research utilizes three surfaces: ceramic, PTFE, and stainless steel. The efficacy of BL405 inactivation varied by surface type, which was due to surface characteristics, such as the contact angle, porosity, zeta potential, and reflectivity. Additionally, the effect of the dew point on BL405 inactivation efficacy was determined. This research is the first to study the effects of the dew point on the virucidal effectiveness of BL405 surface inactivation. The effects of the dew point were significant for all surfaces and the control experiments. The high-dew-point conditions (18 °C) yielded higher levels of BL405 inactivation and viral degradation for the experiments and controls, respectively.

Inactivation efficacy and mechanisms of wavelength-specific UV sources for various strains of Legionella pneumophila serogroup 1

Infections of Legionnaires' disease in the United States caused by Legionella have increased ninefold between the years 2000–2018. Legionella harbored in biofilms or inside amoeba within premise plumbing can be more resistant to disinfectants, thus causing treatment challenges. Ultraviolet-light emitting diodes (UV-LEDs) are an emerging water disinfection technology with several advantages over conventional UV lamps. In this study, we evaluated the effects of UV-LEDs (255, 265, and 285 nm), a low-pressure (LP) mercury UV lamp (254 nm), and a bandpass filtered medium-pressure (MP) mercury UV lamp (220 nm) on properties and inactivation of three strains of L. pneumophila serogroup 1. The UV-LEDs emitting at 255 and 265 nm showed greater inactivation performance against all the strains compared to the UV-LED at 285 nm and the LP UV lamp at 254 nm. Our results showed that strains of the same serogroup exhibited different UV sensitivities. Analyses of DNA and protein damage revealed that UV exposure using 254, 255, and 265 nm predominantly causes DNA damage, while protein damage is predominant at 220 nm. Both DNA and protein damage were observed at 285 nm, but the extent of DNA damage was relatively less significant compared to the other wavelengths. Electric energy consumption analysis showed that water treatment using UV-LEDs is currently unsatisfactory compared to conventional LP UV lamps due to the mediocre wall plug efficiency (WPE) of UV-LEDs. However, recent studies indicate that the WPE of UV-LEDs is continuously improving. Overall, our study highlights that UV-LEDs are a promising technology for inactivating waterborne pathogens and have the potential to replace existing UV mercury lamps for water disinfection applications.

Hydrocinnamic acid and perillyl alcohol are effective against Escherichia coli biofilms when used alone and combined with antibiotics.

The use of phytochemicals to improve the effectiveness of antibiotics is a promising strategy for the development of novel antimicrobials. In this study, the antibiofilm activity of perillyl alcohol and hydrocinnamic acid, both phytochemicals present in several plants, and two antibiotics from different classes (amoxicillin and chloramphenicol) was tested, alone and in combination, against Escherichia coli. Each molecule was tested at the minimum inhibitory concentration (MIC), 5×MIC, and 10×MIC, and characterized concerning biomass removal, metabolic inactivation, and cellular culturability. The highest percentages of metabolic inactivation (88.5% for 10×MIC) and biomass reduction (61.7% for 10×MIC) were obtained with amoxicillin. Interestingly, for 5×MIC and 10×MIC, phytochemicals provided a total reduction of colony-forming units (CFUs). Dual and triple combinations of phytochemicals and antibiotics (at MIC and 5×MIC) demonstrated high efficacy in metabolic inactivation, moderate efficacy in terms of biomass reduction, and total reduction of cellular culturability for 5×MIC. The results demonstrated the antibiofilm potential of phytochemicals, highlighting the advantage of phytochemical/antibiotic combinations for biofilm control.

A review on plasma-activated water and its application in the meat industry.

Meat is a nutritious food with a short shelf life, making it challenging to ensure safety, quality, and nutritional value. Foodborne pathogens and oxidation are the main concerns that lead to health risks and economic losses. Conventional approaches like hot water, steam pasteurization, and chemical washes for meat decontamination improve safety but cause nutritional and quality issues. Plasma-activated water (PAW) is a potential alternative to thermal treatment that can reduce oxidation and microbial growth, an essential factor in ensuring safety, quality, and nutritional value. This review explores the different types of PAW and their physiochemical properties. It also outlines the reaction pathways involved in the generation of short-lived and long-lived reactive nitrogen and oxygen species (RONS) in PAW, which contribute to its antimicrobial abilities. The review also highlights current studies on PAW inactivation against various planktonic bacteria, as well as critical processing parameters that can improve PAW inactivation efficacy. Promising applications of PAW for meat curing, thawing, and decontamination are discussed, with emphasis on the need to understand how RONS in PAW affect meat quality. Recent reports on combining PAW with ultrasound, mild heating, and non-thermal plasma to improve inactivation efficacy are also presented. Finally, the need to develop energy-efficient systems for the production and scalability of PAW is discussed for its use as a potential meat disinfectant without compromising meat quality.

Meta-Aerogel Electric Trap Enables Instant and Continuable Pathogen Killing in Face Masks.

The tremendous menace of the COVID-19 pandemic has underscored the urgency for antipathogen masks to stop the transmission of airborne infectious diseases. Most prevailing antipathogen masks manifest a slower sterilization rate that lags behind the pathogen momentum traversing the masks, thereby engendering an elevated susceptibility to infection. Here we tailor nanofibrous meta-aerogel electric traps, 3D-assembled from self-knotted carbon nanotube networks in an all rigid nanofibrous skeleton. This superior configuration revolves around the creation of numerous "dielectrophoretic-aerodynamic grippers", which are capable of directional manipulation of microbes toward the region of the lethal intensive electric field. Based on this, we present a disinfection unit comprising a pair of aerogel electrodes that demonstrate a rapid killing rate (>99.99% biocidal efficacy within 0.016 s) and long-term durability (12 h of continuous operation). Additionally, a microbutton lithium cell is employed as a power supply to fabricate an antipathogen face mask with this disinfection unit, which exhibits superior pathogen inactivation efficacy compared to commercial masks. This scalable biocidal protective equipment holds great potential for use in emergency medical services.

Efficacy of Pectobacterium carotovorum subsp. carotovorum inactivation using ultraviolet C light-emitting diodes: Investigation of inactivation efficacy toward planktonic and biofilm cells on the stainless steel surfaces of cutting machines

The presence of Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) in kimchi cabbage (Brassica rapa L. subsp. pekinensis) negatively influences kimchi quality. Accordingly, inactivation processes to effectively control spoilage caused by plant bacteria, including P. carotovorum, are crucial for extending the shelf life of kimchi. In this regard, ultraviolet C light-emitting diode (UVC-LED) technologies are increasingly attracting attention as non-thermal and non-contact sterilization technologies and are also considered as alternatives to chemical disinfectants. In this study, we investigated the efficacy of the inactivation of P. carotovorum planktonic and biofilm cells that cause cabbage soft rot disease using the UVC-LED treatment technology as a potential disinfection method for a safe kimchi manufacturing process. A biofilm was formed on the surface of a stainless-steel cutter knife using the recommended CDC biofilm reactor system and thereafter, exposed to a range of UVC-LED intensities. Our results indicated that P. carotovorum planktonic and biofilm cells to UVC-LED irradiation at 9.0 mJ/cm2 resulted in >5.0 and >2.0 log10 inactivation, respectively. Additionally, the P. carotovorum planktonic and biofilm cell inactivation kinetics fitted the non-linear reduction curve. The UVC-LED treatment was also found to be highly efficient in eliminating planktonic cells, showing consistency with the Weibull and Weibull tailing models for planktonic cells.

Plasma-activated water for inactivation of Salmonella Typhimurium avirulent surrogate: Applications in produce and shell egg and understanding the modes of action

Plasma-activated water (PAW) is gaining interest as a novel sanitizer for foods. However, the sanitizing efficacy of PAW varies under different conditions, and its modes of action and impacts on food quality need further investigation for it to be applied in the food industry. This study evaluated the inactivation efficacy of PAW against a Salmonella Typhimurium avirulent surrogate, investigated the underlying mechanisms, and assessed the impacts of PAW on the safety and quality of cherry tomatoes and shell eggs. PAW was effective in inactivating S. Typhimurium in a planktonic state (1.5–5.8 log CFU reduction in 2–5 min) and on the food surface (>5 log CFU reduction in 5 min). PAW prepared with deionized water vs. tap water did not differ significantly in sanitizing efficacy. Various reactive oxygen and nitrogen species (RONS) contributed to the antimicrobial property of PAW, with nitric oxide playing the most significant role. The acidic nature of PAW might synergistically affect bacteria by disrupting cell membrane and enhancing RONS permeation. PAW did not modify the visual appearance and internal pH of the treated foods. This study demonstrates that PAW has the potential to be applied as a novel sanitizer for fresh produce and egg washing.

The Impact of Low-Level Benzalkonium Chloride Exposure on Staphylococcus spp. Strains and Control by Photoinactivation.

Exposure of bacteria to low concentrations of biocides can facilitate horizontal gene transfer, which may lead to bacterial adaptive responses and resistance to antimicrobial agents. The emergence of antibacterial resistance not only poses a significant concern to the dairy industry but also adds to the complexity and cost of mastitis treatment. This study was aimed to evaluate how selective stress induced by benzalkonium chloride (BC) promotes antibiotic non-susceptibility in Staphylococcus spp. In addition, we investigated the efficacy of photodynamic inactivation (PDI) in both resistant and susceptible strains. The study determined the minimum inhibitory concentration (MIC) of BC using the broth microdilution method for different Staphylococcus strains. The experiments involved pairing strains carrying the qacA/qacC resistance genes with susceptible strains and exposing them to subinhibitory concentrations of BC for 72 h. The recovered isolates were tested for MIC BC and subjected to disc diffusion tests to assess changes in susceptibility patterns. The results demonstrated that subinhibitory concentrations of BC could select strains with reduced susceptibility and antibiotic resistance, particularly in the presence of S. pasteuri. The results of PDI mediated by toluidine blue (100 µM) followed by 60 min irradiation (total light dose of 2.5 J/cm2) were highly effective, showing complete inactivation for some bacterial strains and a reduction of up to 5 logs in others.

Evaluation of the Inactivation Efficacy of Four Disinfectants for Feline Parvovirus Derived from Giant Panda.

Feline panleukopenia (FPL) is a highly contagious acute infectious disease caused by feline parvovirus (FPV). FPV has also been found in giant pandas with clinical signs of vomiting and mild diarrhea, posing a threat to this vulnerable species. Cleaning and disinfection may be one of the most efficacious ways to prevent FPV spread in the habitat of giant pandas. This study evaluated the inactivation effect of peracetic acid (PAA), povidone-iodine (PVP-I), glutaral and deciquam solution (JM) and Virkon S. The tissue culture infective dose (TCID50) assay indicated that the virus may be totally inactivated by JM, PAA and Virkon S. Meanwhile, the hemagglutination (HA) assay showed a high inactivation efficiency of PAA and Virkon S. The analysis of Western blot revealed that PAA, Virkon S and JM can inhibit the structural protein synthesis. Taken together, our findings demonstrated that PAA could rapidly and efficiently inactivate FPV, representing an efficacious disinfectant for FPV control.

Efficacy of cold plasma-activated water as an environmentally friendly sanitizer in egg washing

Eggs in the United States are typically washed using chemical sanitizers such as quaternary ammonia (QA) or chlorine. Such treatments generate wash water, which could be potentially hazardous to the environment. A novel, nonthermal sanitization technique for washing shell eggs using cold plasma-activated water (PAW) was investigated in this study. The inactivation efficacy of PAW on Klebsiella michiganensis and the impact of PAW on the cuticle of the eggshell and shell strength were tested in comparison to QA. Washing inoculated eggs with PAW and QA achieved a similar microbial reduction (>5.28 log CFU/egg). Colorimetric analysis showed that ∆E-value for PAW-treated eggs was significantly lower than QA-treated eggs, suggesting higher cuticle coverage in eggs treated with PAW. The texture analysis to test for shell egg strength indicated that washing eggs with PAW did not affect the structural integrity of the eggshell when compared to eggs washed with QA. According to this study, PAW has the potential as an alternative to commercial sanitizers like QA in the egg-washing industry. PAW does not detrimentally impact shell strength or cuticle coverage and provides similar microbial reduction efficacy.

Investigation of the efficacy and safety of retinal inactivation as a treatment for amblyopia in cats.

Deprivation of normal vision early in postnatal development elicits modifications of neural circuitry within the primary visual pathway that can cause a severe and intractable vision impairment (amblyopia). In cats, amblyopia is often modeled with monocular deprivation (MD), a procedure that involves temporarily closing the lids of one eye. Following long-term MD, brief inactivation of the dominant eye's retina can promote recovery from the anatomical and physiological effects of MD. In consideration of retinal inactivation as a viable treatment for amblyopia it is imperative to compare its efficacy against conventional therapy, as well as assess the safety of its administration. In the current study we compared the respective efficacies of retinal inactivation and occlusion of the dominant eye (reverse occlusion) to elicit physiological recovery from a prior long-term MD in cats. Because deprivation of form vision has been associated with development of myopia, we also examined whether ocular axial length or refractive error were altered by a period of retinal inactivation. The results of this study demonstrate that after a period of MD, inactivation of the dominant eye for up to 10 days elicited significant recovery of visually-evoked potentials that was superior to the recovery measured after a comparable duration of reverse occlusion. After monocular retinal inactivation, measurements of ocular axial length and refractive error were not significantly altered from their pre-inactivation values. The rate of body weight gain also was not changed during the period of inactivation, indicating that general well-being was not affected. These results provide evidence that inactivation of the dominant eye after a period of amblyogenic rearing promotes better recovery than eye occlusion, and this recovery was achieved without development of form-deprivation myopia.

Wavelength dependence of ultraviolet light inactivation for SARS-CoV-2 omicron variants

Ultraviolet (UV) irradiation offers an effective and convenient method for the disinfection of pathogenic microorganisms. However, UV irradiation causes protein and/or DNA damage; therefore, further insight into the performance of different UV wavelengths and their applications is needed to reduce risks to the human body. In this paper, we determined the efficacy of UV inactivation of the SARS-CoV-2 omicron BA.2 and BA.5 variants in a liquid suspension at various UV wavelengths by the 50% tissue culture infection dose (TCID50) method and quantitative polymerase chain reaction (qPCR) assay. The inactivation efficacy of 220 nm light, which is considered safe for the human body, was approximately the same as that of health hazardous 260 nm light for both BA.2 and BA.5. Based on the inactivation rate constants determined by the TCID50 and qPCR methods versus the UV wavelength, the action spectra were determined, and BA.2 and BA.5 showed almost the same spectra. This result suggests that both variants have the same UV inactivation characteristics.

Removal of the red tide dinoflagellate Cochlodinium polykrikoides using chemical disinfectants

For decades, red tide control has been recognized as necessary for mitigating financial damage to fish farms. Chemical disinfectants, frequently used for water disinfection, can reduce the risk of red tides on inland fish farms. This study systematically evaluated four different chemical disinfectants (ozone (O3), permanganate (MnO4−), sodium hypochlorite (NaOCl), and hydrogen peroxide (H2O2)) for their potential use in inland fish farms to control red tides by investigating their (i) inactivation efficacy regarding C. polykrikoides, (ii) total residual oxidant and byproduct formation, and (iii) toxicity to fish. The inactivation efficacy of C. polykrikoides cells by chemical disinfectants from highest to lowest followed the order of O3 > MnO4− > NaOCl > H2O2 for different cell density conditions and disinfectant doses. The O3 and NaOCl treatments generated bromate as an oxidation byproduct by reacting with bromide ions in seawater. The acute toxicity tests of the disinfectants for juvenile red sea bream (Pagrus major) showed that 72-h LC50 values were 1.35 (estimated), 0.39, 1.32, and 102.61 mg/L for O3, MnO4−, NaOCl, and H2O2, respectively. Considering the inactivation efficacy, exposure time of residual oxidants, byproduct formation, and toxicity toward fish, H2O2 is suggested as the most practical disinfectant for controlling red tides in inland fish farms.

Evaluation of plasma-activated water: Efficacy, stability, physicochemical properties, and mechanism of inactivation against Escherichia coli

In this study, plasma-activated water (PAW) was prepared by discharge below the surface of sterile distilled water. In addition to physicochemical properties, the bactericidal effect and mechanism of action of PAW were studied using Escherichia coli as the target microorganism. The plasma treatment would cause an increase in the redox potential (ORP), electrical conductivity (EC), NO3− and NO2− content, and a decrease in the pH of the water. At the same time, the sterilization effect of PAW on E. coli was progressively stronger with both discharge and immersion time, up to a maximum of 4.25 log CFU/mL. In addition, the EC, NO3− and NO2− content, as well as the bactericidal efficacy of PAW decreased with increasing storage time. The properties and bactericidal effects did not change significantly after PAW thawing (p > 0.05). Finally, proteomics techniques were used to identify and classify the differential proteins before and after PAW treatment. PAW treatment induced a stress response in E. coli. Differential expression proteins of biological processes including the metabolism of phosphorus-containing compounds and the cellular response to stimuli, as well as various binding-related and membrane structure-related, were induced.

Synthesis and photodynamic antimicrobial chemotherapy against multi-drug resistant Proteus mirabilis of ornithine-porphyrin conjugates in vitro and in vivo.

For the treatment of bacterial infections, photodynamic antimicrobial chemotherapy (PACT) has the advantage of circumventing multi-drug resistance. In this work, new cationic photosensitizers against multi-drug resistant Proteus mirabilis (MRPM) were designed and synthesized by the conjugation of amino phenyl porphyrin with basic amino acid L-ornithine. Their photoinactivation efficacies against MRPM in vitro were reported and include the influence of laser energy, uptake, MIC and MBC, dose-dependent photoinactivation effects, membrane integrity, and fluorescence imaging. The PACT in vivo was evaluated using a wound mouse model infected by MRPM. Photosensitizer 4d displayed high photo inactivation efficacy against MRPM at 7.81 μM under illumination, and it could accelerate wound healing via bactericidal effect. These ornithine-porphyrin conjugates are potential photosensitizers for PACT in the treatment of MRPM infection.

Advances in efficacy enhancement of photosensitizer-mediated photodynamic antimicrobial chemotherapy

The fight against pathogenic microorganisms has in recent decades been met with fierce setbacks owing to the antimicrobial resistance phenomenon. Conventional antimicrobials have thus weakened in their effectiveness against microbes, calling for the development of innovative strategies to combat the emerging global health crisis. A promising therapy for filling this gap is photodynamic antimicrobial chemotherapy which destroys microorganisms by making use of the combined action of a photosensitizer, light, and oxygen. The modality inactivates a wide range of pathogens, including bacteria, fungi, protozoa, and viruses. Of greater interest in photodynamic antimicrobial chemotherapy is the ability to destroy resistant strains of microbes without encouraging selection for resistance genes, thus immensely contributing to the fight against antimicrobial resistance. Different PSs vary in their microbial inactivation efficacies. Therefore, various structural modification approaches are being adopted to improve their respective activities. In this paper, recent studies focusing on strategies employed to improve the effectiveness and efficacies of PSs used in photodynamic antimicrobial chemotherapy are reviewed.

Inactivation effect of Staphylococcus aureus and application on fresh-cut pineapples by plasma-activated tartaric acid

The insufficient antibacterial effect of organic acids accelerates the desire for new decontamination approaches. This study aimed to investigate the combined inactivation efficacy of plasma-activated water (PAW) and organic acids on Staphylococcus aureus (S. aureus) as well as the underlying mechanism. The present study showed that the PAW or tartaric acid (TA) treatment led to an approximately 1 log CFU/mL decrease of S. aureus cells, while a higher reduction of 5.42 log CFU/mL was observed after the combined treatment (PAW plus TA). Scanning electron microscope and propidium iodide staining analysis showed that the structure and activity of most bacteria were not changed. The PAW and TA treatments caused modest oxidative damage to the cell membrane, while the damage to defense function occurred in S. aureus after the combined treatment, as indicated by the lower ROS level and higher MDA content compared with the control. Meanwhile, the combined treatment caused 2.7 and 4.1 log CFU/g reductions of S. aureus cells in a fresh-cut pineapple model at 4 °C and 25 °C. This approach could maintain most quality attributes of fresh-cut pineapples at an acceptable level and extend their shelf life. The results suggest that the combination of PAW and TA could be considered a novel technology for bacterial inactivation in fresh-cut products.

A Practical Bacterial Biodosimetry Procedure to Assess Performance of Lab-Scale Flow-through Ultraviolet Water Disinfection Reactors

Biodosimetry can be used to estimate the fluence of a reactor by determining its ability to inactivate a challenge organism. Especially for small-scale flow-through reactors, inconsistent procedures are reported for bacterial cells. This study aims to develop a standardized, simple procedure for bacterial biodosimetry in flow-through UV systems with relevant biofilm-forming bacteria, to evaluate biofouling control by UV. In particular, the challenge organism, the type of experimental setup, and the execution of single steps during biodosimetry with bacterial cells can cause largely deviating results. Since previous work was restricted to model organisms, which are not relevant for biofouling, we critically re-evaluated all reported steps for the biofilm forming Aquabacterium citratiphilum and identified three main factors for biodosimetry reproducibility in flow-through systems: Protractions of cells from controls without UV can heavily impact inactivation efficacy but can be reduced by ordering samples by decreasing fluence. Further, to avoid photorepair, samples must be processed under red light only. Lastly, biofilm forming bacteria can strongly adsorb on plastic labware, which requires counter measures in the form of special labware and the addition of surfactants. Overall, the developed protocol provides a biodosimetry standardization for bacterial cells of flow-through systems, facilitating reproducibility and transferability of results between studies that use bacterial cells as a challenge organism.