Mechanism of microbial spore inactivation through electromagnetic radiations:a review

Spores are the biological structures formed out of sporulation from vegetative cells in adverse conditions.Being tolerant to many extreme environment and conditions,they escape and survives critical processing steps in the food industry that poses food and health safety problems,as is evident from the increase in reports of food-bome outbreaks due to spore-fomers.Electromagnetic radiation(EM)is used for rapid decontamination and sterilization purposes in the food industry.Many studies have reported a greater reduction in spore population upon irradiation with EM rays due to its impact on genomic material and other components of spores that destabilises overall structue and brings clonogenic death However,there is scattered literature regarding the mechanism of its inactivation and resistance against such damage.This review attempts to concisely evaluate the potential of electromagnetic radiations in spore inactivation and details its mechanism through a collective study of scientific results and repouts.It also briefs about the process of sporulation,the structure of spores and the role of its components in the resistance of spores to damage.Many studies,which demonstrated that combining various EM treatments might be an effective way for inactivation of spores,were discussed in detail.

Multiple action sites of ultrasound on Escherichia coli and Staphylococcus aureus

Ultrasound,is thought to a potential non-thermal sterilization technology in food industry.However,the exact mechanisms underlying microbial inactivation by ultrasound still remain obscure.In this study,the action modes of ultrasound on both Gram-negative and Gram-positive microorganisms were estimated.From colony results,ultrasound acted as an irreversible effect on both Eshcerichia coli and Staphylococcus aureus without sublethal injury.The result in this study also showed that a proportion of bacteria subpopulation suffered from serious damage of intracellular components(e.g.DNA and enzymes)but with intact cell envelopes.We speculated that the inactivated effects of ultrasound on microbes might more than simply completed disruption of cell exteriors.Those microbial cells who had not enter the valid area of ultrasonic cavitation might be injected with free radicals produced by ultrasound and experienced interior injury with intact exterior structure,and others who were in close proximity to the ultrasonic wave field would be immediately and completely disrupted into debris by high power mechanic forces.These findings here try to provide extension for the inactivation mechanisms of ultrasound on microorganisms.

The interaction of an atmospheric pressure plasma jet using argon or argon plus hydrogen peroxide vapour addition with bacillus subtilis

This paper reports that an atmospheric pressure dielectric barrier discharge plasma jet, which uses argon or argon ＋ hydrogen peroxide vapour as the working gas, is designed to sterilize the bacillus subtilis. Compared with the pure argon plasma, the bacterial inactivation efficacy has a significant improvement when hydrogen peroxide vapour is added into the plasma jet. In order to determine which factors play the main role in inactivation, several methods are used, such as determination of optical emission spectra, high temperature dry air treatment, protein leakage quantification, and scanning electron microscope. These results indicate that the possible inactivation mechanisms are the synergistic actions of chemically active species and charged species.

Bacteria inactivation by sulfate radical:progress and non-negligible disinfection by-products

Sulfate radicals have been increasingly used for the pathogen inactivation due to their strong redox ability and high selectivity for electron-rich species in the last decade.The application of sulfate radicals in water disinfection has become a very promising technology.However,there is currently a lack of reviews of sulfate radicals inactivated pathogenic microorganisms.At the same time,less attention has been paid to disinfection by-products produced by the use of sulfate radicals to inactivate microorganisms.This paper begins with a brief overview of sulfate radicals’properties.Then,the progress in water disinfection by sulfate radicals is summarized.The mechanism and inactivation kinetics of inactivating microorganisms are briefly described.After that,the disinfection by-products produced by reactions of sulfate radicals with chlorine,bromine,iodide ions and organic halogens in water are also discussed.In response to these possible challenges,this article concludes with some specific solutions and future research directions.

Inactivation and risk control of pathogenic microorganisms in municipal sludge treatment:A review

The rapid global spread of coronavirus disease 2019(COVID-19)has promoted concern over human pathogens and their significant threats to public health security.The monitoring and control of human pathogens in public sanitation and health facilities are of great importance.Excessive sludge is an inevitable byproduct of sewage that contains human and animal feces in wastewater treatment plants(WWTPs).It is an important sink of different pollutants and pathogens,and the proper treatment and disposal of sludge are important to minimize potential risks to the environment and public health.However,there is a lack of comprehensive analysis of the diversity,exposure risks,assessment methods and inactivation techniques of pathogenic microorganisms in sludge.Based on this consideration,this review summarizes the control performance of pathogenic microorganisms such as enterovirus,Salmonella spp.,and Escherichia coli by different sludge treatment technologies,including composting,anaerobic digestion,aerobic digestion,and microwave irradiation,and the mechanisms of pathogenic microorganism inactivation in sludge treatment processes are discussed.Additionally,this study reviews the diversity,detection methods,and exposure risks of pathogenic microorganisms in sludge.This review advances the quantitative assessment of pathogenic microorganism risks involved in sludge reuse and is practically valuable to optimize the treatment and disposal of sludge for pathogenic microorganism control.

Response of bioaerosol cells to photocatalytic inactivation with ZnO and TiO_(2)impregnated onto Perlite and Poraver carriers

Bioaerosols are airborne microorganisms that cause infectious sickness,respiratory and chronic health issues.They have become a latent threat,particularly in indoor environment.Photocatalysis is a promising process to inactivate completely bioaerosols from air.However,in systems treating a continuous air flow,catalysts can be partially lost in the gaseous effluent.To avoid such phenomenon,supporting materials can be used to fix catalysts.In the present work,four photocatalytic systems using Perlite or Poraver glass beads impregnated with ZnO or TiO_(2)were tested.The inactivation mechanism of bioaerosols and the cytotoxic effect of the catalysts to^bioaeros^ls were studied.The plug flow photocatalytic reactor treated a bioaerosol flow of 460×10^(6)cells/m^(3)_(air)with a residence time of 5.7 s.Flow Cytometry(FC)was used to quantify and characterize bioaerosols in terms of dead,injured and live cells.The most efficient system was ZnO/Perlite with 72%inactivation of bioaerosols,maintaining such inactivation during 7.5 h due to the higher water retention capacity of Perlite(2.8 mL/gpcriite)in comparison with Poraver(1.5 mL/gperiite).However,a global balance showed that Ti0_(2)/Poraver system triggered the highest level of cytotoxicity to bioaerosols retained on the support after 96 h with 95%of dead cells.SEM and FC analyses showed that the mechanism of inactivation with ZnO was based on membrane damage,morphological cell changes and cell lysis;whereas only membrane damage and cell lysis were involved with Ti0_(2).Overall,results highlighted that photocatalytic technologies can completely inactivate bioaerosols in indoor environments.

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection:Recent overview and further trends

Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO2 is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO2 as a disinfecting agent, and the pathogen inactivation mechanism of CO2 treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO2 treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions（pressure, temperature, microorganism, water content, media …） suggest that most microorganisms are successfully inhibited under CO2 treatment. It will also be shown that the bacterial deaths under CO2 treatment can be explained by many different mechanisms.Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products（resulting from chlorination or ozone treatment）.