Antibacterial mechanism of kojic acid and tea polyphenols against Escherichia coli O157:H7 through transcriptomic analysis

Escherichia coli O157:H7 is one of the major foodborne pathogenic bacterial that cause infectious diseases in humans.The previous found that a combination of kojic acid and tea polyphenols exhibited better activity against E.coli O157:H7 than using either alone.This study aimed to explore responses underlying the antibacterial mechanisms of kojic acid and tea polyphenols from the gene level.The functional enrichment analysis by comparing kojic acid and tea polyphenols individually or synergistically against E.coli O157:H7 found that acid resistance systems in kojic acid were activated,and the cell membrane and genomic DNA were destructed in the cells,resulting in“oxygen starvation”.The oxidative stress response triggered by tea polyphenols inhibited both sulfur uptake and the synthesis of ATP,which affected the bacteria's life metabolic process.Interestingly,we found that kojic acid combined with tea polyphenols hindered the uptake of iron that played an essential role in the synthesis of DNA,respiration,tricarboxylic acid cycle.The results suggested that the iron uptake pathways may represent a novel approach for kojic acid and tea polyphenols synergistically against E.coli O157:H7 and provided a theoretical basis for bacterial pathogen control in the food industry.

Antibacterial Mechanism of Copper-bearing Antibacterial Stainless Steel against E.Coli

A preliminary study was made on the antibacterial mechanism of copper-bearing antibacterial stainless steels against E.coli through experiments of microbiology such as EDTA （ethylenediaminetetraacetic acid） complexing, DNA smearing and AFM （atomic force microscope） observation. It was measured that the antibacterial stainless steels showed excellent antibacterial functions with antibacterial rate to E.coli over 99.99%. The antibacterial rate was weak if the bacteria solution was complexed by EDTA, indicating that the copper ions play a dominant role in the antibacterial effect of the antibacterial stainless steels. The electrophoresis experiment did not show the phenomenon of DNA smearing for E.coli after contacting antibacterial stainless steels, which meant that DNA of E.coli was not obviously damaged. It was observed by AFM that the morphology of E.coli changed a lot after contacting antibacterial stainless steels, such as cell walls being seriously changed and lots of contents in the cells being leaked.

Different antibacterial mechanisms of titania nanotube arrays at various growth phases of E.coli

To clarify the antibacterial behavior at early adhesion,two titania nanotube(TNT)arrays were fabricated on polished commercially pure titanium(Ti),and the interaction mechanisms between TNT arrays and the model bacteria(Escherichia coli,E.coli)were investigated.The results show that TNT arrays exhibit a significant early antibacterial effect,which is highly related to the surface free energy and nano-topography.The underlying antibacterial mechanisms include:(1)the anti-initial-attachment effect at the lag phase(0−4 h);(2)the anti-proliferation and physical bactericidal effects at the logarithmic phase(4−12 h);(3)the reduced antimicrobial properties probably due to the overgrowth of bacteria on TNT arrays at the stationary phase(12 h and then).

Antibacterial mechanism with consequent cytotoxicity of different reinforcements in biodegradable magnesium and zinc alloys: A review

Benefits achieved by the biodegradable magnesium(Mg) and zinc(Zn) implants could be suppressed due to the invasion of infectious microbial, common bacteria, and fungi. Postoperative medications and the antibacterial properties of pure Mg and Zn are insufficient against biofilm and antibiotic-resistant bacteria, bringing osteomyelitis, necrosis, and even death. This study evaluates the antibacterial performance of biodegradable Mg and Zn alloys of different reinforcements, including silver(Ag), copper(Cu), lithium(Li), and gallium(Ga). Copper ions(Cu^(2+)) can eradicate biofilms and antibiotic-resistant bacteria by extracting electrons from the cellular structure. Silver ion(Ag^(+)) kills bacteria by creating bonds with the thiol group. Gallium ion(Ga^(3+)) inhibits ferric ion(Fe^(3+)) absorption, leading to nutrient deficiency and bacterial death. Nanoparticles and reactive oxygen species(ROS) can penetrate bacteria cell walls directly, develop bonds with receptors, and damage nucleotides. Antibacterial action depends on the alkali nature of metal ions and their degradation rate, which often causes cytotoxicity in living cells. Therefore, this review emphasizes the insight into degradation rate, antibacterial mechanism, and their consequent cytotoxicity and observes the correlation between antibacterial performance and oxidation number of metal ions.

Physicochemical properties and antibacterial mechanism of theabrownins prepared from different catechins catalyzed by polyphenol oxidase and peroxidase

Theabrownins(TBs)are the characteristic functional and quality components of dark teas such as Pu’er tea and Chin-brick tea.TBs are a class of water-soluble brown polymers with multi-molecular weight distribution produced by the oxidative polymerisation of tea polyphenols during the fermentation process of dark tea,both enzymatically and non-enzymatically.TBs have been extracted and purified from dark tea all the time,but the obtained TBs contain heterogeneous components such as polysaccharides and caffeine in the bound state,which are difficult to remove.The isolation and purification process was tedious and required the use of organic solvents,which made it difficult to industrialise TBs.In this study,epigallocatechin(EGC),epigallocatechin gallate(EGCG),epigallocatechin gallate(ECG),EGC/EGCG(mass ratio 1:1),EGCG/ECG(mass ratio 1:1),EGC/ECG(mass ratio 1:1)and EGC/EGCG/ECG(mass ratio 1:1:1)as substrates and catalyzed by polyphenol oxidase(PPO)and peroxidase(POD)in turn to produce TBs,named TBs-dE-1,TBs-dE-2,TBs-dE-3,TBs-dE-4,TBs-dE-5,TBs-dE-6 and TBs-dE-7.The physicochemical properties and the antibacterial activity and mechanism of TBs-dE-1–7 were investigated.Sensory and colour difference measurements showed that all seven tea browning samples showed varying degrees of brownish hue.Zeta potential in aqueous solutions at pH 3.0–9.0 indicated that TBs-dE-1–7 was negatively charged and the potential increased with increasing pH.The characteristic absorption peaks of TBs-dE-1–7 were observed at 208 and 274 nm by UV-visible(UV-vis)scanning spectroscopy.Fourier transform infrared(FT-IR)spectra indicated that they were phenolic compounds.TBs-dE-1–7 showed significant inhibition of Escherichia coli DH5α(E.coli DH5α).TBs-dE-3 showed the strongest inhibitory effect with minimum inhibitory concentration(MIC)of 1.25 mg mL–1 and MBC of 10 mg mL–1,followed by TBs-dE-5 and TBs-dE-6.These three TBs-dEs were selected to further investigate their inhibition mechanism.The TBs-dE was found to damage the extracellular membrane of E.coli DH5α,causing leakage of contents,and increase intracellular reactive oxygen content,resulting in abnormal cell metabolism due to oxidative stress.The results of the study provide a theoretical basis for the industrial preparation and product development of TBs.

Antibacterial mechanism of Cu-bearing 430 ferritic stainless steel

Copper(Cu)-bearing stainless steel has testified its effectiveness to reduce the risk of bacterial infections.However,its antibacterial mechanism is still controversial.Therefore,three 430 ferritic stainless steels with different Cu contents are selected to conduct deeper research by the way of bacterial inactivation from two aspects of material and biology.Hereinto,electrochemical and antibacterial results show that the increase in Cu content simultaneously improves the corrosion resistance and antibacterial property of 430 stainless steel.In addition,it is found that Escherichia coli(E.coli)on the surface 430 Cu-bearing stainless steel by the dry method of inoculation possesses a rapid inactivation ability.X-ray photoelectron spectroscopy(XPS)aids with ion chelation experiments prove that Cu(Ⅰ)plays a more crucial role in the contact-killing efficiency than Cu(Ⅱ),resulting from more production of reactive oxygen species(ROS).

Antibacterial mechanism of Ginkgo biloba leaf extract when applied to Shewanella putrefaciens and Saprophytic staphylococcus

The antimicrobial mechanism of Ginkgo biloba leaf extracts(GBLE)when applied to predominant spoilage bacteria(Shewanella putrefaciens and Saprophytic staphylococcus)on refrigerated pomfret and minimal inhibitory concentrations(MICs)were measured by the plate counting method.GBLE at MIC and 2MIC were prepared in tryptic soy broth(TSB)medium and equivalent amounts of sterile distilled water were used in place of GBLE as a control group.The impact of GBLE on the growth of bacteria,the permeability of cell membrane,and cell wall were also investigated by growth curve of bacteria,alkaline phosphates activity(AKP),and electrical conductivity.A scanning electron microscope(SEM)was used to study the effects of GBLE on the cellular structure of S.putrefaciens and S.staphylococcus.The results showed that the MICs of GBLE when applied to S.putrefaciens and S.staphylococcus were 100 mg/mL,the inhibitory rates of MIC and 2MIC concentrations of GBLE when applied to S.putrefaciens were 36.11%and 100%,while 27.78%and 62.22%for S.staphylococcus.Meanwhile,GBLE inhibited the growth of S.putrefaciens and S.staphylococcus until the number of cells at 2MIC values decreased to 0 and 4.29 log CFU/mL,respectively,after 24 h.The electrical conductivity of bacteria increased with GBLE treatment,which was followed by an increased leakage of AKP.The SEM revealed that the structure of bacterial cells was destroyed and the bacteria began to be adhere to each other.The inhibition effect of GBLE when applied to S.putrefaciens and S.staphylococcus was related to the damage of cell membrane and cell wall.It was also revealed that GBLE damages the morphology of bacteria and had stronger effects on the cell membrane of S.putrefaciens than that of S.staphylococcus.

Linalool against Hafnia alvei,its antibacterial mechanism revealed by metabolomic analyses

Linalool,a major component of aromatic plant essential oils,has an antibacterial effect against Hafnia alvei,which can induce food spoilage.In this study,we aimed to investigate the antibacterial effect and mechanism of linalool against H.alvei.Linalool treatment resulted in excessive reactive oxygen species(ROS)accumulation,which resulted in destruction of the cell membrane.According to the field emission scanning electron microscopy(FESEM)and flow cytometry(FCM)results,it was confirmed that the membrane structure of H.alvei was destroyed.Moreover,metabolomics analysis showed that there were 64 and 73 differentially expressed metabolites screened by mass spectrometry in positive and negative ion modes,respectively,suggesting that nucleic acid metabolism,the respiratory chain and energy metabolism were negatively affected by linalool.Biochemical validation confirmed that the activities of malate dehydrogenase(MDH),and succinate dehydrogenase(SDH)and respiratory metabolism were reduced after linalool treatment.It was therefore concluded that the cell membrane was damaged,nucleic acid metabolism was disturbed,and energy metabolism was reduced by inhibition of the respiratory chain and tricarboxylic acid(TCA)cycle.These results revealed the antibacterial mechanism of linalool against H.alvei,and support the use of linalool as a potential natural preservative to control H.alvei.

Breaking or following the membrane-targeting mechanism:Exploring the antibacterial mechanism of host defense peptide mimicking poly(2-oxazoline)s

Peptides exert important biological functions but their application is hindered by their susceptibility to proteolysis and poor stability in vivo.Thus,functional peptide mimics have drawn a great deal of attention to address this challenge.Poly(2-oxazoline)s,a class of biocompatible and proteolysis-resistant polymer,can work as host defense peptide mimics without following the general membrane-targeting mechanism as shown in our previous work.This observation encouraged us to figure out if poly(2-oxazoline)s are special and break the general membrane-targeting mechanism of host defense peptides and their mimics.In this study,we aimed at the connection between structure and antibacterial mechanism of poly(2-oxazoline)s.A new γ-aminobutyric acid(GABA)-pendent poly(2-oxazoline)was synthesized and investigated to compare with glycine-pendent poly(2-oxazoline)in our previous study,with the former polymer has two extra CH2 groups in the sidechain to increase the hydrophobicity and amphiphilicity.Membrane depolarization assay suggested that incorporating two more CH2 groups into the sidechain of poly(2-oxazoline)resulted in a mechanism switch from DNA-targeting to membrane-targeting,which was supported by the slow time-kill kinetics and slightly distorted and sunken membrane morphology.Besides,GABA-pendent poly(2-oxazoline)showed potent activity against methicillin-resistant S.aureus and low hemolysis on human red blood cells.Moreover,repeated use of the antimicrobial poly(2-oxazoline)did not stimulate bacteria to obtain resistance,which was an obvious advantage of membrane-targeting antimicrobial agents.

Kinetically regulated one-pot synthesis of cationic gold nanoparticles and their size-dependent antibacterial mechanism

Cationic gold nanoparticles(cAuNPs)have been regarded as promising candidates for antibacterial applications due to their high surface charge density,favorable biocompatibility,and controllable surface chemistry.Nevertheless,the complicated fabrication process and unclear antibacterial mechanism have greatly hindered the further biomedical application of cAuNPs.Herein,we have developed a simple and controllable strategy for synthesizing cAuNPs with tailored size and antibacterial behavior by kinetically modulating the reaction process.Specifically,a functional ligand,(11-mercaptoundecyl)-N,N,Ntrimethylammonium bromide(MUTAB),was chosen to chemically manipulate the positive surface charge of cAuNPs via a one-step strategy.The size of cAuNPs could be flexibly adjusted from 1.1 to 14.8 nm by simply elevating the stirring speed of the reaction from 0 to 1500 rpm.Further studies revealed that the antibacterial effect of cAuNPs was strongly correlated with the particle size.MUTAB-protected ultrasmall gold nanoclusters(MUTAB-AuNCs)were able to eradicate E.coli at a concentration as low as 1.25μg mL^(-1),while the minimum inhibitory concentration of MUTAB-AuNPs with a large size for E.coli was 5μg mL^(-1).Mechanistic investigation revealed that MUTAB-AuNPs were able to damage the bacterial membrane and stimulate the production of reactive oxygen species more effectively than MUTAB-AuNCs.Conversely,MUTAB-AuNCs were more active in inducing membrane depolarization in contrast to MUTAB-AuNPs,suggesting the unique size-dependent antibacterial manner of cAuNPs.This study presents a new strategy for the controlled preparation of cAuNPs with distinct sizes and antibacterial behavior,laying a valuable foundation for developing efficient cationic NP-based bactericidal agents.

Antibacterial Activity and Mechanism of ZnO/Cu^(2+)-Chitosan/Montmorillonite

A new composite antibacterial material ZnO/Cu^(2+)-Chitosan/Montmorillonite (ZCCM) was prepared with montmorillonite as carrier,Zn(Ac)_(2)·2H_(2)O,Cu(NO_(3))_(2)·3H_(2)O and chitosan as raw materials.ZCCM was characterized by X-ray diffraction,nitrogen physical adsorption,scanning electron microscopy and energy dispersion spectrometry.The antibacterial activity of ZCCM against Escherichia coli,Salmonella typhimurium,and Staphylococcus aureus was evaluated by minimal inhibitory concentration,minimum bactericidal concentration and the influence of growth curves.ZCCM displays excellent antibacterial activity which is higher than ZnO-Montmorillonite,Cu^(2+)-Montmorillonite and ZnO/Cu^(2+)-Montmorillonite.In addition,the antibacterial mechanism of ZCCM was investigated by analyzing bacterial morphology,integrity of cell membrane,lipid peroxidation and the effect of histidine on antibacterial activity of materials.It is found that cell morphologies of bacteria are damaged and bacterial cells are shrunken.With the increase of cell membrane permeability,the intracellular dissolved matters leak continuously.What’s more,the reactive oxygen species are generated and biomacromolecules are oxidized.

An antibacterial mechanism of titanium alloy based on micro-area potential difference induced reactive oxygen species

Antimicrobial material is highly desired because of the increasing demand in biomedical application to prevent from the formation of biofilm.A common strategy for enhancing the antibacterial property of a metal material is to incorporate toxic metal such as Cu and Ag.However,the reported Cu^(2+)or Ag~+released concentration from antibacterial alloys was much less than the reported minimum inhibitory ion concentrations(MIC),revealing the existence of an unknown alternative antimicrobial mechanism not relying on the toxicity of the metal ions.Herein,we proposed a new antibacterial mechanism that the antibacterial effectiveness of the different alloys is proportional to the micro-area potential differences(MAPDs)on the surface of the alloys.We designed three kinds of Ti-M(M=Zr,Ta and Au)alloys to eliminate the potential antibacterial contribution from Cu and Ag ion.We demonstrated that high MAPDs are associated with great production of reactive oxygen species(ROS),resulting in the killing effect to the biofilm known to be associated with implant infections(Staphlococcus aureus and Escherichia coli).These results provide new insights for the design of antibacterial alloys.

Study on antibacterial mechanism of electron beam radiation on Aspergillus flavus

Contamination with Aspergillus flavus,which produces carcinogenic metabolites,during the post-harvest storage of agricultural products seriously endangers human health and safety.In this study,the efficacy of short-term electron beam irradiation processing with high sterilization efficiency,no contamination and no additives was evaluated for the prevention and control of A.flavus.The effects of irradiation on Aspergillus growth were determined based on analyses of physical and chemical indexes,morphology,mycelial growth,spore germination rates,mycelial dry weights,and toxin-producing ability.The effects of irradiation on the cell membrane and cell wall of A.flavus were investigated based on assays of the chitin content,chitinase activity,protein concentration,and malondialdehyde content.Damage to the antioxidant system was determined by the hydrogen peroxide content,catalase activity,superoxide dismutase activity,superoxide anion radical scavenging activity and rates of 1,1-diphenyl-2-trinitrophenylhydrazine inhibition.The inhibitory effect of irradiation on peanut invasion by A.flavus was verified.After irradiation,the thallus morphology was destroyed,mycelial growth was inhibited,and the spore germination rate,mycelial dry weight,and toxin-producing ability of A.flavus were reduced.Chitinase activity and the malondialdehyde content increased,while the chitin and total protein contents decreased.Catalase activity,superoxide dismutase activity,superoxide anion radical scavenging activity,and the rate of 1,1-diphenyl-2-trinitrophenylhydrazine inhibition decreased,while the hydrogen peroxide content increased after irradiation.These findings suggested that electron beam irradiation can effectively inhibit the normal growth and toxin production of A.flavus.Irradiation increased cell membrane permeability and decreased the integrity of the cell wall.The antioxidant system was damaged to some extent.Compared with that in unirradiated A.flavus,high-dose electron beam irradiation effectively inhibited growth.As a means of postharvest control,electron beam irradiation may have wide applications in the agricultural industry.

Action Mechanism of Antibacterial Hydrolysate from Ruditapes philippinarum

[Objectives] The antibacterial mechanism of protein hydrolysate from Ruditapes philippinarum（ named RPPH） was studied in this article. [Methods]The integrity of bacteria＇s wall and membrane was determined by some traditional ways. [Results]The growth of Staphylococcus aureus and Bacillus subtilis were inhibited by RPPH in the logarithmic phase. The activity of alkaline phosphatase could be detected in the culture solution. The results showed that the protein content and the conductivity of two kinds of bacteria increased with the extension of incubation time. The results of scanning electron microscope revealed that it emerged the phenomenon of agglomeration with the extension of response time in the culture solution of S. aureus,and the cell shape became irregular,a large number of cells stuck together,afterwards intracellular material was released from bacteria,and the boundaries among cells completely disappeared. The cell surface of B. subtilis became rough,the cells began to adhere,intercellular boundaries became blurred,subsequently cells broke,and then intracellular material leaked out after treating for 9 h. The form of B. subtilis could be roughly identified from the remnants of the bacterial debris,and most of the bacteria had been completely cracked and died. Transmission electron microscope results showed that the surface of S. aureus became rough,with uneven distribution of cytoplasm,and darker substances appeared in the middle,followed by leakage of large numbers of intracellular material. Massive cells became dead when treating for 9 h. B. subtilis cells began to shrink,and cytoplasm was distributed unevenly. The significant phenomenon of plasmolysis and rupture of cell wall could be observed. Afterwards,intracellular material spilled out,only the residual and ambiguity nucleoplasm area could be seen,and cells were killed. [Conclusions] Therefore,it was speculated that the RPPH could destroy cell wall and membrane of the two kinds of bacteria,change the permeability of cells membrane,result in the leakage of intracellular substances and enter within the bacterial cells to affect their normal physiological metabolism which led to death.

Recent Advancements on Photothermal Conversion and Antibacterial Applications over MXenes-Based Materials

The pernicious bacterial proliferation and emergence of super-resistant bacteria have already posed a great threat to public health,which drives researchers to develop antibiotic-free strategies to eradicate these fierce microbes.Although enormous achievements have already been achieved,it remains an arduous challenge to realize efficient sterilization to cut off the drug resistance generation.Recently,photothermal therapy(PTT)has emerged as a promising solution to efficiently damage the integrity of pathogenic bacteria based on hyperthermia beyond their tolerance.Until now,numerous photothermal agents have been studied for antimicrobial PTT.Among them,MXenes(a type of two-dimensional transition metal carbides or nitrides)are extensively investigated as one of the most promising candidates due to their high aspect ratio,atomic-thin thickness,excellent photothermal performance,low cytotoxicity,and ultrahigh dispersibility in aqueous systems.Besides,the enormous application scenarios using their antibacterial properties can be tailored via elaborated designs of MXenes-based materials.In this review,the synthetic approaches and textural properties of MXenes have been systematically presented first,and then the photothermal properties and sterilization mechanisms using MXenes-based materials are documented.Subsequently,recent progress in diverse fields making use of the photothermal and antibacterial performances of MXenes-based materials are well summarized to reveal the potential applications of these materials for various purposes,including in vitro and in vivo sterilization,solar water evaporation and purification,and flexible antibacterial fabrics.Last but not least,the current challenges and future perspectives are discussed to provide theoretical guidance for the fabrication of efficient antimicrobial systems using MXenes.

Silver Supported on White Carbon Black Containing Rare Earths as Antibacterial Material

The antimicrobial effect of the Ag-White Carbon Black containing rare earth was investigated. Inorganic antibiotic materials consist of the antibacterial ion, the additive and the carrier. The sol-gel method was used to prepare the white carbon black carrier. Ag+ was selected to be the antibacterial ion, and cerous nitrate was selected to be the additive. They were synthesized on the white carbon black carrier. The structures and properties of antibacterial material were characterized by inductively coupled plasma, particle size measurement instrument, fourier transform infrared and enumeration tests (Escherichia coli as experimental bacterium). Results showed that the amount of antibacterial ions and bacteriostasis rate of this new material are higher than those for the general Ag-antibacterial white carbon black (without containing rare earth). Ag+ was bound to white carbon black by ion exchange process and adsorption process. Bacteriostasis rate is over 99%, and the particle size can be extended down to 7 μm with a narrow size distribution. Other advantages of this material are good thermal and light stability. Furthermore, from the antibacterial experiment in rubber and the coating surface of metal, this new material showed promising results. The possible antibacterial mechanism was also proposed through all the experimental data in this study.

Preparation and Characterization of Cu-Ag-inorganic Antibacterial Material Containing Rare Earths

Inorganic antibacterial materials consist of the antibacterial ions, the additives and the carrier. In this study, we synthesized a new inorganic antibacterialmaterial, of which Cu2+ and Ag+ were selected to be the bi-component antibacterial ions, cerous nitrate served as the additives, and the white carbon black was chosen as the carrier, which was prepared by a sol-gel method. The as-synthesized antibacterial material was characterized by inductively coupled plasma, particle size measurement instrument, scanning electron microscope and enumeration tests. The result showed that the amount of antibacterial ions and bacteriostasis rate of this new material are higher than those for the single-ion inorganic antibacterial material. In addition, the particle size of this material can be extended down to 7 μm with a narrow size distribution. Other advantages of this material are its loose and dispersive structure, good thermal and light stability. From the antibacterial experiment in rubber and the coating surface of metal, this new material showed promising results. The possible antibacterial mechanism was also proposed through all the experimental data in this study.

Evaluation of the antibacterial mechanism and biofilm removal effect of eugenol on Vibrio vulnificus and its application in fresh oysters

Eugenol is a natural active substance with high antibacterial activity,but its antibacterial activity against Vibrio vulnificus has not been extensively studied.The purpose of this study was to investigate the antibacterial and biofilm-clearing abilities and potential mechanisms of eugenol against V.vulnificus,and to provide knowledge for the use of eugenol to prevent oyster contamination.It was found that eugenol had an encouraging antibacterial effect on V.vulnificus with a minimum inhibitory concentration(MIC)of 0.2 mg/mL.The accumulation of reactive oxygen species(ROS)and the increase of malondialdehyde(MDA)content suggest that oxidative stress is involved in the bactericidal mechanism.Moreover,cell membrane hyperpolarization,changes in cell membrane integrity and morphology suggest that eugenol can reduce the permeability and integrity of cell membranes in V.vulnificus.In addition,eugenol produced a significant biofilm clearance effect on V.vulnificus,as evidenced by the reduced amount of biofilm and the reduction of polysaccharides and viable cells in the biofilm.Finally,eugenol was able to effectively inhibit the activity of V.vulnificus in artificially contaminated oyster at 4°C and 25°C.But sensory analysis showed that 0.10%eugenol was most acceptable to trained panelists.All of these highlight the great promise of eugenol as a natural bacteriostatic agent for the food industry.

A broad-spectrum novel bacteriocin produced by Lactobacillus sakei in Nanjing Steamed Roast Duck:Purification,antimicrobial characteristics,and antibacterial mechanisms

A new bacteriocin(Y19-2)was isolated,purified,and characterized from Nanjing Steamed Roast Duck,a traditional Chinese fermented meat product.Purification was performed via ammonium sulfate fractional precipitation,diethyl aminoethyl(DEAE)-52 cellulose ion-exchange chromatography,Sephadex G-50 chromatography,and reversed-phase high-performance liquid chromatography(RP-HPLC).SDS-PAGE analysis showed the molecular weight of Y19-2 is 20 kDa,making it fall into the third type of bacteriocin based on the classifications of bacteriocins according to their molecular weights.In addition,Y19-2 is heat-resistant as suggested by a merely 14%loss of its antibacterial activity when heated at 121°C for 30 min.In acidic conditions(pH 3–5),Y19-2 has obvious antibacterial activity against both gram-positive and gram-negative bacteria,and such an activity can be partially inactivated by pepsin and trypsin while being completely inhibited by papain.Scanning electron microscopy and differential thermal scanning analysis showed that Y19-2 could inhibit bacteria growth by destroying the bacterial cell wall and affecting the synthesis of bacteria's nucleic acids.Therefore,Y19-2 is potential as a bioprotective agent in foods.

Developing high photocatalytic antibacterial Zn electrodeposited coatings through Schottky junction with Fe3+-doped alkalized g-C_(3)N_(4) photocatalysts

Pure Zn coatings easily lose their protective performance after biofouling because they have no antibacterial effect under visible light.In this study,we fabricate a new antibacterial Zn composite coating using electrodeposition to couple Fe3+-doped alkalized g-C_(3)N_(4)(AKCN-Fe)into an existing Zn coating and show that the AKCN-Fe enhances antibacterial property of the Zn coating under visible light.We attribute this enhancement to the high photocatalytic performance,high loading content,and good dispersion of AKCN-Fe.In addition,the photocatalytic antibacterial mechanism of the composite coating is supported by scavenger experiments and electron paramagnetic resonance(EPR)measurements,suggesting that superoxide(·O_(2)^(-))and hydroxyl radical(·OH)play main and secondary roles,respectively.