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Escherichia coli O157:H7 ( E. coli O157:H7) is one of the most common pathogens in fresh vegetables and fruits, and most of the diseases produced by E. coli O157:H7 are associated with biofilms. Cold nitrogen plasma (CNP) is a cold sterilization technique which has no residue. However to completely eliminate the biofilm on the surface of vegetables the processing power and time of CNP have to be enhanced, which will impact on the quality of fruits and vegetables. Thus the sequential treatment of CNP and phage techniques was engineered in this study. Compared to treatment performed separately, sequential treatment not only had more mild treatment conditions as 400 W CNP treatment for 2 min and 5% phage treatment for 30 min, but also exhibited more remarkable effect on eradicating E. coli O157:H7 biofilms in vitro and on vegetables. The population of E. coli O157:H7 was approximately reduced by 2 log CFU/cm 2 after individual treatment of 5% phages for 30 min or 500 W CNP for 3 min. While the sequential treatment of CNP (400 W, 2 min) and phages (5%, 30 min) reduced the E. coli O157:H7 viable count in biofilm by 5.71 log CFU/cm 2 . Therefore, the sequential treatment holds a great promise to improve the current treatment systems of bacterial contamination on different vegetable surfaces. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the antibacterial activity of clove oil-loaded chitosan nanoparticles (CO@CNPs) and gelatin electrospun nanofibers against Escherichia coli O157:H7 ( E . coli O157:H7) biofilms on cucumbers. The optimal CO@CNPs were prepared when the initial concentration of clove oil (CO) was 2.5 mg/mL according to the ionic crosslinking method. CO@CNPs showed high antibacterial activity against E . coli O157:H7 biofilms. After 8 h treatment, almost 99.98% reduction in E . coli O157:H7 population was achie v ed when CO@CNPs were applied at 30% (w/v). Subsequently, the prepared CO@CNPs were incorporated successfully within gelatin nanofibers by electrospinning. After 9 mg/mL gelatin/CO@CNPs treatment for 24 h, the population of E . coli O157:H7 biofilm reduced by about 99.99% in vitro . Further, the application of gelatin/CO@CNPs nanofibers on cucumber against E . coli O157:H7 biofilm was evaluated as well. After 6 mg/mL and 9 mg/mL gelatin/CO@CNPs nanofibers treatment at 12 °C for 4 days, 4.28 and 4.97 log 10 reductions of E . coli O157:H7 biofilm in population were observed, respectively. Finally, the sensory evaluation results implied that the gelatin/CO@CNPs nanofibers treatment could maintain the color and flavor of cucumber well for > 4 days. [ABSTRACT FROM AUTHOR]

This work describes the effect of cold nitrogen plasma to enhance the antibacterial activity of poly(ethylene oxide) (PEO) nanofibers containing antibacterial agent. Beta-cyclodextrin (β-CD) and tea tree oil (TTO) were used as a host-guest to form water-soluble inclusion complex. The encapsulation efficiency of TTO in inclusion complex could reach 73.23% at 60 °C. As antibacterial agent, the inclusion complex was encapsulated into PEO matrix by electrospun. After plasma treatment, the release efficiency of antibacterial agent from PEO nanofibers was improved. As a result, the antibacterial activity of PEO nanofibers was enhanced accordingly. The plasma-treated nanofiber membranes achieved the highest antibacterial activity against Escherichia coli O157:H7, which was tested on the beef for 7 d, with inhibition efficiently of 99.99% whether at 4 °C or 12 °C. The plasma-treated PEO nanofiber membranes containing TTO/β-CD inclusion complex (TTO/β-CD-IC) can prolong the shelf-life of beef, suggesting it has potential application in active food packaging. [ABSTRACT FROM AUTHOR]

In recent years, phages used for the reduction of pathogenic bacteria have fostered many attentions, but they are liable to lost bioactivity in food due to the presence of acidic compounds, enzymes and evaporite materials. To improve the stability of phages, a chitosan edible film containing liposome-encapsulated phage was engineered in the present study. The characteristics of liposome-encapsulated phage and the chitosan film containing liposome-encapsulated phage were investigated. The encapsulation efficiency of phages in liposome reached 57.66 ± 0.12%. Besides, the desirable physical properties of chitosan film were obtained. The chitosan film embedded with liposome-encapsulated phage exhibited high antibacterial activity against Escherichia coli O157:H7, without the impact on the sensory properties of beef. Hence, chitosan film containing liposome-encapsulated phage could be a promising antibacterial packaging for beef preservation. [ABSTRACT FROM AUTHOR]

Guided by the principle of hurdle technology, a high-efficiency antibacterial agent (AA) had been formulated, which contained six kinds of essential oils, three pieces of food additives and ethyl alcohol. The antibacterial effects of AA against E. coli O157:H7 biofilm on simulated and real cucumbers were testified by MTT staining method, colony-forming unit (CFU) counting method, scanning electron microscopy (SEM) analysis and confocal laser scanning microscopy (CLSM) assay. The remarkable anti-biofilm activity of AA was achieved under low concentration and short treatment duration. The results also revealed that AA inhibited the multiplication of E. coli O157:H7 via destroying the cell membrane integrity. Besides, color, texture and sensory evaluation illustrated that AA could be applied as a disinfectant to eliminate the biofilm formed on cucumber without impact on food quality. Practical Applications As a kind of high-efficiency antimicrobials, AA has significant inhibition and elimination effects on biofilm under a low concentration and short incubation time. Especially, AA was effective to eliminate the formed E. coli O157:H7 biofilm on the surface of cucumber without impact on the quality and flavor of the product. On the basis of the results, we believe that AA can be applied in vegetables or fruits processing and preservation. [ABSTRACT FROM AUTHOR]

As a natural antibacterial agent, Artemisia annua oil ( AAO) exhibited significant antibacterial effect on Escherichia coli O157:H7. However, AAO was volatile and not suitable for surface coatings of fresh produce. Therefore, the edible agar films containing chitosan and AAO liposomes were engineered to overcome the defect. Chitosan was added in the film to enhance the antibacterial activity. Finally, the results showed the mean size of AAO liposomes was about 191.8 nm with a polydispersity index ( PDI) of 0.463. The absolute zeta potential value was greater than 30 mV, and the loading efficiency ( LE) of 5.0 mg mL−1 AAO liposome was 67.45%. As a proof of concept, the antibacterial activity of the films against E. coli O157:H7 on cherry tomatoes was evaluated. The results indicated that the incorporation of AAO liposomes as a natural antibacterial agent possessed bacteriostatic effect, which had potential for using the developed film as an active packaging. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the antimicrobial effects of cold nitrogen plasma (CNP) and clove oil against Escherichia coli O157:H7 ( E. coli O157:H7) biofilm on lettuce. Both clove oil (1 mg/mL, 2 mg/mL and 4 mg/mL) and CNP (400–600 W) displayed significant eradication effect on E. coli O157:H7 biofilms in vitro ( p < 0.001). Subsequently, the antibiofilm effect of combined treatment was studied as well. Compared with the respective treatment, combined treatment exhibited remarkable synergistic effect on eradicating E. coli O157:H7 biofilms. The confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) had also visually testified that the antibacterial effects of clove oil on E. coli O157:H7 biofilms (in vitro and on lettuce) were enhanced by CNP at 400 W for short treatment duration. The results of sensory evaluation indicated that combined treatment has mild negative effect on lettuce quality. Moreover, the synergetic antibacterial mechanism of clove oil and CNP against E. coli O157:H7 was concluded as that they could damage the bacterial cell wall and the outer membrane, leading to leakage of cellular components, such as nucleic acid and ATP. [ABSTRACT FROM AUTHOR]

Escherichia coli O157:H7 (E. coli O157) is still one of the main pathogenic strains causing food poisoning. Here in, we established a strategy that can simultaneously remove free E. coli O157 and the biofilms it forms. Composite nanofiber (fP-NF) films were synthesized successfully by co-encapsulating E. coli O157 phages which isolated from domestic sewage and D -phenylalanine (D-Phe) into sodium alginate (SA)/polyethylene oxide (PEO) nanofibers by electrospinning. And dehydrated trehalose was added as a phage protectant. When SA:PEO is 3:9, the spinning solution has the optimum conductivity and viscosity, the average diameter of the obtained fP-NFs is 421.87 nm, and the mechanical strength and transparency of the fP-NF film are the best. The thermal stability of the fP-NF film was good, and the phage activity in the fiber was well preserved. The remaining population of phages in fP-NF membranes was still close to 106 PFU/mL after one week of placement, and the cumulative release efficiencies of phages at both room temperature (25 °C) and refrigerated storage temperature (4 °C) were above 70%. The antibacterial experiment showed that compared with the control group, the addition of D-Phe slightly enhanced the antibacterial activity of the nanofiber films against free E. coli O157, and the bactericidal rate within 8 h was 99.74%. On the other hand, D-Phe significantly enhanced the inhibitory activity of the nanofiber films against E. coli O157 biofilms, with the inhibition rate exceeding 99.99% within 72 h. The application results further confirmed that the addition of D-Phe could significantly enhance the inhibitory activity of nanofiber films on E. coli O157 proliferation and biofilm formation during short-term storage of beef and fruits and vegetables. It provides an important strategy and reference for the development of new active food packaging materials. • A new nanofiber film that efficiently eliminates E. coli O157 biofilms was assembled. • The addition of D-Phe enhanced the inhibition effect of the nanofibers on biofilms. • Nanofiber film efficiently reduced the risk of foods contamination with E. coli O157. [ABSTRACT FROM AUTHOR]

• Phlorotannin (PT) and Momordica charantia polysaccharides (MCP) showed antibacterial and antioxidative activities. • MCP was used as the matrix of nanofibers to encapsulate phlorotannin. • The release efficiency of PT from nanofibers was improved by cold plasma treatment. Momordica charantia polysaccharide (MCP) has been repeatedly reported due to its anti-diabetic properties. Up to our knowledge, no research has discussed the use of MCP as a nanofiber matrix in an active food packaging. As an antibacterial and anti-oxidant agent, phlorotannin (PT) was encapsulated in MCP nanofibers to promote these activities. Nanofiber membranes were treated with cold plasma to increase their application performance. Antioxidant and antibacterial activities of PT and MCP against Escherichia coli O157:H7 were individually evaluated. The prepared nanofibers were assessed for their physical and mechanical properties in order to select the better-characterized ones. The successfulness of PT loading into MCP nanofibers was confirmed using SEM, AFM, TGA and DSC. After cold plasma treatment, the release efficiency of PT from the nanofibers was enhanced by 23.5 % (4 °C) and 25 % (25 °C), respectively. Correspondingly, both antibacterial and anti-oxidant activities of PT/MCP nanofibers were markedly improved. [ABSTRACT FROM AUTHOR]

Escherichia coli O157:H7 (E. coli O157:H7) easily forms biofilms on pores and veins of plant, which poses a serious hazard to safety of ready-to-eat vegetables. Therefore, this study was designed to evaluate inhibition mechanism of clove oil on E. coli O157:H7 biofilm and apply it to vegetable for reduce risk of contamination. The results of crystal violet staining showed that clove oil could effectively remove biofilm. After treatment of biofilm with clove oil (2 MBIC), the results of resazurin method showed that bacterial metabolic activity decreased by 61.48%, and results of phenol-sulfuric acid method and Coomassie brilliant blue method showed that extracellular protein and polysaccharide content decreased by 62.76% and 47.5%, respectively. This indicates that clove oil can affect biofilm through above aspects. Finally, solid liposomes (SLPs) were prepared and applied to vegetables, which was first time that SLPs were used to remove biofilms. The results showed that clove oil SLPs exhibited excellent anti-biofilm activity at 4 °C and 25 °C without affecting senses and quality of vegetables. Therefore, the clove oil SLPs can exert a long-lasting antibacterial effect, effectively removing E. coli O157:H7 biofilm on vegetable surface, and prolonging the shelf life. • Clove oil can inhibit the synthesis of extracellular polysaccharides in biofilm. • Clove oil can destroy the biofilm barrier and cause the loss of bacterial metabolic activity. • The clove oil SLPs can maintain good stability after 15 d of storage. • The long-lasting release of Clove oil from SLPs was achieved. • Clove oil SLPs can remove E. coli O157:H7 biofilm on the surface of vegetables. [ABSTRACT FROM AUTHOR]

The efficacy of bacteriophages as antibacterial agents has fostered the approval and commercialization of several products intended to reduce the risk of food corruption by bacterium. This study investigated the antibacterial activity and mechanism of bacteriophages against Escherichia coli O157:H7. Around 3.75 log cfu/mL reductions in E. coli O157:H7 populations were observed after 109 PFU/mL bacteriophages treatment for 12 hr. Subsequently, bacteriophages were incorporated into a liposome system to improve its chemical stability. Then, poly‐L‐lysine (PLL) was used to further enhance the stability of bacteriophages liposomes. The optimal PLL‐coated bacteriophage liposomes encapsulated 0.2 × 1011 PFU/mL bacteriophages, with polydispersity index (PDI) of 0.268, zeta potential of 21.8 mV, and encapsulation efficiency of 57.59%. In addition, long‐term antibacterial activity illustrated bacteriophages encapsulated in PLL‐coated liposome could extend the treatment time, achieving 2.44 log cfu/mL reductions in E. coli O157:H7 population after 1 day incubation in pork suspension. Practical applications: The prepared poly‐L‐lysine‐coated bacteriophage liposomes exhibited a promising prospect for biocontrol of Escherichia coli O157:H7 in pork and their further products, without significant impacts on the quality of pork products. The results obtained in this study may provide theoretical basis for meats preservation and broaden the antimicrobial application of bacteriophage in food industries. [ABSTRACT FROM AUTHOR]

Recently, natural essential oils have been extensively studied for anti-bacterial application in foods due to their safety and high biological activity. Herein, Litsea cubeba essential oil (LC-EO) was applied as a natural anti-bacterial agent for exploring its anti-bacterial mechanism against Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157:H7). The LC-EO could effectively inhibit the growth of EHEC O157:H7 and the minimal inhibitory concentration (MIC) was 0.5 mg/mL. In the study of anti-bacterial mechanism, the LC-EO was proved with good membrane penetration ability, which could destroy bacterial cell structure and disorder membrane permeability, thereby causing the leakage of intracellular organic matters. Furthermore, the inhibitory effects of LC-EO on physiological metabolism of EHEC O157:H7, including respiratory metabolism, enzyme activity, the replication of nucleic acid and the transcription level of main virulence genes (stx1 , stx2 , ehxA , eae), were also demonstrated in this study. Specially, the possible action mechanism of different components of LC-EO on bacterial genetic material was revealed deeply on molecular level by the molecular docking technology. Finally, the results of application evaluation indicated that the addition of LC-EO at MIC in different vegetable juices could maintain anti-bacterial rate above 99.9% for 4 days without remarkable influence on foods sensory quality. The information in this study provides the necessary theoretical foundation for extending the application of LC-EO in food preservation. • Litsea cubeba essential oil can break bacterial membrane structure. • Litsea cubeba essential oil can inhibit bacterial respiratory metabolism. • Litsea cubeba essential oil can impede bacterial nucleic acid replication. • Litsea cubeba essential oil can inhibit the transcription level of virulence genes. • Litsea cubeba essential oil has good application effect in vegetable juices. [ABSTRACT FROM AUTHOR]

As a non-thermal sterilization method, pulsed light (PL) has been widely applied in food industries to control the microbial contamination, however little is known about the antimicrobial mechanism of PL. This study deeply investigated the antimicrobial mechanism of PL against Escherichia coli O157:H7 (E. coli O157:H7). The changes of morphology, endoenzyme, entocyte, respiratory metabolism and DNA of E. coli O157:H7 after PL treatment were emphatically studied. TEM and SEM results exhibited that cell integrity was destroyed heavily after PL treatment. Entocyte including proteins, ATP and DNA were reduced remarkably for PL-treated samples. In addition, the activity of ATPase, β-galactosidase, alkaline phosphatase, topoisomerase, as well as the metabolism were inhibited for E. coli O157:H7 with PL treatment. The electron spin resonance spectrum validated the production of hydroxyl radical by PL, thus resulting in the elevation of intracellular reactive oxygen and the acceleration of cell death. Finally, PL displayed better antibacterial activity in carrot juice without adverse effect on its quality. • The antimicrobial mechanism of pulsed light (PL) was deeply explored. • PL can impact the morphology, enzyme, entocyte and metabolism of bacteria. • The generation of hydroxyl radical by PL can accelerate the death of bacteria. [ABSTRACT FROM AUTHOR]

Pulsed magnetic fields (PMF) as a non-thermal sterilization has broad application prospects, but at this stage its bactericidal effect is not satisfactory. The essential oils have been proved with good antimicrobial effects. However, they will cover the original flavor of the food products at high dosages. In order to overcome the defects of PMF and essential oils, the bactericidal effects of pulsed magnetic fields in combination wdrith Litseacubeba essential oil (LC-EO) treatments were assessed in cucumber, carrot, spinach and bitter gourd juices. The optimal synergistic effects were found using PMF (3 times under 8T, 60 pulses) treatments combined with 1.5 mg/mL of LC-EO. Transmission electron microscopy (TEM) was employed to determine morphological changes and the laser scanning confocal microscopy (LSCM) deducted the intracellular nucleic acid changes. The obtained results from TEM and LSCM indicated that the synergistic treatment can completely destroy E. coli O157:H7 cells via breaking the cell membrane. The detection of some intracellular substances, intracellular enzymes and metabolic capacity of bacteria also showed that synergistic treatment inhibits the activity of various intracellular enzymes of bacteria. The synergistic treatment of PMF and LC-EO maintained the number of bacteria close to 1 Log CFU/mL when the concentration of essential oil reduced from 3 mg/mL to 1.5 mg/mL and the PMF was 3 times under 8T, 60 pulses. Similarly, the combined treatment could also maintain the number of bacteria at a very low level in vegetable juice. Besides, the sensory evaluation exhibited that the combined treatment had no impact on the quality of vegetable juices. This work highlighted the huge prospect of collaborative processing. • The synergetic antibacterial activity of PMF and LC-EO against E. coli O157:H7 was studied. • The impacts on bacterial metabolism were found after synergistic treatment. • The synergistic treatment in vegetable juices showed excellent antibacterial effect. [ABSTRACT FROM AUTHOR]

Abstract Compared with traditional thermal sterilization process, pulsed magnetic field (PMF) is a non-thermal sterilization technology with superior advantages of maintaining the nutrition and flavor of food. But little is known about its antimicrobial mechanism. To explore its antimicrobial mechanism, the variation of cell membrane, intracellular biological macromolecules and respiratory metabolism of E. coli O157: H7 after PMF treatment, were investigated. The results showed that PMF could cause cell membrane damage and increase cell membrane permeability, reducing the content of three intracellular macromolecules (protein, ATP and DNA), as well as exhibiting inhibition for ATPase activity. The inhibition rate and superposition rate test confirmed the pathway that affecting the respiratory metabolism of E. coli O157:H7 treated with PMF was hexose monophophate pathway (HMP), via reducing the activity of key enzyme glucose-6-phosphate dehydrogenase in HMP. Besides, PMF also exhibited superior antibacterial effect on E. coli O157:H7 when it was applied in vegetable juices. Highlights • Pulsed Magnetic Field (PMF) can destroy the cell membrane of E. coli O157:H7. • PMF can inhibit Hexose Monophophate Pathway (HMP) in respiratory metabolic pathway. • PMF can be applied in vegetable juice sterilization without impact on quality. [ABSTRACT FROM AUTHOR]

Ultrasound technology has been focused on due to its unique advantages in biofilm removal compared with traditional antibacterial methods. Herein, the anti-biofilm properties of low-frequency ultrasound (LFUS) were studied against Enterohemorrhagic Escherichia coli O157: H7 (E. coli O157:H7). After ultrasonication (20 kHz, 300 W) for 5 min, the removal rate of biofilm from polystyrene sheets reached up to 99.999 %. However, the bacterial cells could not be inactivated completely even extending the duration of ultrasonic irradiation to 30 min. Fortunately, this study indicated that LFUS could efficiently weaken the metabolic capacity and biofilm-forming ability of bacterial cells separated from biofilm. It could be associated with the removal of cell surface appendages and damage to cell membrane induced by mechanical vibration and acoustic cavitation. Besides, the genetic analysis proved that the transcription level of genes involved in curli formation was significantly down-regulated during ultrasonic irradiation, thus impeding the process of irreversible adhesion and cells aggregation. Finally, the actual application effect of LFUS was also evaluated in different fresh produces model. The results of this study would provide a theoretical basis for the further application of ultrasound in the food preservation. • Low-frequency ultrasound (LFUS) was effective in removing E. coli O157:H7 biofilm. • LFUS inhibited the metabolic level and biofilm-forming ability of E. coli O157:H7. • LFUS down-regulated the transcription level of genes related to curli formation. • LFUS showed good anti-biofilm properties with application in fresh produce. [ABSTRACT FROM AUTHOR]

[Display omitted] • ECO/Zn2+ nanoparticles showed enhanced antibacterial activity against E. coli O157:H7. • Controlled-release ECO/Zn2+ nanoparticles with strong storage stability were prepared. • ECO might inhibit the metabolism and genetic material synthesis of E. coli O157:H7. • ECO/Zn2+ nanoparticles could be used as a promising natural agent in juice preservation. Eucalyptus citriodora oil (ECO) has excellent antibacterial properties, but its application is limited due to its volatility and lack of antimicrobial targeting properties. Zinc ions are metal ions on which the active center of metalloproteinases depend and have antibacterial functions. This study aimed to prepare nanoparticles against Escherichia coli O157:H7 (E. coli O157:H7) by encapsulating ECO in zein with nano-precipitation method, and chelating zinc metal ions with electrostatic interaction to improve the stability, controlled-release ability and antibacterial ability of nanoparticles. Herein, the antibacterial mechanism of ECO against E. coli O157:H7 was investigated from the molecular level. The results of molecular docking showed that ECO inhibited the activity of G6PDH in respiratory metabolism pathway (hexose monophophate pathway), and also inhibited the DNA polymerase. Furthermore, we demonstrated that the controlled-release nanoparticles (ECO/Zn2+-loaded NPT) possessed suitable particle size (275.43 nm), poly dispersity index (PDI, 0.254), zeta potential (-31.12 mV) and chelation rate (42.3 %). The results of Fourier Transform Infrared spectrometer (FT-IR), and Raman spectrum confirmed that ECO was successfully encapsulated in the nanoparticles. Meanwhile, the results of antibacterial experiments showed that ECO/Zn2+-loaded NPT possessed better antibacterial activity than ECO/zein nanoparticles. Finally, the test of application in fruit juice indicated that ECO/Zn2+-loaded NPT had no significant effect on physico-chemical properties and exhibited potential application in juice preservation. [ABSTRACT FROM AUTHOR]

Cinnamaldehyde (CA) possesses high antibacterial activity, but it's unstable and volatile in food system. To overcome its drawbacks, a kind of dual-response controlled-release nanofiber was fabricated by electrospinning to embed CA@hyaluronic acid/carboxymethyl chitosan nanoparticles (CA@HA/CMCS-NPs) into silk fibroin nanofibers (CA@HA/CMCS-NPs SF nanofibers). When the concentration of CA@HA/CMCS-NPs was 5 mg/mL, CA@HA/CMCS-NPs SF nanofibers have better mechanical properties, the tensile strength was 3.21 MPa, and the elongation at break was 47.51%. The β-glucuronidase (β-G) and serine protease specifically secreted by Escherichia coli (E. coli) O157:H7 could deconstruct the shell of SF and HA via hydrolysis. It results in the dual-response controlled-release of CA from CA@HA/CMCS-NPs SF nanofibers. After 5 days of treatment with CA@HA/CMCS-NPs SF nanofibers at 4 °C and 25 °C, the amount of E. coli O157:H7 in beef was reduced by 99.98% and 99.89%, respectively. Besides, the CA@HA/CMCS-NPs SF nanofibers have no impact on the sensory quality of beef. • The silk fibroin nanofibers loaded with CA@HA/CMCS-NPs were prepared. • A dual-response controlled-release of CA from nanofibers was achieved by bacterial secreta. • The nanofibers could specifically inhibit the activity of E. coli O157:H7 in beef. [ABSTRACT FROM AUTHOR]

• Multi-target antibacterial mechanism of Galangal root essential oil was explored. • Dominant compositions included ethyl cinnamate, methyl cinnamate, n-pentadecane. • P-type ATPases and glucose-6-phosphate dehydrogenase activities were inhibited. • Spectroscopic studies and molecular docking revealed the groove binding mode. In this research, the antibacterial activity and the interaction mechanisms of the major chemical constituent present in the Alpinia galanga rhizomes essential oil (AGREO) were investigated. Ethyl cinnamate, methyl cinnamate and n-pentadecane were the major components of AGREO. The antibacterial mechanism of AGREO on Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) was evaluated and the results proved that the potent antibacterial activity of AGREO was due to higher passive permeability of bacterial cell membrane, followed by crucial intracellular components efflux. Additionally, AGREO disrupted the intracellular physiological metabolism of EHEC O157, including inhibition of P-type ATPases activity and down-regulation expression of four virulence genes associated with EHEC infections. Notably, molecular docking studies suggested that ethyl cinnamate probably competed with the structural NAD(P)+ for the binding sites of glucose-6-phosphate dehydrogenase (G6PD), resulting in a decrease in G6PD activity with subsequent suppression of respiratory metabolism. The spectroscopic techniques and molecular docking studies proved that the AGREO major components were prone to bind to the minor groove of DNA. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes (L. monocytogenes) can adhere to biological or non-biological surfaces, including food processing equipment and storage containers. Subsequently, they can contaminate food by forming a biofilm, thereby causing serious food safety problems. In this project, the natural antibacterial agent clove essential oil (CEO) was selected to control L. monocytogenes biofilm, and the effect and mechanism of its action on the biofilm were explored in depth. TEM and CLSM observation results showed that CEO can destroy the dense membrane structure of the biofilm, thereby acting on the released free bacteria. Meanwhile, the study found that after CEO (2 Minimum biofilm inhibition concentration) treatment, the metabolic activity of the bacteria was reduced by 60.26%, and the secretion of extracellular polysaccharides and proteins was significantly inhibited. Besides, the CEO treatment can down-regulate the expression levels of the genes agrA , agrC , agrD , and prfA and up-regulate the expression level of the gene sigB , thereby regulating the formation of biofilms. Finally, CEO showed a significant removal effect on biofilms on different materials and vegetable surfaces. • CEO can inhibit the secretion of extracellular polysaccharides and proteins. • CEO can regulate the expression levels of genes related to L. monocytogenes biofilm formation. • CEO can effectively remove L. monocytogenes biofilm on vegetable surfaces. [ABSTRACT FROM AUTHOR]