Synergistic bactericidal effect of clove oil and encapsulated atmospheric pressure plasma against Escherichia coli O157:H7 and Staphylococcus aureus and its mechanism of action

Interaction between Enrofloxacin and Three Essential Oils (Cinnamon Bark, Clove Bud and Lavender Flower)-A Study on Multidrug-Resistant Escherichia coli Strains Isolated from 1-Day-Old Broiler Chickens

Avian pathogenic Escherichia coli (APEC) causes a variety of infections outside the intestine. The treatment of these infections is becoming increasingly difficult due to the emergence of multi-drug resistant (MDR) strains, which can also be a direct or indirect threat to humans as consumers of poultry products. Therefore, alternative antimicrobial agents are being sought, which could be essential oils, either administered individually or in interaction with antibiotics. Sixteen field isolates of E. coli (originating from 1-day-old broilers) and the ATCC 25922 reference strain were tested. Commercial cinnamon bark, clove bud, lavender flower essential oils (EOs) and enrofloxacin were selected to assess the sensitivity of the selected E. coli strains to antimicrobial agents. The checkerboard method was used to estimate the individual minimum inhibitory concentration (MIC) for each antimicrobial agent as well as to determine the interactions between the selected essential oil and enrofloxacin. In the case of enrofloxacin, ten isolates were resistant at MIC ≥ 2 μg/mL, three were classified as intermediate (0.5-1 μg/mL) and three as sensitive at ≤0.25 μg/mL. Regardless of the sensitivity to enrofloxacin, the MIC for cinnamon EO was 0.25% v/v and for clove EO was 0.125% v/v. All MDR strains had MIC values for lavender EO of 1% v/v, while drug-sensitive isolates had MIC of 0.5% v/v. Synergism between enrofloxacin and EO was noted more frequently in lavender EO (82.35%), followed by cinnamon EO (64.7%), than in clove EO (47.1%). The remaining cases exhibited additive effects. Owing to synergy, the isolates became susceptible to enrofloxacin at an MIC of ≤8 µg/mL. A time-kill study supports these observations. Cinnamon and clove EOs required for up to 1 h and lavender EO for up to 4 h to completely kill a multidrug-resistant strain as well as the ATCC 25922 reference strain of E. coli. Through synergistic or additive effects, blends with a lower than MIC concentration of enrofloxacin mixed with a lower EO content required 6 ± 2 h to achieve a similar effect.

Innovative Application of Cold Plasma Technology in Meat and Its Products

The growing demand for sustainable food production and the rising consumer preference for fresh, healthy, and safe food products have been driving the need for innovative methods for processing and preserving food. In the meat industry, this demand has led to the development of new interventions aimed at extending the shelf life of meats and its products while maintaining their quality and nutritional value. Cold plasma has recently emerged as a subject of great interest in the meat industry due to its potential to enhance the microbiological safety of meat and its products. This review discusses the latest research on the possible application of cold plasma in the meat processing industry, considering its effects on various quality attributes and its potential for meat preservation and enhancement. In this regard, many studies have reported substantial antimicrobial efficacy of cold plasma technology in beef, pork, lamb and chicken, and their products with negligible changes in their physicochemical attributes. Further, the application of cold plasma in meat processing has shown promising results as a potential novel curing agent for cured meat products. Understanding the mechanisms of action and the interactions between cold plasma and food ingredients is crucial for further exploring the potential of this technology in the meat industry, ultimately leading to the development of safe and high-quality meat products using cold plasma technology.

Emulsions containing composite (clove, oregano, and cinnamon) essential oils: Phase inversion preparation, physicochemical properties and antibacterial mechanism

Natural essential oils (EOs), especially those combining different individual EOs (also termed composite EOs) with enhanced performance, are becoming healthy, market-sought food preservatives/additives. This study aims to provide insights into the challenge regarding EOs processing due to their low solubility and the elusive mechanism under the enhanced bio-reactivity of composite EOs. A unique oil/water interacting network was created by phase-inversion processing, which enhances EO solubilization and emulsification to form composite EO formulations (EOFs) containing ordinary cinnamon, oregano and clove EOs. These EOFs mainly contained cinnamaldehyde, carvacrol and eugenol and exhibited excellent post-storage stability. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of EOFs (at 15.880 μL/mL) was > 88%, and the Ferric reducing antioxidant power (FRAP) was 1.8 mM FeSO₄·7H₂O. The minimum inhibitory concentration (MIC) of EOFs against E. coli and S. aureus was ∼7.940 μL/mL. The EOFs could cause quick deterioration of bacterial structures, demonstrating high efficacy in bacteria-killing and anti-biofilm formation.

Development and Evaluation of Essential Oil-Based Nanoemulgel Formulation for the Treatment of Oral Bacterial Infections

Prevalence of oral infections in diabetic patients is a health challenge due to persistent hyperglycemia. However, despite great concerns, limited treatment options are available. We therefore aimed to develop nanoemulsion gel (NEG) for oral bacterial infections based on essential oils. Clove and cinnamon essential oils based nanoemulgel were prepared and characterized. Various physicochemical parameters of optimized formulation including viscosity (65311 mPa·S), spreadability (36 g·cm/s), and mucoadhesive strength 42.87 N/cm²) were within prescribed limits. The drug contents of the NEG were 94.38 ± 1.12% (cinnamaldehyde) and 92.96 ± 2.08% (clove oil). A significant concentration of clove (73.9%) and cinnamon essential oil (71.2 %) was released from a polymer matrix of the NEG till 24 h. The ex vivo goat buccal mucosa permeation profile revealed a significant (52.7-54.2%) permeation of major constituents which occurred after 24 h. When subjected to antimicrobial testing, significant inhibition was observed for several clinical strains, namely Staphylococcus aureus (19 mm), Staphylococcus epidermidis (19 mm), and Pseudomonas aeruginosa (4 mm), as well as against Bacillus chungangensis (2 mm), whereas no inhibition was detected for Bacillus paramycoides and Paenibacillus dendritiformis when NEG was utilized. Likewise promising antifungal (Candida albicans) and antiquorum sensing activities were observed. It was therefore concluded that cinnamon and clove oil-based NEG formulation presented significant antibacterial-, antifungal, and antiquorum sensing activities.

Intrinsic properties and extrinsic factors of food matrix system affecting the effectiveness of essential oils in foods: a comprehensive review

Essential oils (EOs) have been proved as natural food preservatives because of their effective and wide-spectrum antimicrobial activity. They have been extensively explored for potential applications in food industry, and substantial progresses have been achieved. However well EOs perform in antibacterial tests in vitro, it has generally been found that a higher level of EOs is needed to achieve the same effect in foods. Nevertheless, this unsimilar effect has not been clearly quantified and elaborated, as well as the underlying mechanisms. This review highlights the influence of intrinsic properties (e.g., oils and fats, carbohydrates, proteins, pH, physical structure, water, and salt) and extrinsic factors (e.g., temperature, bacteria characteristics, and packaging in vacuum/gas/air) of food matrix systems on EOs action. Controversy findings and possible mechanism hypotheses are also systematically discussed. Furthermore, the organoleptic aspects of EOs in foods and promising strategies to address this hurdle are reviewed. Finally, some considerations about the EOs safety are presented, as well as the future trends and research prospects of EOs applications in foods. The present review aims to fill the evidenced gap, providing a comprehensive overview about the influence of the intrinsic and extrinsic factors of food matrix systems to efficiently orientate EOs applications.

Dual-functionalized Pickering HIPE templated poly(ɛ-caprolactone) scaffold for maxillofacial implants

High internal phase emulsion (HIPE) templated poly (ɛ-caprolactone) (PCL) scaffolds have gained widespread attention for large-sized bone defects due to its tuneable 3D architecture and ease of fabricating crosslinked PCL (cPCL) scaffolds. However, extremely high stabilizer (surfactant or nanoparticle) concentration and negligence of microenvironment for regeneration sites like alveolar bones have restrained industrial acceptance of these scaffolds. Herein, we demonstrated the fabrication of nanocomposite cPCL scaffolds within Pickering HIPE templates stabilized using modified silica nanoparticles (mSiNP) concentrations as low as 0.1 to 1.0 wt%. Using an unconventional approach, the mSiNP Pickering stabilizer was added in dispersed phase, contradicting Bancroft's rule. The colloidal stability was attained due to faster drifting of mSiNP towards the interface when it was dispersed in silicone oil. Scaffolds with tuneable properties were fabricated by controlling the mSiNP concentration and ϕ_d. Further, cPCL scaffolds were functionalized using clove oil (CO) to improve their efficiency in eradicating S. aureus and E. coli by disrupting their cellular integrity. Additionally, formation of biofilm on the surface of the scaffolds was successfully inhibited by the incorporation of CO. CO-functionalized scaffolds demonstrated excellent cytocompatibility towards MG-63 cells allowing their successful adhesion and proliferation on the surface of the scaffolds.

Structural Analysis and Antimicrobial Mechanism of a Protein GBSPI-A from Ginkgo Biloba Seed

Ginkgo biloba seed has antimicrobial activity. In this study, ginkgo biloba seed protein was prepared, identified, and named GBSPI-A, finding its construction was similar to 11-S globulin. Then, the influence of GBSPI-A on the cell membrane and physiological metabolism of K. pneumoniae and S. aureus were investigated. The results showed that GBSPI-A (20 mg/mL) destroyed the cell membrane, causing leakage of intracellular material and inhibited bacterial growth with an inhibition rate of approximately 80%. In addition, the GBSPI-A (10 mg/mL) caused the decreasing activity of ATPase and respiratory rate, and the respiratory depression rate was 7.24%. Furthermore, the decreasing ATP synthesis and intracellular β-galactosidase activity led to an insufficient supply of physiological metabolic energy. Therefore, the results showed that GBSPI-A could be used as a natural bacteriostatic agent to replace related drugs and also provide a new insight into the application of GBSPI-A in food safety.

Multitarget preservation technologies for chemical-free sustainable meat processing

Due to the growing consumer demand for safe and naturally processed meats, the meat industry is seeking novel methods to produce safe-to-consume meat products without affecting their sensory appeal. The green technologies can maintain the sensory and nutritive characteristics and ensure the microbial safety of processed meats and, therefore, can help to reduce the use of chemical preservatives in meat products. The use of chemical additives, especially nitrites in processed meat products, has become controversial because they may form carcinogenic N-nitrosamines, a few of which are suspected as cancer precursors. Thus, the objective of reducing or eliminating nitrite is of great interest to meat researchers and industries. This review, for the first time, discusses the influence of processing technologies such as microwave, irradiation, high-pressure thermal processing (HPTP) and multitarget preservation technology on the quality characteristics of processed meats, with a focus on their sensory quality. These emerging technologies can help in the alleviation of ingoing nitrite or formed nitrosamine contents in meat products. The multitarget preservation technology is an innovative way to enhance the shelf life of meat products through the combined use of different technologies/natural additives. The challenges and opportunities associated with the use of these technologies for processing meat are also reviewed.

Nanoemulsion as an Effective Inhibitor of Biofilm-forming Bacterial Associated Drug Resistance: An Insight into COVID Based Nosocomial Infections

Antibiotic overuse has resulted in the microevolution of drug-tolerant bacteria. Understandably it has become one of the most significant obstacles of the current century for scientists and researchers to overcome. Bacteria have a tendency to form biofilm as a survival mechanism. Biofilm producing microorganism become far more resistant to antimicrobial agents and their tolerance to drugs also increases. Prevention of biofilm development and curbing the virulency factors of these multi drug resistant or tolerant bacterial pathogens is a newly recognised tactic for overcoming the challenges associated with such bacterial infections and has become a niche to be addressed. In order to inhibit virulence and biofilm from planktonic bacteria such as, Pseudomonas aeruginosa, Acinetobacter baumannii, and others, stable nanoemulsions (NEs) of essential oils (EOs) and their bioactive compounds prove to be an interesting solution. These NEs demonstrated significantly greater anti-biofilm and anti-virulence activity than commercial antibiotics. The EO reduces disease-causing gene expression, which is required for pathogenicity, biofilm formation and attachment to the surfaces. Essential NE and NE-loaded hydrogel surface coatings demonstrates superior antibiofilm activity which can be employed in healthcare-related equipments like glass, plastic, and metal chairs, hospital beds, ventilators, catheters, and tools used in intensive care units. Thus, anti-virulence and anti-biofilm forming strategies based on NEs-loaded hydrogel may be used as coatings to combat biofilm-mediated infection on solid surfaces.

Metabolomic Profile and Antibacterial Bioactivity of Akebia trifoliata (Thunb.) Koidz Pericarp Extract

Akebia trifoliata (A. trifoliata) is a significant medicinal and edible fruit crop and has some important bioactivities. However, there are few studies on the bacteriostatic activity of A. trifoliata, and the underlying mechanism of A. trifoliata for antibacterial activity is still unknown. Therefore, the bacteriostatic activity and antibacterial mechanism of A. trifoliata were investigated by a combination of chemical assays, using the UHPLC-TOF-MS/MS technique. The results indicated that alkaloids, triterpenoids, and flavonoids are the major secondary bioactive compounds in A. trifoliata that play a crucial role in antibacterial activity. We found that EEPA exhibited both bacteriostatic and bactericidal effects against all Gram-positive and Gram-negative bacteria tested, with IZDs ranging from 13.80 ± 0.79 to 17.00 ± 0.58 mm. Significant differences in terms of sensitivity between Gram-positive and Gram-negative bacteria were not observed. In contrast, both antibiotics (kanamycin sulfate and ampicillin sodium salt) exhibited much better antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria. In addition, the primary antimicrobial mechanism was that EEPA increased cellular content leakage, altered the cell morphology, and destroyed the internal cell structure. Meanwhile, MA, UA, and OA, as the common triterpenoid components existing in plants, were used to analyze the relationships between the structures and the antimicrobial activities among homologous compounds, to determine the key functional group that plays an antibacterial role in MA, UA, and OA. As result, it was found that both the hydroxide and methyl groups present are important for their antibacterial activity. These findings suggested that EEPA exerted significant antimicrobial activity against S. aureus, E. coli, B. subtilis, and P. aeruginosa and might be a potential natural antibacterial.

Emulsifying properties and bioavailability of clove essential oil Pickering emulsions stabilized by octadecylaminated carboxymethyl curdlan

In the present study, clove essential oil (CEO) Pickering emulsions were stabilized by octadecylamine-modified carboxymethyl curdlan (CMCD-ODA) at different pH values. The droplet size and negatively charged zeta potential of the CMCD-ODA emulsions decreased as the pH increased from 3.0 to 11.0. Rheology results indicated that the CMCD-ODA polymer/emulsion prepared at pH 5.0 showed higher apparent viscosity and viscoelasticity than other pH conditions, which might prevent droplets from flocculating. The Pickering emulsions obtained at pH 5.0 were spherical droplets with a uniform size distribution and a mean diameter of 9.54 μm, and they exhibited excellent stability during 28 days of storage. The morphological structures of the emulsions investigated by confocal laser scanning microscopy and scanning electron microscopy indicated that the CMCD-ODA Pickering emulsion obtained at pH 5.0 was stabilized by loading amphiphilic CMCD-ODA polymer around the spherical oil droplets and forming a weak gel network structure. The CEO-loaded CMCD-ODA emulsions had higher antioxidant capacity than free CEO after 28 days of storage at pH 5.0. Given the good emulsion stability, antioxidant activity, and great antibacterial effect, the CEO-loaded carboxymethyl curdlan Pickering emulsion has promising applications in food, cosmetic, and biomedicine industries.

Recent Advances and Potential Applications of Atmospheric Pressure Cold Plasma Technology for Sustainable Food Processing

In a circular economy, products, waste, and resources are kept in the system as long as possible. This review aims to highlight the importance of cold plasma technology as an alternative solution to some challenges in the food chain, such as the extensive energy demand and the hazardous chemicals used. Atmospheric cold plasma can provide a rich source of reactive gas species such as radicals, excited neutrals, ions, free electrons, and UV light that can be efficiently used for sterilization and decontamination, degrading toxins, and pesticides. Atmospheric cold plasma can also improve the utilization of materials in agriculture and food processing, as well as convert waste into resources. The use of atmospheric cold plasma technology is not without challenges. The wide range of reactive gas species leads to many questions about their safety, active life, and environmental impact. Additionally, the associated regulatory approval process requires significant data demonstrating its efficacy. Cold plasma generation requires a specific reliable system, process control monitoring, scalability, and worker safety protections.

Antimicrobial behavior and mechanism of clove oil nanoemulsion

Clove oil has many functions such as antibacterial, anti-inflammatory, anti-oxidation. In this experiment, a self-emulsification method was used to prepare clove oil nanoemulsion. And then filter paper diffusion method, minimum inhibitory concentration, and minimum bactericidal concentration were used to study the inhibitory behavior of clove oil nanoemulsion on Escherichia coli and Staphylococcus aureus. And explore the antibacterial mechanism by dynamically testing the content of nucleic acid and protein in the culture solution during the antibacterial process. The results show that when the surfactant content is 10 wt%, the hydrophile-lipophile balance (HLB) is 13.93, and the oil phase content is 2 wt%, a clove oil nanoemulsion with better dispersion and smaller average particle size can be prepared. The minimum inhibitory concentration (MIC) of clove oil nanoemulsion against Escherichia coli and Staphylococcus aureus is 0.5, 0.25 mg/mL, and the minimum bactericidal concentration (MBC) is 1, 2 mg/mL. The increase in protein content and the exponential growth of nucleic acid release also indicated that the clove oil nanoemulsion destroys the integrity of the cell membrane. The experimental results can provide a reference for the application of clove oil nanoemulsion in food, medicine and other fields.

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Antibacterial Mode of Eucommia ulmoides Male Flower Extract Against Staphylococcus aureus and Its Application as a Natural Preservative in Cooked Beef

The research was conducted to elucidate the antibacterial performance and mode of action of Eucommia ulmoides male flower extract (EUMFE) against Staphylococcus aureus and its application as a natural preservative in cooked beef. The antibacterial activity was evaluated by determining the diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), and minimum bactericide concentration (MBC). The changes in membrane potential, contents of bacterial DNA and protein, integrity and permeability of the cell membrane, and cell morphology were analyzed to reveal the possible mode of action. The effect of EUMFE on the counts of S. aureus, pH, color, total volatile basic nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARS) of the cooked beef stored at 4°C for 9 days were studied. The results showed that the DIZ, MIC, and MBC of EUMFE against S. aureus were 12.58 ± 0.23 mm, 40 mg/mL, and 80 mg/mL, respectively. The mode of action of EUMFE against S. aureus included hyperpolarization of cell membrane, decrease in bacterial DNA and protein contents, destruction of cell membrane integrity, increase in cell membrane permeability, and damage of cell morphology. After treatments with EUMFE, the growth of S. aureus and lipid oxidation in cooked beef were significantly inhibited (P < 0.05). The pH and TVB-N values of cooked beef treated with EUMFE were significantly reduced as compared to control group (P < 0.05). The color of cooked beef samples containing EUMFE showed decreased L* and b* values, and increased a* and ΔE* values. Therefore, our findings showed that EUMFE had a good antibacterial effect on S. aureus, and provided a theoretical basis for the application of EUMFE as a natural preservative in the preservation of cooked beef.

Comparative Transcriptomic Analysis of Staphylococcus aureus Reveals the Genes Involved in Survival at Low Temperature

In food processing, the temperature is usually reduced to limit bacterial reproduction and maintain food safety. However, Staphylococcus aureus can adapt to low temperatures by controlling gene expression and protein activity, although its survival strategies normally vary between different strains. The present study investigated the molecular mechanisms of S. aureus with different survival strategies in response to low temperatures (4 °C). The survival curve showed that strain BA-26 was inactivated by 6.0 logCFU/mL after 4 weeks of low-temperature treatment, while strain BB-11 only decreased by 1.8 logCFU/mL. Intracellular nucleic acid leakage, transmission electron microscopy, and confocal laser scanning microscopy analyses revealed better cell membrane integrity of strain BB-11 than that of strain BA-26 after low-temperature treatment. Regarding oxidative stress, the superoxide dismutase activity and the reduced glutathione content in BB-11 were higher than those in BA-26; thus, BB-11 contained less malondialdehyde than BA-26. RNA-seq showed a significantly upregulated expression of the fatty acid biosynthesis in membrane gene (fabG) in BB-11 compared with BA-26 because of the damaged cell membrane. Then, catalase (katA), reduced glutathione (grxC), and peroxidase (ahpC) were found to be significantly upregulated in BB-11, leading to an increase in the oxidative stress response, but BA-26-related genes were downregulated. NADH dehydrogenase (nadE) and α-glucosidase (malA) were upregulated in the cold-tolerant strain BB-11 but were downregulated in the cold-sensitive strain BA-26, suggesting that energy metabolism might play a role in S. aureus under low-temperature stress. Furthermore, defense mechanisms, such as those involving asp23, greA, and yafY, played a pivotal role in the response of BB-11 to stress. The study provided a new perspective for understanding the survival mechanism of S. aureus at low temperatures.

In Vitro Antibacterial Mechanism of High-Voltage Electrostatic Field against Acinetobacter johnsonii

This study aimed to investigate the antibacterial properties and mechanisms of a high-voltage static electric field (HVEF) in Acinetobacter johnsonii, which were assessed from the perspective of biochemical properties and stress-related genes. The time/voltage-kill assays and growth curves showed that an HVEF decreased the number of bacteria and OD600 values. In addition, HVEF treatment caused the leakage of cell contents (nucleic acids and proteins), increased the electrical conductivity and amounts of reactive oxygen substances (ROS) (16.88 fold), and decreased the activity of Na+ K+-ATPase in A. johnsonii. Moreover, the changes in the expression levels of genes involved in oxidative stress and DNA damage in the treated A. johnsonii cells suggested that HVEF treatment could induce oxidative stress and DNA sub-damage. This study will provide useful information for the development and application of an HVEF in food safety.

Effect of plasma-activated acetic acid on inactivation of Salmonella Typhimurium and quality traits on chicken meats

This study investigated the bactericidal effects of plasma-activated acetic acid (PAAA) on Salmonella Typhimurium and its impact on the physicochemical traits of chicken meat. Twenty milliliters of 0.8% (v/v) acetic acid (AA) was treated with plasma (2.2 kHz and 8.4 kVpp) for 30 min. The chicken skins, breasts, and drumsticks, inoculated with S. Typhimurium, were immersed in AA or PAAA and incubated for 10 min. The S. Typhimurium on the breasts and drumsticks were significantly susceptible to treatment with AA and PAAA, compared to the control group (deionized water treatment), and the population of bacterial cells in PAAA-treated chicken breasts and drumsticks decreased by 0.98 and 1.19 log CFU/g, respectively, compared with AA. The values for pH and 2-thiobarbituric acid reactive substances (TBARS) of PAAA-treated samples decreased significantly compared to the control group. The lightness (L*) values of the chicken breasts after AA and PAAA treatments increased compared to the control group, whereas the value for yellowness (b*) decreased. The scanning electron microscopic (SEM) images and the results for volatile compounds in chicken meat revealed similar patterns, with no significant differences between AA and PAAA treatments. In conclusion, we found that PAAA was more effective than AA and synergistic PAAA treatment of chicken caused to the reduction of S. Typhimurium and improve the meat quality. Therefore, PAAA could be utilized as a promising decontaminant for the chicken meat industry.

Response characteristics of the membrane integrity and physiological activities of the mutant strain Y217 under exogenous butanol stress

Butanol inhibits bacterial activity by destroying the cell membrane of Clostridium acetobutylicum strains and altering functionality. Butanol toxicity also results in destruction of the phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS), thereby preventing glucose transport and phosphorylation and inhibiting transmembrane transport and assimilation of sugars, amino acids, and other nutrients. In this study, based on the addition of exogenous butanol, the tangible macro indicators of changes in the carbon ion beam irradiation-mutant Y217 morphology were observed using scanning electron microscopy (SEM). The mutant has lower microbial adhesion to hydrocarbon (MATH) value than C. acetobutylicum ATCC 824 strain. FDA fluorescence intensity and conductivity studies demonstrated the intrinsically low membrane permeability of the mutant membrane, with membrane potential remaining relatively stable. Monounsaturated FAs (MUFAs) accounted for 35.17% of the mutant membrane, and the saturated fatty acids (SFA)/unsaturated fatty acids (UFA) ratio in the mutant cell membrane was 1.65. In addition, we conducted DNA-level analysis of the mutant strain Y217. Expectedly, through screening, we found gene mutant sites encoding membrane-related functions in the mutant, including ATP-binding cassette (ABC) transporter-related genes, predicted membrane proteins, and the PTS transport system. It is noteworthy that an unreported predicted membrane protein (CAC 3309) may be related to changes in mutant cell membrane properties. KEY POINTS: • Mutant Y217 exhibited better membrane integrity and permeability. • Mutant Y217 was more resistant to butanol toxicity. • Some membrane-related genes of mutant Y217 were mutated.

Synthesis of novel 2-methyl-3-furyl sulfide flavor derivatives as efficient preservatives

Foodborne microbial infestation seriously threatens food security, and the development of low-risk food preservatives is highly needed in food production. For discovering novel flavor molecules with antiseptic function, novel 2-methyl-3-furyl sulfide flavor derivatives were synthesized and evaluated. A wide range of 2-methyl-3-furyl sulfide derivatives were synthesized by reactions of 2-methyl-3-furyl disulfide with cyclic ethers, amides, ketones, and epoxides. All of these compounds have special aroma characteristics and low aroma thresholds. The antimicrobial activity of these compounds against test foodborne bacterial or fungal strains (Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Salmonella paratyphi, Listeria monocytogenes, Vibrio parahemolyticus, Penicillium italicum, Aspergillus niger, Mucor racemosus, Rhizopus oryzae) was examined. It was found that fifteen compounds (3a, 3b, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 3k, 3l, 3m, 5a, 5b, 5f) have antimicrobial activity against different foodborne bacterial or fungal strains. Significantly, the antimicrobial activity of the flavor compounds (3b, 3d, 3e, 3i, 3j, 3l, 3m) is better than that of the control group (penicillin, amphotericin B and thiram), and they are promising preservatives for food production.

Foodborne microbial infestation seriously threatens food security, and the development of low-risk food preservatives is highly needed in food production.

Inactivation of Salmonella Typhimurium by Non-Thermal Plasma Bubbles: Exploring the Key Reactive Species and the Influence of Organic Matter

The key reactive species generated by non-thermal plasma bubbles for the inactivation of Salmonella Typhimurium and the effects of organic matter on the inactivation efficacy were investigated. Plasma, which is primarily composed of ozone (O₃), was generated by dielectric barrier discharge and injected into a solution (400 mL) as a bubble. The surviving population of S. Typhimurium decreased in proportion to the treatment time, resulting in a 5.29 log reduction after 5 min of treatment. Verification tests to specify key reactive species were conducted using an O₃ destruction unit and reactive oxygen species scavengers. The results indicated that singlet oxygen (¹O₂) contributes substantially to the inactivation of S. Typhimurium, and that the presence of superoxide anion radicals (O₂^·−) from O₃ is essential for the production of ¹O₂. When a S. Typhimurium suspension containing organic matter (final concentration: 0, 0.005, 0.05, 0.1, and 0.5 g/L), consisting of beef extract and peptone, was treated with plasma bubbles for 5, 10, 15, 20, 25, and 30 min, respectively, the potential of the plasma bubbles for inactivating S. Typhimurium successfully was verified with longer contact time, despite organic matter attenuating the inactivation efficiency in a dose-dependent manner.