Antimicrobial effects of modified chitosan based coating containing nanoemulsion of essential oils, modified atmosphere packaging and gamma irradiation against Escherichia coli O157:H7 and Salmonella Typhimurium on green beans

Phytohormones in postharvest storage of fruit and vegetables: mechanisms and applications

As a ubiquitous and essential part of phytophysiology, phytohormones have attracted tremendous attention for effective regulation of development and senescence of agricultural products. However, the postharvest mechanisms of phytohormones have not been thoroughly understood. This review provides an overview of common phytohormones for extending the shelf life of fruit and vegetables. The modulation principles are discussed in detail based on defence gene expression activation, sensitivity of senescence-related phytohormones inhibition, antioxidant enzymes activity stimulation, and cell membrane integrity maintenance. The applications of jasmonates, salicylic acids, cytokinins, gibberellins, polyamines, and brassinosteroids in preserving fruit and vegetables based on defence signaling network stimulation, senescence-related phytohormones expression or sensitivity repression, as well as antioxidant system enhancement and cell membrane integrity sustentation are introduced. The challenges and problems to be solved are discussed, and new trends of expanding lifespan by combining phytohormones with other treatments are also suggested. Although phytohormones have been demonstrated to have promising efforts in maintaining agricultural products, more novel and effective combination treatments should be developed to complement each other.

Applications of chitosan and chitosan based metallic nanoparticles in agrosciences-A review

The second most abundant biological macromolecule, next to cellulose is Chitosan. It is a versatile naturally occurring hydrophilic polysaccharide, derived as a deacetylated form of chitin. Due to its biocompatibility, biodegradability and antimicrobial activity, it has become a significant area of research towards drug delivery system, plant growth promotion, anti-pathogenic potentiality, seed priming and in plant defense mechanism. Various synthetic strategies have been established in recent years that couples different metals with chitosan nanoparticles. Metals like silver, copper, zinc, iron and nickel are highly compatible to form chitosan metallic nanoparticles and are proved to be non-toxic to the agricultural plant system. This review highlights the mode of action of nanochitosan on Gram-positive and Gram-negative bacteria in a distinguished manner as well as its action on fungi. A prime focus has been given on the skeletal framework of the metallic nanochitosan particles. Our study also projects the antimicrobial mechanism of chitosan based on its physiochemical properties, environmental factors and the type of organism on which it acts. Moreover, the mechanism for stimulation of plant immunity by metallic nanochitosan has also been reviewed. Our study relies on the conclusion that chitosan metallic nanoparticles showed enhanced anti-pathogenic and plant growth promoting activity in comparison to bulk chitosan.

Rheological Behavior, Antimicrobial and Quorum Sensig Inhibition Study of an Argentinean Oregano Essential Oil Nanoemulsion

In this study, Argentinean oregano essential oil (OEO) nanoemulsions (NEs) were developed. Four NEs were prepared: a control (CNE), EONE1 (10.6 mg EO/g NE), EONE2 (106 mg EO/ g NE), and EONE3 (160 mg EO/g NE) and tested for antimicrobial activity against Staphylococcus aureus ATCC 13565, Listeria monocytogenes Scott A, Pseudomonas aeruginosa ATCC 14213, and Escherichia coli O157:H7 using a broth microdilution assay and quorum sensing inhibition in a model using Chromobacterium violaceum ATCC 12472, where the production of violacein was quantified. The chemical composition of the EO was determined by gas chromatography-mass spectrometry. The average particle size (nm) and polydispersity index were monitored over 14 days at two different storage temperatures (4 and 23°C). A rheological behavior study was carried out using a dynamic shear rheometer, and flow curves, as well as viscoelastic properties, were determined. E. coli and L. monocytogenes were the most sensitive microorganisms to EONE (MIC of 2 and 5 mg/ml for EOEN3). Sub-MICs for NE were found at lower concentrations than those for pure EO. A significant reduction in violet pigment intensity and colorless coloration (p < 0.05) were observed at different NE concentrations concerning the control sample. The flow behavior index (n) decreased, and the consistency index (k) increased when the EO concentration was increased. CNE, EONE1, and EONE2 showed liquid-like behavior (G' < G″) in the low-frequency region, whereas a solid-like behavior (G' > G″) was observed in the high-frequency region, presenting a viscoelastic behavior, appearing as a wormlike micellar solution. For EONE3, a strong increase in both moduli was observed with increasing OEO concentration. The G' was about one order of magnitude higher than the G″ over the whole frequency range, indicating the presence of a gel-like structure. The incorporation of EOs into an NE increased their stability, lowering the particle size, leading to a wormlike micelle with higher viscosity. Moreover, this NE had good antimicrobial activity and novel quorum-sensing inhibition activity. The results of this study indicated that Argentinean OEO NE could be used in a food system as a natural and stable antimicrobial agent.

Effect of Some Citrus Essential Oils on Post-Harvest Shelf Life and Physicochemical Quality of Strawberries during Cold Storage

Utilization of essential oils alone or incorporation with edible films is an appropriate technique to conserve the quality attributes and reduce post-harvest deterioration in fresh vegetables and fruits. Strawberries, being perishable fruits have a short shelf life, and using essential oils is considered one of the most suitable methods to prolong their shelf life during storage. The current study assessed the impact of different essential oils, including lemon oil (L), orange oil (O) and mandarin oil (M) on the physicochemical and microbial load of strawberries (Fragaria × ananassa cv. Festival) stored at 2 ± 1 °C and 95% relative humidity (RH) for 18 days. The differences in the physicochemical and microbial properties of strawberries were assessed by determining the following parameter changes: weight loss, decay percentage, firmness, soluble solids content, titratable acidity, color, anthocyanins, vitamin C, total phenol, total antioxidant, catalase activity, polyphenol oxidase activity, sensory evaluation, microbial content, total coliforms, molds, and yeasts. The results of this study indicated that the fruits treated with all essential oils treatments (L, O and M) had higher total antioxidant content and physicochemical properties than untreated fruits, due to protection against the microbial growth of molds, and yeasts. At the end of the storage period, the treated fruits showed a greater acceptance and sensory attributes than the untreated fruits. Furthermore, the correlation study showed a significant and negative relationship between the total antioxidant of treated fruits and following quality attributes including, weight loss, decay percentage, respiration rate soluble solids content, polyphenol oxidase activity, molds, and yeasts. It is noteworthy that all the essential oil treatments extended the shelf-life of strawberries and delayed their deterioration up to 18 days.

Edible Coating and Pulsed Light to Increase the Shelf Life of Food Products

The application of edible coatings (EC) in combination with pulsed light (PL) treatments represents an emerging approach for extending the shelf life of highly perishable but high value-added products, such as fresh-cut fruits and vegetables. The surface of these products would benefit from the protective effects of ECs and the PL decontamination capability. This review describes in detail the fundamentals of both EC and PL, focusing on the food engineering principles in the formulation and application of EC and the delivery of efficient PL treatments and the technological aspects related to the food characterization following these treatments and discussing the implementation of the two technologies, individually or in combination. The advantages of the combination of EC and PL are extensively discussed emphasizing the potential benefits that may be derived from their combination when preserving perishable foods. The downsides of combining EC and PL are also presented, with specific reference to the potential EC degradation when exposed to PL treatments and the screening effect of PL transmittance through the coating layer. Finally, the potential applications of the combined treatments to food products are highlighted, comparatively presenting the treatment conditions and the product shelf-life improvement.

Antimicrobial activity of chitosan coating containing ZnO nanoparticles against E. coli O157:H7 on the surface of white brined cheese

White brined cheese may serve as an ideal medium for the growth of foodborne pathogens including E. coli O157:H7. The objectives of this study were i) to evaluate the inhibitory effects of zinc oxide (ZnO) nanoparticles against E. coli O157:H7 at 10 or 37 °C using broth dilution; ii) to address the post-process contamination of white brined cheese with E. coli O157:H7 by using chitosan coating with or without ZnO nanoparticles during storage for 28 d at 4 and 10 °C; and iii) to study the physicochemical characteristics of chitosan coating containing ZnO nanoparticles. ZnO nanoparticles at ≥0.0125% inhibited the growth of three E. coli O157:H7 strains at both 37 and 10 °C. The chitosan coating with or without ZnO nanoparticles significantly reduced the initial numbers of E. coli O157:H7 in white brined cheese by 2.5 and 2.8 log CFU/g, respectively, when stored at 4 °C or by 1.9 and 2.1 log CFU/g, respectively, when stored at 10 °C. The chitosan-ZnO nanoparticle coating was not significantly different (p > 0.05) but was slightly better than chitosan alone as an active, smart packaging material in food applications.

Edible and Functionalized Films/Coatings—Performances and Perspectives

In recent years, food packaging has evolved from an inert and polluting waste that remains after using the product toward an active item that can be consumed along with the food it contains. Edible films and coatings represent a healthy alternative to classic food packaging. Therefore, a significant number of studies have focused on the development of biodegradable enveloping materials based on biopolymers. Animal and vegetal proteins, starch, and chitosan from different sources have been used to prepare adequate packaging for perishable food. Moreover, these edible layers have the ability to carry different active substances such as essential oils—plant extracts containing polyphenols—which bring them considerable antioxidant and antimicrobial activity. This review presents the latest updates on the use of edible films/coatings with different compositions with a focus on natural compounds from plants, and it also includes an assessment of their mechanical and physicochemical features. The plant compounds are essential in many cases for considerable improvement of the organoleptic qualities of embedded food, since they protect the food from different aggressive pathogens. Moreover, some of these useful compounds can be extracted from waste such as pomace, peels etc., which contributes to the sustainable development of this industry.

Bergamot essential oil nanoemulsions: antimicrobial and cytotoxic activity

Bergamot essential oil (BEO) is well-known for its food preservation activity, as well as anticancer efficacy. However, the poor BEO water solubility and deriving low bioaccessibility have limited its wider applications. The incorporation in nanoemulsions of BEO and its refined fractions was investigated to enhance its dispersibility in water to promote its antimicrobial activity, tested against Escherichia coli, Lactobacillus delbrueckii, and Saccharomyces cerevisiae, and its cytotoxicity already at low concentrations. Different nanoemulsion formulations were tested based on food-grade ingredients, which were characterized in terms of hydrodynamic diameter and polydispersity index, and physical stability. The antimicrobial activity against all the tested micro-organisms was observed to be higher for BEO in its initial composition, than the light fraction, richer in d-limonene, ß-pinene, and γ-terpinene, or the heavy fraction, richer in linalyl acetate and linalool. Remarkably, the use of BEO nanoemulsions notably enhanced the antimicrobial activity for all the tested oils. BEO exhibited also a measurable cytotoxic activity against Caco-2 cells, which was also enhanced by the use of the different nanoemulsions tested, in comparison with free oil, which discourages the direct use of BEO nanoemulsions as a food preservative. Conversely, BEO nanoemulsions might find use in therapeutic applications as anticarcinogenic agents.

The Role of Essential Oils against Pathogenic Escherichia coli in Food Products

Outbreaks related to foodborne diseases are a major concern among health authorities, food industries, and the general public. Escherichia coli (E. coli) is a pathogen associated with causing multiple outbreaks in the last decades linked to several ready to eat products such as meat, fish, dairy products, and vegetables. The ingestion of contaminated food with pathogenic E. coli can cause watery diarrhea, vomiting, and persistent diarrhea as well as more severe effects such as hemorrhagic colitis, end-stage renal disease, and, in some circumstances, hemolytic uremic syndrome. Essential oils (EOs) are natural compounds with broad-spectrum activity against spoilage and pathogenic microorganisms and are also generally recognized as safe (GRAS). Particularly for E. coli, several recent studies have been conducted to study and characterize the effect to inhibit the synthesis of toxins and the proliferation in food systems. Moreover, the strategy used to apply the EO in food plays a crucial role to prevent the development of E. coli. This review encompasses recent studies regarding the protection against pathogenic E. coli by the use of EO with a major focus on inhibition of toxins and proliferation in food systems.

Antimicrobial-loaded nanocarriers for food packaging applications

Increasing the demands of consumers for organic and safer foods has led to applying new technologies for food preservation. Active packaging (AP) containing natural antimicrobial agents is a good candidate for promoting the shelf life of food products. The efficiency of AP has been enhanced through nanoencapsulation methods, in which antimicrobial-loaded nanocarriers could provide a controlled release of antimicrobial active packaging for keeping the quality of foods during storage. The main objective of this review is to introduce common methods for designing novel encapsulation delivery systems offering controlled release of antimicrobials in the AP systems. The common nanocarriers for enveloping antimicrobial agents are described and the current state of art in the application of nanoencapsulated antimicrobials in development of antimicrobial APs have been summarized and tabulated. Incorporation of a carrier loaded with natural antimicrobial agents is the most effective method for developing AP in the food packaging sector which has become possible by using nanoencapsulated antimicrobials in films or coating structures, instead of using their free form. Nanoencapsulation approaches provide many advantages including protection against environmental stresses, release control, and improving the solubility and absorption of natural antimicrobials in AP, which are the main achievements overcoming the barriers for using natural antimicrobials in food packaging.

Citrus Essential Oils (CEOs) and Their Applications in Food: An Overview

Citrus is a genus belonging to the Rutaceae family and includes important crops like orange, lemons, pummelos, grapefruits, limes, etc. Citrus essential oils (CEOs) consist of some major biologically active compounds like α-/β-pinene, sabinene, β-myrcene, d-limonene, linalool, α-humulene, and α-terpineol belonging to the monoterpenes, monoterpene aldehyde/alcohol, and sesquiterpenes group, respectively. These compounds possess several health beneficial properties like antioxidant, anti-inflammatory, anticancer, etc., in addition to antimicrobial properties, which have immense potential for food applications. Therefore, this review focused on the extraction, purification, and detection methods of CEOs along with their applications for food safety, packaging, and preservation. Further, the concerns of optimum dose and safe limits, their interaction effects with various food matrices and packaging materials, and possible allergic reactions associated with the use of CEOs in food applications were briefly discussed, which needs to be addressed in future research along with efficient, affordable, and "green" extraction methods to ensure CEOs as an ecofriendly, cost-effective, and natural alternative to synthetic chemical preservatives.

Preservative Effects of Gelatin Active Coating Containing Eugenol and Higher CO2 Concentration Modified Atmosphere Packaging on Chinese Sea bass (Lateolabrax maculatus) during Superchilling (-0.9 °C) Storage

The purpose of this research was to explore the fresh keeping effect of modified atmosphere packaging (MAP) with different gas ratios combined with gelatin active coatings containing eugenol on Chinese sea bass stored at −0.9 °C for 36 days. The results showed that MAP3 (60% CO₂/10% O₂/30% N₂), together with gelatin active coatings containing eugenol, could prevent water loss, which maintained high field NMR, MRI, and organoleptic evaluation results. This hurdle technology could also effectively delay the bacterial reproduction, protein degradation, and alkaline accumulation, so it showed the lowest K value, total volatile basic nitrogen, free amino acids, total viable count, Pseudomonas spp., and H₂S-producing bacteria, which better maintain the quality of sea bass.

Radiosensitivity increase in FCV-F9 virus using combined treatments with natural antimicrobials and γ-irradiation

AIMS

The objective was to evaluate the possible synergistic effect of cranberry juice (CJ) and commercial citrus extract (BS) against FCV-F9 viral titre in vitro in combination with γ-irradiation and to determinate the D₁₀ values and radiosensitivity increase.

METHODS AND RESULTS

Virus samples were treated with a formulation containing a mixture of BS or CJ. Results showed a D₁₀ of 0·05, 0·42% and 1·34 kGy for the virus treated with the BS, the CJ and the irradiation alone respectively. Concentrations needed to reduce 6 log TCID₅₀  ml^-1 of viral titre were BS-0·3%, CJ-2·52% and 8·04 kGy. Irradiation combined with BS-0·01% and CJ-0·1% against FCV-F9 virus showed D₁₀ values of 0·74 and 0·72 kGy, respectively, resulting in a viral radiosensitization of 1·28 and 1·50 for respective treatments.

CONCLUSION

The higher viral radiosensitization observed after combining γ-irradiation with BS-0·01% and CJ-0·1% indicates that CJ and BS could be used as antiviral agents alone or in combination with γ-irradiation to prevent NoV outbreaks.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cranberry juice and BS could be used in hurdle approaches in combined treatment with γ-irradiation to assure food safety without a detrimental effect on nutritional value and maintain low processing cost.

Chitosan as a Wound Dressing Starting Material: Antimicrobial Properties and Mode of Action

Fighting bacterial resistance is one of the concerns in modern days, as antibiotics remain the main resource of bacterial control. Data shows that for every antibiotic developed, there is a microorganism that becomes resistant to it. Natural polymers, as the source of antibacterial agents, offer a new way to fight bacterial infection. The advantage over conventional synthetic antibiotics is that natural antimicrobial agents are biocompatible, non-toxic, and inexpensive. Chitosan is one of the natural polymers that represent a very promising source for the development of antimicrobial agents. In addition, chitosan is biodegradable, non-toxic, and most importantly, promotes wound healing, features that makes it suitable as a starting material for wound dressings. This paper reviews the antimicrobial properties of chitosan and describes the mechanisms of action toward microbial cells as well as the interactions with mammalian cells in terms of wound healing process. Finally, the applications of chitosan as a wound-dressing material are discussed along with the current status of chitosan-based wound dressings existing on the market.

Antimicrobial influence of nanoemulsified lemon essential oil and pure lemon essential oil on food-borne pathogens and fish spoilage bacteria

The antimicrobial activities of lemon oil based nanoemulsion and two different concentrations of lemon essential oil (100% and 10%) on food-brne pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Enterococcus faecalis and Salmonella Paratyphi A) and fish spoilage bacteria (Photobacterium damselae, Enterococcus faecalis, Vibrio vulnificus, Proteus mirabilis, Serratia liquefaciens, and Pseudomonas luteola) were compared in terms of disc diffusion, minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). The constitutes of extracted lemon essential oil were identified by using GC-MS. Viscosity, the mean droplet size, thermodynamic stability and refractive index of nanoemulsions were determined. The main components detected in the lemon essential oil were d-limonene, p-cymene, β-pinene with percentages of 52.85%, 14.36%, and 13.69%, respectively. It was found that lemon nanoemulsion was more effective on food-borne pathogens except K. pneumoniae than 100% lemon essential oil. 10% lemon essential oil showed the highest inhibition effect on S. Paratyphi A. The conversion of the essential oil into nanoemulsion improved antimicrobial activity. According to value of MIC, both nanoemulsion and 100% essential oil inhibited bacterial growth of all of the pathogen bacteria tested whereas they were less effective on inhibition of fish spoilage bacteria. However, 10% essential oil was more effective on spoilage bacteria than pathogens. MBC showed that nanoemulsion and 100% lemon essential oil presented a noticeable bactericidal activity against S. paratyphi A whereas 10% lemon essential oil was found as ≥25 mg/mL against pathogens and spoilage bacteria. Therefore, the use of nanoemulsion based on lemon essential oil can have potential as a natural antimicrobial agent against food-borne pathogen and spoilage bacteria for fish processing industry.

Ultrasound treatment to modified atmospheric packaged fresh-cut cucumber: Influence on microbial inhibition and storage quality

Influence of ultrasound treatment on microorganisms and the quality of modified atmospheric packaged fresh-cut cucumber during storage were investigated. Fresh-cut cucumber was treated with ultrasound (US, 20 kHz) in different time (5, 10 and 15 min) and then modified atmospheric packaged as well as stored at 4 °C for 15 d. The results showed that US treatment inhibited the growth of total number of colonies, mold and yeast in modified atmospheric packaged fresh-cut cucumber during storage. US treatment for 10 min effectively reduced the loss of weight, firmness, total soluble solids and total color change (ΔE), the increase of MDA content and the degradation of ascorbic acid content and flavor, as well as decreased water mobility and maintained cell wall integrity in fresh-cut cucumber during storage. Therefore, these results demonstrated that US treatment was helpful for inhibiting microorganisms and improving storage quality, and could be an effective method to enhance the preservative effect of modified atmospheric packaged fresh-cut cucumber.

Use of poly(ε-caprolactone)-based films for equilibrium-modified atmosphere packaging to extend the postharvest shelf life of garland chrysanthemum

A uniaxial-stretched poly(ε-caprolactone)/poly(propylene carbonate; PCL/PPC) composite film was prepared using a twin-screw extruder, and its utility as an equilibrium-modified atmosphere packaging (EMAP) film extending the shelf life of garland chrysanthemums stored at 2~4°C was explored. The oxygen, carbon dioxide, and water vapor penetration properties, mechanical properties, and gas permselectivity of PCL/PPC film used to package garland chrysanthemums were determined and compared to those of controlled low-density polyethylene (LDPE) and PCL films. Physicochemical properties such as package headspace gas composition, weight loss, leaf color, total chlorophyll content, ascorbic acid content, lipid peroxidation extent, and the sensory traits of garland chrysanthemums were investigated over a storage period of 14 days to compare the preservative effects of the various packages. PPC blending decreased the PCL gas and water vapor permeability and slightly increased the CO 2 permselectivity. These effects on gas and water vapor permeability, combined with the effects on gas permselectivity, enhanced preservation of packed garland chrysanthemums. Furthermore, an O2 inner atmosphere level of 2%~5%, and a CO 2 concentration not greater than 8%, was established by the PCL/PPC film in the absence of condensation. The results thus suggest that biodegradable film can be used as an EMAP film to better maintain the quality of freshly harvested garland chrysanthemums and to afford a longer shelf life during cold storage compared to LDPE film. Sensory evaluation indicated that the garland chrysanthemums were market-acceptable after 14 days of storage; LDPE-packed chrysanthemums were acceptable only up to 8 days of storage. The film thus improved storage life compared to that afforded by LDPE.

Chitosan-based (Nano)materials for Novel Biomedical Applications

Chitosan-based nanomaterials have attracted significant attention in the biomedical field because of their unique biodegradable, biocompatible, non-toxic, and antimicrobial nature. Multiple perspectives of the proposed antibacterial effect and mode of action of chitosan-based nanomaterials are reviewed. Chitosan is presented as an ideal biomaterial for antimicrobial wound dressings that can either be fabricated alone in its native form or upgraded and incorporated with antibiotics, metallic antimicrobial particles, natural compounds and extracts in order to increase the antimicrobial effect. Since chitosan and its derivatives can enhance drug permeability across the blood-brain barrier, they can be also used as effective brain drug delivery carriers. Some of the recent chitosan formulations for brain uptake of various drugs are presented. The use of chitosan and its derivatives in other biomedical applications is also briefly discussed.

Development of antimicrobial edible coating based on modified chitosan for the improvement of strawberries shelf life

Edible antimicrobial coating produced from chitosan (CS) and its derivative was applied to improve the shelf life of fresh strawberries at 10 °C. Fruits treated with coating solution was stored at 10 °C and evaluated for weight loss, visual decay and microbiological analysis. Results indicated that the percentage weight loss and the decay were significantly (p < 0.05) lower for chitosan-monomethyl fumaric acid (CS-MFA) than that of CS and control samples. The total aerobic count for CS-MFA was 3.32 log CFU/fruit and was considerably lowered (p < 0.05) than CS (3.83 log CFU/fruit) and control (5.31 log CFU/fruit) at the end of storage. Fruit coated with CS-MFA showed significantly lowered (p < 0.05) count of yeast and molds when compared with CS. In conclusion, the antimicrobial edible coating based on modified CS improved microbiological characteristics and increased the shelf life from 4 (control) to 8 days (coated fruits).

Photoinduced chitosan–PEG hydrogels with long-term antibacterial properties

The photo-induced synthesis of chitosan–PEG hydrogels with tremendous antibacterial and anti-adhesive properties even after 6 months’ storage.

Transcriptomic approach and membrane fatty acid analysis to study the response mechanisms of Escherichia coli to thyme essential oil, carvacrol, 2-(E)-hexanal and citral exposure

AIMS

The application of essential oils (EOs) and their components as food preservatives is promising but requires a deeper understanding of their mechanisms of action. This study aims to evaluate the effects of thyme EO, carvacrol, citral and 2-(E)-hexenal, on whole-genome gene expression (the transcriptome), as well as the fatty acid (FA) composition of the cell membranes of Escherichia coli K12.

METHODS AND RESULTS

Therefore, we studied the response against 1 h of exposure to sublethal concentrations of natural antimicrobials, of exponentially growing E. coli K12, using DNA microarray technology and a gas chromatographic method. The results show that treatment with a sublethal concentration of the antimicrobials strongly affects global gene expression in E. coli for all antimicrobials used. Major changes in the expression of genes involved in metabolic pathways as well as in FA biosynthesis and protection against oxidative stress were evidenced. Moreover, the sublethal treatments resulted in increased levels of unsaturated and cyclic FAs as well as an increase in the chain length compared to the controls.

CONCLUSIONS

The down-regulation of genes involved in aerobic metabolism indicates a shift from respiration to fermentative growth. Moreover, the results obtained suggest that the cytoplasmic membrane of E. coli is the major cellular target of EOs and their components. In addition, the key role of membrane unsaturated FAs in the response mechanisms of E. coli to natural antimicrobials has been confirmed in this study.

SIGNIFICANCE AND IMPACT OF THE STUDY

The transcriptomic data obtained signify a further step to understand the mechanisms of action of natural antimicrobials also when sublethal concentrations and short-term exposure. In addition, this research goes in deep correlating the transcriptomic modification with the changes in E. coli FA composition of cell membrane identified as the main target of the natural antimicrobials.