Anti-quorum sensing activity of spice oil nanoemulsions against food borne pathogens

Essential oil-nanoemulsion based edible coating: Innovative sustainable preservation method for fresh/fresh-cut fruits and vegetables

Utilizing plant-based sources for the preservation of fresh and fresh-cut fruits and vegetables offers a natural and chemical-free method. However, the inherent instability of plant bioactive compounds underscores the necessity for encapsulation techniques. Essential oil-based nanoemulsions (EO-NEs) stand out among food additives due to their distinctive antibacterial and antioxidant properties. This review delves into recent advancements in the application of EO-NEs as edible coatings for fresh and fresh-cut produce. It examines the efficacy of EO-NEs in enhancing the preservation of fruits and vegetables by harnessing their bioactive compounds for antibacterial, antifungal, and antioxidant activities. Additionally, the review accentuates the efficacy of EO-NEs in inhibiting biofilm formation on fruits and vegetables. It reveals that coatings derived from plant-source nanoemulsions exhibit exceptional mechanical, optical, and microstructural qualities, as well as superior water barrier properties. In contrast to conventional emulsions, nanocoatings facilitate the gradual and controlled release of antimicrobial and antioxidant compounds during food storage. This feature enhances bioactivity, extends shelf life, and enhances the nutritional profile of products. By preserving and protecting shelf stability, EO-NEs contribute to the maintenance of vegetable freshness. Nonetheless, ensuring their commercial viability necessitates additional research into the toxicity of EO-based nanoemulsions.

Effect of tragacanth gum-chitin nanofiber film containing free or nano-encapsulated cumin essential oil on the quality of chilled turkey burgers packed with oxygen absorber

This research was undertaken to assess the effect of tragacanth gum-chitin nanofiber (TG-CNF) film containing free (CEO) or encapsulated cumin essential oil (CNE) combined with oxygen absorber (OA) packaging on the shelf-life of ready-to-cook (RTC) turkey breast burgers during chilled storage. The experimental groups were OA and TG-CNF as single treatments, TG-CNF + CEO, TG-CNF + CNE, and TG-CNF + OA as binary treatments, TG-CNF + CEO + OA and TG-CNF + CNE + OA as ternary treatments, and control. The samples were stored at 3°C for 20 days and analyzed for microbial, physicochemical, and sensory attributes. Binary treatments, when compared to single treatments, and ternary treatments, when compared to binary treatments, exhibited enhanced effectiveness in managing microbial growth, hindering physicochemical alterations, and decelerating sensory alterations. At day 20, TG-CNF + CNE + OA group was identified as the most effective group in inhibiting the growth of total mesophilic bacteria (TMB), total psychrophilic bacteria (TSB), and coliforms (final counts were 4.8, 4.16, and ≤1 log CFU/g, respectively), and TG-CNF + CNE + OA and TG-CNF + CEO + OA groups were known as the most effective groups in inhibiting lactic acid bacteria (LAB) (final counts were 4.71 and 5.15 log CFU/g, respectively). Furthermore, the TG-CNF + CNE + OA treatment proved to be the most effective group in reducing the total volatile nitrogen (TVN) (final level was 19.2 mg N/100 g) and thiobarbituric acid reactive substances (TBARS) (final level was 0.119 mg malondialdehyde (MDA)/kg). TG-CNF + CNE + OA and TG-CNF + CEO + OA were the most efficient groups to delay the increasing rate of cooking loss (final values were 23.3% and 24.6%) and pH (final values were 7.01 and 6.99). The sample's shelf-life was 4 days in control and TG-CNF, 8 days in OA and TG-CNF + OA, 12 days in TG-CNF + CEO, 16 days in TG-CNF + CNE and TG-CNF + CEO + OA, and at least 20 days in TG-CNF + CNE + OA. As a result, the incorporation of TG-CNF + CNE alongside OA packaging emerges as a highly effective active packaging method for preserving RTC turkey breast burgers during chilled storage.

Comparison of the Efficiency of Selected Disinfectants against Planktonic and Biofilm Populations of Escherichia coli and Staphylococcus aureus

The aim of this study is to compare the efficacy of selected food disinfectants on planktonic populations of Staphylococcus aureus and Escherichia coli and on the same microorganisms (MOs) incorporated in a biofilm. Two disinfectants were used for treatment: peracetic acid-based disinfectant (P) and benzalkonium chloride-based disinfectant (D). Testing of their efficacy on the selected MO populations was performed using a quantitative suspension test. The standard colony counting procedure was used to determine their efficacy on bacterial suspensions in tryptone soy agar (TSA). The germicidal effect (GE) of the disinfectants was determined based on the decimal reduction ratio. For both MOs, 100% GE was achieved at the lowest concentration (0.1%) and after the shortest exposure time (5 min). Biofilm production was confirmed with a crystal violet test on microtitre plates. Both E. coli and S. aureus showed strong biofilm production at 25 °C with E. coli showing significantly higher adherence capacity. Both disinfectants show a significantly weaker GE on 48 h biofilms compared to the GE observed after application of the same concentrations on planktonic cells of the same MOs. Complete destruction of the viable cells of the biofilms was observed after 5 min of exposure to the highest concentration tested (2%) for both disinfectants and MOs tested. The anti-quorum sensing activity (anti-QS) of disinfectants P and D was determined via a qualitative disc diffusion method applied to the biosensor bacterial strain Chromobacterium violaceum CV026. The results obtained indicate that the disinfectants studied have no anti-QS effect. The inhibition zones around the disc therefore only represent their antimicrobial effect.

Assessment of Fennel Oil Microfluidized Nanoemulsions Stabilization by Advanced Performance Xanthan Gum

In this work, nanoemulsion-based delivery system was developed by encapsulation of fennel essential oil. A response surface methodology was used to study the influence of the processing conditions in order to obtain monomodal nanoemulsions of fennel essential oil using the microchannel homogenization technique. Results showed that it was possible to obtain nanoemulsions with very narrow monomodal distributions that were homogeneous over the whole observation period (three months) when the appropriate mechanical energy was supplied by microfluidization at 14 MPa and 12 passes. Once the optimal processing condition was established, nanoemulsions were formulated with advanced performance xanthan gum, which was used as both viscosity modifier and emulsion stabilizer. As a result, more desirable results with enhanced physical stability and rheological properties were obtained. From the study of mechanical spectra as a function of aging time, the stability of the nanoemulsions weak gels was confirmed. The mechanical spectra as a function of hydrocolloid concentration revealed that the rheological properties are marked by the biopolymer network and could be modulated depending on the amount of added gum. Therefore, this research supports the role of advanced performance xanthan gum as a stabilizer of microfluidized fennel oil-in-water nanoemulsions. In addition, the results of this research could be useful to design and formulate functional oil-in-water nanoemulsions with potential application in the food industry for the delivery of nutraceuticals and antimicrobials.

Effectiveness and mechanisms of essential oils for biofilm control on food-contact surfaces: An updated review

Microbial biofilms represent a constant source of contamination in the food industry, being also a real threat for human health. In fact, most of biofilm-producing bacteria are becoming resistant to sanitizers, thus arousing the interest in natural alternatives to prevent biofilm formation on foods and food-contact surfaces. In particular, studies on biofilm control by essential oils (EOs) application are increasing, being EOs characterized by unique mixtures of compounds able to impair the mechanisms of biofilm development. This review reports the anti-biofilm properties of EOs in bacterial biofilm control (inhibition, removal and prevention of biofilm dispersion) on food-contact surfaces. The relationship between EOs effect and composition, concentration, involved bacteria, and surfaces is discussed, and the possible sites of action are also elucidated. The findings prove the high biofilm controlling capability of EOs through the regulation of genes and proteins implicated in motility, Quorum Sensing and exopolysaccharides (EPS) matrix. Moreover, incorporation in nanosized delivery systems, formulation of blends and combination of EOs with other strategies can increase their anti-biofilm activity. This review provides an overview of the current knowledge of the EOs effectiveness in controlling bacterial biofilm on food-contact surfaces, providing valuable information for improving EOs use as sanitizers in food industries.

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 edible composite film based on chitosan and cumin essential oil-loaded nanoemulsion combined with low-dose gamma irradiation on microbiological safety and quality of beef loins during refrigerated storage

This research was conducted to assess the combined effect of chitosan (Ch) film containing cumin essential oil nanoemulsion (CNE) and low-dose gamma irradiation (GI) at 2.5 kGy on microbiological safety and quality of beef loins during 21 days of chilled storage. The growth of mesophilic and psychrophilic bacteria, Enterobacteriaceae, and lactic acid bacteria were retarded in all treated groups (Ch, GI, Ch + CNE, Ch + GI, and Ch + CNE + GI groups) compared to control group during storage time. The treatments also slowed down the increasing level of total volatile basic nitrogen and pH during storage, while irradiation increased the levels of thiobarbituric acid reactive substances and protein carbonyls in beef loins. All treatments except Ch were effective to control the growth of inoculated pathogenic bacteria, including Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella typhimurium, in loin samples. The combination of Ch + CNE + GI was the most effective treatment to control the population of microbial flora and inoculated pathogens, slow down some physicochemical changes, and enhance the storage life of beef loins. As a result, the combination of active chitosan film and low-dose gamma irradiation can ensure microbiological safety and is suggested for long time preservation of beef during chilled storage.

Antivirulence properties and related mechanisms of spice essential oils: A comprehensive review

In recent decades, reduced antimicrobial effectiveness, increased bacterial infection, and newly emerged microbial resistance have become global public issues, leading to an urgent need to find effective strategies to counteract these problems. Strategies targeting bacterial virulence factors rather than bacterial survival have attracted increasing interest, since the modulation of virulence factors may prevent the development of drug resistance in bacteria. Spices are promising natural sources of antivirulence compounds owing to their wide availability, diverse antivirulence phytochemical constituents, and generally favorable safety profiles. Essential oils are the predominant and most important antivirulence components of spices. This review addresses the recent efforts of using spice essential oils to inhibit main bacterial virulence traits, including the quorum sensing system, biofilm formation, motility, and toxin production, with an intensive discussion of related mechanisms. We hope that this review can provide a better understanding of the antivirulence properties of spice essential oils, which have the potential to be used as antibiotic alternatives by targeting bacterial virulence.

Nanoemulsion-loaded hydrogel coatings for inhibition of bacterial virulence and biofilm formation on solid surfaces

The indiscriminate use of antibiotics has led to the emergence of drug-resistant bacteria which has become one of the biggest challenges of the twenty-first century for the researchers to combat and in turn search for novel targets which could lead to the development of effective and sustainable therapies. Inhibition of biofilm formation and virulence of bacterial pathogens is an emerging approach to address the challenges related to bacterial infections. To suppress the virulence and biofilm formation by Escherichia coli O157:H7 (ECOH), we developed stable nanoemulsion (NE) of Gaultheria fragrantissima Wall. essential oil’s (EO) bioactive compounds, viz., eugenol (E-NE) and methyl salicylate (MS-NE) that showed significantly higher anti-biofilm and anti-virulence activities as compared to eugenol and methyl salicylate without affecting ECOH planktonic cell growth. Transcriptional analysis showed that E-NE and MS-NE reduced the expression of genes, including curli, type I fimbriae, Shiga-like toxins, quorum sensing, and ler-controlled toxins, which are needed for biofilm formation, pathogenicity, and attachment. E-NE and MS-NE loaded hydrogel coatings showed superior anti-biofilm activity against ECOH on glass, plastic and meat surfaces as compared to eugenol and methyl salicylate loaded coatings. Conclusively, NE-loaded hydrogel coatings could be used in combating ECOH infection on solid surfaces through anti-biofilm and anti-virulence strategies.

Preparation of Coaxial Polylactic Acid-Propyl Gallate Electrospun Fibers and the Effect of Their Coating on Salmon Slices during Chilled Storage

Pseudomonas fluorescens bacteria can grow well in cold-storage conditions and cause food spoilage. Quorum sensing (QS) is a biological pathway existing in a large number of microorganisms, through which bacteria regulate several of their physiological activities. A number of substances have been identified as quorum sensing inhibitors (QSIs); they can interfere with the QS system and control bacterial spoilage characteristics and production of virulence factors. In our previous study, propyl gallate at sub-minimum inhibitory concentration levels showed a potent anti-QS activity. Thus, in this study, coaxial polylactic acid-propyl gallate electrospun fibers were fabricated and their physicochemical properties were characterized. Salmon slices were coated with these electrospun fibers and the effect of this coating on the salmon slices during chilled storage was evaluated. The results showed that the electrospun fibers had a small diameter and smooth surface with no beads or other defects. The thermal stability, tensile strength, and other properties of the fibers were suitable for refrigerated storage conditions. Without inhibiting the bacterial growth in the salmon slices, the QSI-containing electrospun fibers exerted a significant inhibitory effect on the production of total volatile base nitrogen and trimethylamine. Furthermore, the deterioration of muscle tissue in the salmon slices was significantly delayed during cold storage. Quantitative analysis indicated that the electrospun fibers had a significant inhibitory effect on the bacterial spoilage ability. The results suggested that the electrospun fibers loaded with QSIs might be an effective strategy to control food spoilage and enhance the quality of aquatic food products.

Reducing Quorum Sensing-Mediated Virulence Factor Expression and Biofilm Formation in Hafnia alvei by Using the Potential Quorum Sensing Inhibitor L-Carvone

Quorum sensing (QS), one of the most remarkable microbiological discoveries, is considered a global gene regulatory mechanism for various traits in bacteria, including virulence and spoilage. Hafnia alvei, an opportunistic pathogen and a dominant psychrophile, uses the lux-type QS system to regulate the production of virulence factors and biofilms, which are harmful to the food industry. Based on the QS interference approach, this study aimed to reveal the efficacy of L-carvone at sublethal concentrations on QS-regulated virulence factors and biofilm formation in H. alvei. QS inhibitory activity was demonstrated by the reduction in swinging motility (61.49%), swarming motility (74.94%), biofilm formation (52.41%) and acyl-homoserine lactone (AHL) production (0.5 μL/mL). Additionally, in silico analysis and RT-qPCR studies for AHL synthase HalI and QS transcriptional regulator HalR revealed a plausible molecular mechanism for QS inhibition by L-carvone. These findings suggest that L-carvone (a main component of spearmint essential oils) could be used as a novel quorum sensing inhibitor to control H. alvei in the food industry.

Quorum sensing inhibitors as antipathogens: biotechnological applications

The mechanisms through which microbes communicate using signal molecules has inspired a great deal of research. Microbes use this exchange of information, known as quorum sensing (QS), to initiate and perpetuate infectious diseases in eukaryotic organisms, evading the eukaryotic defense system by multiplying and expressing their pathogenicity through QS regulation. The major issue to arise from such networks is increased bacterial resistance to antibiotics, resulting from QS-dependent mediation of the formation of biofilm, the induction of efflux pumps, and the production of antibiotics. QS inhibitors (QSIs) of diverse origins have been shown to act as potential antipathogens. In this review, we focus on the use of QSIs to counter diseases in humans as well as plants and animals of economic importance. We also discuss the challenges encountered in the potential applications of QSIs.

Factors impacting the interactions of engineered nanoparticles with bacterial cells and biofilms: Mechanistic insights and state of knowledge

Since their advent a few decades ago, engineered nanoparticles (ENPs) have been extensively used in consumer products and industrial applications and their use is expected to continue at the rate of thousands of tons per year in the next decade. The widespread use of ENPs poses a potential risk of large scale environmental proliferation of ENPs which can impact and endanger environmental health and safety. Recent studies have shown that microbial biofilms can serve as an important biotic component for partitioning and perhaps storage of ENPs released into aqueous systems. Considering that biofilms can be one of the major sinks for ENPs in the environment, and that the field of biofilms itself is only three to four decades old, there is a recent and growing body of literature investigating the ENP-biofilm interactions. While looking at biofilms, it is imperative to consider the interactions of ENPs with the planktonic microbial cells inhabiting the bulk systems in the vicinity of surface-attached biofilms. In this review article, we attempt to establish the state of current knowledge regarding the interactions of ENPs with bacterial cells and biofilms, identifying key governing factors and interaction mechanisms, as well as prominent knowledge gaps. Since the context of ENP-biofilm interactions can be multifarious-ranging from ecological systems to water and wastewater treatment to dental/medically relevant biofilms- and includes devising novel strategies for biofilm control, we believe this review will serve an interdisciplinary audience. Finally, the article also touches upon the future directions that the research in the ENP-microbial cells/biofilm interactions could take. Continued research in this area is important to not only enhance our scientific knowledge and arsenal for biofilm control, but to also support environmental health while reaping the benefits of the 'nanomaterial revolution'.

Essential oil based nanoemulsions to improve the microbial quality of minimally processed fruits and vegetables: A review

Due to the convenience and nutritional value, minimally processed fruits and vegetables (MPFV) are one of the rapid growing sectors in the food industry. However, their microbiological safety is a cause of great concern. Essential oils (EOs), known for potent antimicrobial efficacy have been shown to reduce microbial load in MPFV, but their low water solubility, high volatility and strong organoleptic properties limit their wide use. Encapsulating EOs to nanoemulsion offers a viable remedy for such limitations. Due to the unique properties of the EOs nanoemulsion, there has been an increasing interest in their fabrication and use in food system. The present review article encompasses the overview of the prominent microflora present in MPFV, the recent developments on the fabrication and stability of EOs based nanoemulsion, their in vitro antimicrobial activity and their application in MPFV. This review also discusses the EOs based nanoemulsions antimicrobial mechanism of action and their regulatory issues related to their use. Application of EOs based nanoemulsion either as washing disinfectant or with incorporation into edible coatings have been shown to considerably improve the microbial quality and safety of MPFV. This efficacy has been further shown to increase when combined with other hurdles. However, further studies are required on the toxicity of EOs based nanoemulsion to assure its commercial exploitation.

Quorum Quenching and Microbial Control through Phenolic Extract of Eugenia Uniflora Fruits

We describe the characterization of the centesimal composition, mineral and phenolic content of Eugenia uniflora fruit and the determination of the antioxidant, antimicrobial and quorum quenching activities of the pulp phenolic extract. Centesimal composition was determined according to standard methods; trace elements were measured by total reflection X-ray fluorescence spectroscopy. The phenolic compounds were extracted by solid-phase chromatography and quantified by spectrophotometry. Antioxidant activity was determined by using 3 different methods. Antimicrobial activity was evaluated against a panel of foodborne microorganisms and antiquorum sensing activity in Chromobacterium violaceum was performed by measuring inhibition of quorum sensing dependent violacein production. The centesimal composition (per 100 g of pulp) was as follows: protein 3.68 ± 0.21 g, lipids 0.02 ± 0.03 g, carbohydrates 10.31 g and fiber 2.06 g. Trace elements (mg/g of pulp) were determined as: K 0.90, Ca 3.36, Fe 0.60, Zn 0.17, Cl 0.56, Cr 0.06, Ni 0.04, and Cu 0.07. The pulp is a source of phenolic compounds and presents antioxidant activity similar to other berries. The fruit phenolic extract inhibited all tested bacteria. We also found that the fruit phenolic extract at low subinhibitory concentrations inhibited up to 96% of violacein production in C. violaceum, likely due to the fruit's phenolic content. This study shows the contribution of E. uniflora phenolic compounds to the antioxidant, antimicrobial and the newly discovered quorum quenching activity, all of which could be used by the food and pharmaceutical industries to develop new functional products.