Toxicological and metabolic investigations of the safety of N-α-Lauroyl-l-arginine ethyl ester monohydrochloride (LAE)

Lauric arginate ethyl ester: An update on the antimicrobial potential and application in the food systems

Lauric arginate ethyl ester (LAE), a cationic surfactant with low toxicity, displays excellent antimicrobial activity against a broad range of microorganisms. LAE has been approved as generally recognized as safe (GRAS) for widespread application in certain foods at a maximum concentration of 200 ppm. In this context, extensive research has been carried out on the application of LAE in food preservation for improving the microbiological safety and quality characteristics of various food products. This study aims to present a general review of recent research progress on the antimicrobial efficacy of LAE and its application in the food industry. It covers the physicochemical properties, antimicrobial efficacy of LAE, and the underlying mechanism of its action. This review also summarizes the application of LAE in various foods products as well as its influence on the nutritional and sensory properties of such foods. Additionally, the main factors influencing the antimicrobial efficacy of LAE are reviewed in this work, and combination strategies are provided to enhance the antimicrobial potency of LAE. Finally, the concluding remarks and possible recommendations for the future research are also presented in this review. In summary, LAE has the great potential application in the food industry. Overall, the present review intends to improve the application of LAE in food preservation.

Sustainable bio-based antimicrobials derived from fatty acids: Synthesis, safety, and efficacy

Some conventional sanitizers and antibiotics used in food industry may be of concerns due to generation of toxic byproducts, impact on the environment, and the emergence of antibiotic resistance bacteria. Bio-based antimicrobials can be an alternative to conventional sanitizers since they are produced from renewable resources, and the bacterial resistance to these compounds is of less concern than those of currently used antibiotics. Among the bio-based antimicrobial compounds, those produced via either fermentation or chemical synthesis by covalently or electrovalently attaching specific moieties to the fatty acid have drawn attention in recent years. Disaccharide, arginine, vitamin B1, and phenolics are linked to fatty acids resulting in the production of sophorolipid, lauric arginate ethyl ester, thiamin dilauryl sulfate, and phenolic branched-chain fatty acid, respectively, all of which are reported to exhibit antimicrobial activity by targeting the cell membrane of the bacteria. Also, studies that applied these compounds as food preservatives by combining them with other compounds or treatments have been reviewed regarding extending the shelf life and inactivating foodborne pathogens of foods and food products. In addition, the phenolic branched-chain fatty acids, which are relatively new compounds compared to the others, are highlighted in this review.

Hydrophobisation of Silica Nanoparticles Using Lauroyl Ethyl Arginate and Chitosan Mixtures to Induce the Foaming Process

We studied silica suspensions with chitosan and biodegradable synthetic surfactant lauroyl ethyl arginate (LAE). Hydrophilic and negatively charged silica nanoparticles were neutralised due to the coating with chitosan. That presence of LAE led to the partial hydrophobisation of their surface, which favoured their attachment to the surface of a thin foam film. It was found that the presence of small and medium-sized (6–9 nm) hydrophobic particles in the interfacial layer of lamella foam film inhibited the coalescence and coarsening processes, which prolonged the life of the foam. Furthermore, hydrophobising of 30 nm particles allowed the formation of large aggregates precipitating from the mixture under steady-state conditions. These aggregates, however, under the conditions of the dynamic froth flotation process in the foam column, were floated into the foam layer. As a result, they were trapped in the foam film and Plateau borders, effectively preventing liquid leakage out of the foam. These results demonstrate the efficiency of using chitosan-LAE mixtures to remove silica nanoparticles from aqueous phase by foaming and flotation.

Mechanism of fungal inhibition activity of Nα-lauroyl-L-arginine ethyl ester (LAE) and potential in control of Penicillium expansum on postharvest citrus 'Benimadonna' (Citrus reticulata × Citrus sinensis)

BACKGROUND

Citrus 'Benimadonna' (Citrus reticulata × Citrus sinensis) is a high-value perishable fruit; thus there is an urgent need for a preservation technology with high effectiveness and low safety risk from industries. Nα-Lauroyl-l-arginine ethyl ester hydrochloride (LAE) was applied to enhance preservability by compounding with natamycin, and a possible fungal inhibition mechanism based on the hypothesis of an impact on the cell membrane by surfactant was investigated.

RESULTS

In vitro testing showed that the minimum inhibitory concentration of LAE against Penicillium expansum (PE), isolated as the predominant spoilage-inducing fungus, was 32 mg L^-1 and it was partially synergistic with natamycin. Subsequent in vivo testing proved the inhibition capacity. During 90 days' refrigerated preservation, spoilage rate was significantly decreased by preharvest spraying versus control without extra taste loss, and LAE showed an alleviating benefit on total pectin loss. Subsequently, electron microscopic imaging and intracellular protein levels of PE exposed to LAE indicated that LAE stress led to increased permeability and decreased cell integrity. Moreover, peroxidase, superoxide dismutase and catalase revealed that LAE enhanced oxidative stress, while pectinase was antagonized.

CONCLUSION

The present investigation first introduced LAE as a candidate active ingredient for citrus preservative. A theoretical basis was provided for the development of preservation technology for high-value perishable fruit. According to the authors' knowledge this study is the first report on the inhibition mechanism of LAE in terms of oxidative stress. © 2022 Society of Chemical Industry.

Effects of Ethyl Lauroyl Arginate (LAE) on Biofilm Detachment: Shear Rate, Concentration, and Dosing Time

Biofilm formation is one of the main obstacles in membrane treatment. The non-oxidizing biocide ethyl lauroyl arginate (LAE) is promising for mitigating biofilm development on membrane surfaces. However, the operating conditions of LAE and their impact on biofilm detachment are not comprehensively understood. In this study, a real-time in vitro flow cell system was utilized to observe biofilm dispersal caused by the shear rate, concentration, and treatment time of LAE. This confirmed that the biofilm was significantly reduced to 68.2% at a shear rate of 3.42 s−1 due to the increased physical lifting force. LAE exhibited two different mechanisms for bacterial inactivation and biofilm dispersal. Biofilms treated with LAE at sub-growth inhibitory concentrations for a longer time could effectively detach the biofilm formed on the surface of the glass slides, which can be attributed to the increased motility of microorganisms. However, a high concentration (i.e., bactericidal concentration) of LAE should be seriously considered because of the inactivated sessile bacteria and their residual debris remaining on the surface. This study sheds light on the effect of LAE on biofilm detachment and provides insights into biofouling mitigation during the membrane process.

Microcystins can be extracted from Microcystis aeruginosa using amino acid-derived biosurfactants

Microcystin, a cyanotoxin produced by Microcystis aeruginosa growing in eutrophic waters, can promote liver tumors in people ingesting contaminated water. To date, water treatment systems have not been effective in removing or degrading these cyanotoxins. In this work, we investigated the inhibitory activity of surfactants on the growth of M. aeruginosa and their application to extract the intracellular produced cyanotoxins. The experiments involving growth inhibition and extraction of cyanotoxins were carried out using the non-biodegradable surfactant cetyl trimethyl ammonium bromide (CTAB) in addition to other biodegradable surfactants. These were Tween 80 and surfactants derived from amino acids and peptides, respectively, from arginine, SDA, and hydrolyzed peptone, SDP. We demonstrated that the tested surfactants could be used to inhibit the growth of M. aeruginosa. At this point, CTAB and SDA proved to be the most competent surfactants in reducing cyanobacterial growth. Moreover, microcystins have been successfully removed from the water employing a cloud point extraction protocol based on the use of these surfactants and ammonium sulfate.

Ethyl Lauroyl Arginate, an Inherently Multicomponent Surfactant System

Ethyl lauroyl arginate (LAE) is an amino acid-based cationic surfactant with low toxicity and antimicrobial activity. It is widely used as a food preservative and component for food packaging. When stored, LAE decomposes by hydrolysis into surface-active components Nα-lauroyl–l-arginine (LAS) or dodecanoic (lauric) acid. There are only a limited number of reports considering the mechanism of surface activity of LAE. Thus, we analysed the surface tension isotherm of LAE with analytical standard purity in relation to LAE after prolonged storage. We used quantum mechanical density functional theory (DFT) computations to determine the preferred hydrolysis path and discuss the possibility of forming highly surface-active heterodimers, LAE-dodecanoate anion, or LAE-LAS. Applying molecular dynamics simulations, we determined the stability of those dimers linked by electrostatic interactions and hydrogen bonds. We used the adsorption model of surfactant mixtures to successfully describe the experimental surface tension isotherms. The real part surface dilational modulus determined by the oscillation drop method follows a diffusional transport mechanism. However, the nonlinear response of the surface tension could be observed for LAE concentration close to and above Critical Micelle Concentration (CMC). Nonlinearity originates from the presence of micelles and the reorganisation of the interfacial layer.

Ethyl Lauroyl Arginate (LAE): Antimicrobial Activity of LAE-Coated Film for the Packaging of Raw Beef and Pork

In this study, the antimicrobial activity of an ethyl lauroyl arginate- (LAE®-) coated film applied to the packaging of raw beef and pork was evaluated. Two different trials were performed for each meat species, aiming to evaluate the functionality of the film in contrasting the development of the natural microflora and of a specific target agent, Escherichia coli ATCC 25922. In the first trial, LAE-coated packaging was applied to test its activity towards the natural meat microflora over a period of 24 days at 6-7°C. The comparison with the control sample series showed a slight initial inhibitory activity on total viable count, followed by a growing trend. In the second trial, the antimicrobial activity of the LAE-coated film was evaluated on raw beef and pork voluntarily inoculated with Escherichia coli: an initial killing effect on E. coli was detected in both pork and beef meat (reduction around 0.7 and 1 log CFU/g, respectively), followed by a stable trend for the following storage period (24 days).

The effect of lauric arginate on the thermal inactivation of starved Listeria monocytogenes in sous-vide cooked ground beef

The aim of this study was to examine the efficacy of lauric arginate (LAE, 1000 ppm - 3000 ppm) as an assisting tool to reduce starved Listeria monocytogenes population in ground beef following sous-vide processing at different temperatures (55-62.5 °C). Ground beef mixed with LAE was vacuum sealed and a laboratory water bath was used for sous-vide cooking. Loglinear and Weibull models were fit to the survival microbial population and the D and Z-values were determined at 55-62.5 °C. Calculated D-values ranged from 33.62 to 3.22 min at temperature 55-62.5 °C. LAE at higher concentration is an effective antimicrobial to increase the inactivation of the pathogen in sous-vide cooking. With the addition of LAE, D-values at 55 and 62.5 °C determined by the Loglinear model decreased from 31.86 to 2.28 min (LAE 1000 ppm) and 16.71 to 0.56 min (LAE 3000 ppm), respectively; whereas the D-values at 55 to 62.5 °C determined by the Weibull model were 44.26 and 2.09 min (LAE 1000 ppm) and 22.71 and 1.60 min (LAE 3000 ppm), respectively. This study shows that sous-vide processing of ground beef supplemented with higher concentration of LAE effectively inactivates L. monocytogenes and thus, helps increase the microbiological safety and product quality.

Ethyl-N-dodecanoyl-l-arginate hydrochloride combats pathogens with low-resistance generation by membrane attack and modifies gut microbiota structure

Ethyl-N-dodecanoyl-l-arginate hydrochloride (LAE, ethyl lauroyl arginate HCl) is a cationic surfactant used as a food preservative with broad-spectrum antibacterial activities. However, its resistance development, influences on gut microbiome and molecular target are unclear. In this study, bacteria were stimulated by LAE for 30 days to test the bacterial resistance. Several infected animal models were used to evaluate the antibacterial effect of LAE in vivo. Mice were orally treated with LAE to test its effect on animal growth. The influence of LAE on mice gut microbiome was analysed by 16S rDNA sequencing. The results indicated that Escherichia coli did not develop resistance to LAE. LAE significantly combats bacterial infection in mice, ducklings and piglets. Moreover, LAE promotes mouse weight gain without changing body composition or reducing animal vitality, and induces lower hepatotoxicity than ampicillin. In the mouse gut microbiome assessment and characterization, LAE modifies host gut microbiota structure. Mechanistically, LAE specifically binds to acidic phospholipids including phosphatidylserine, depolarizes the membrane and disrupts the bacterial membrane followed by bacterial growth inhibition. This study investigates the molecular mechanism of LAE as well as its antibacterial functions in poultry and livestock. Our data suggest LAE is a potential antibacterial agent in animal health.

Development of an Arginine Anchored Nanoglobule with Retrograde Trafficking Inhibitor (Retro-2) for the Treatment of an Enterohemorrhagic Escherichia coli Outbreak

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) or Shiga toxin-producing E. coli (STEC) is known to cause sporadic and epidemic gastrointestinal infections with several incidences of outbreaks. Antibiotic-based therapy further worsens the condition by facilitating the release of Shiga toxins (Stx) and lipopolysaccharides (LPS). Hence, there is an urgent need to develop an antibiotic-free, safe, and effective therapeutic intervention for the treatment of EHEC infections. We proposed a novel therapeutic strategy to address this clinical problem-kill, capture, and inhibit. We aimed to formulate and characterize lauroyl arginate ethyl ester (LAE) and Retro-2 loaded self-nano emulsifying drug delivery systems (SNEDDS). Retro-2 is a recently developed novel class of molecule, which can selectively inhibit retrograde transport of Stx. In this paper, we first carried out preformulation studies of Retro-2, followed by the development of SNEDDS forming arginine anchored nanoglobules (AR-NG), characterization of LPS binding to AR-NG, and finally evaluation of activity against EHEC. Retro-2 showed extremely poor solubility at all gastrointestinal pH values, susceptibility to acidic environments, and good permeability. The positively charged AR-NG spontaneously formed a globule size of 102.8 ± 1.9 nm with a surface charge of +52.15 ± 3 mV and increased the solubility of Retro-2. Further, binding and aggregation of LPS and AR-NG were confirmed by particle size, polydispersity index, zeta potential, fluorescent intensity, turbidity analysis, and a limulus amebocyte lysate (LAL) test. Additionally, a significant reduction in LPS induced TNF-α was observed in AR-NG treated macrophages. Thus, in this paper, we demonstrate a very promising and innovative therapeutic approach based on the "kill (E. Coli), capture (released LPS), and inhibit (transport of Stx)" concept.

Synergistic Antimicrobial Activity by Light or Thermal Treatment and Lauric Arginate: Membrane Damage and Oxidative Stress

The need for more effective antimicrobials is critical for the food industry to improve food safety and reduce spoilage of minimally processed foods. The present study was initiated to develop an efficient and novel antimicrobial approach which combines physical treatments (UV-A or mild heat) and generally recognized as safe lauroyl arginate ethyl (LAE) to inactivate surrogate strains, including Escherichia coli and Listeria innocua Synergistic inactivation of bacteria resulted in an ∼6-log reduction of target bacteria, while individual treatments resulted in <1.5-log inactivation under the same set of conditions. In addition, the synergistic mechanism between LAE and UV-A/mild heat was evaluated by supplementing with a variety of antioxidants for suppressing oxidative stress and measurement of cell membrane damage by nucleic acid release. These results demonstrate that the synergistic antimicrobial activity of LAE and mild physical stresses was suppressed by supplementation with antioxidants. The research also compared LAE with another membrane-targeting lipopeptide antimicrobial agent, polymyxin B, to understand the uniqueness of LAE-induced synergy. Briefly, differences in modes of action between LAE and polymyxin B were characterized by comparing the MIC, damage to liposomes, and oxidative stress generation. These differences in the mode of action between LAE and polymyxin B suggested that both compounds target cell membrane but significantly differ in mechanisms, including membrane disruption and oxidative stress generation. Overall, this study illustrates synergistic antimicrobial activity of LAE with light or mild heat and indicates a novel oxidative stress pathway that enhances the activity of LAE beyond membrane damage.IMPORTANCE This study highlights an effective antimicrobial processing approach using a novel combination of lauroyl arginate ethyl (LAE) and two different physical treatments, light (UV-A) and mild heat. Both combinations demonstrated synergistic inactivation against a model Gram-negative bacterium or a Gram-positive bacterium or both by a >5-log reduction. Further mechanistic study revealed that oxidative stress is responsible for synergistic inactivation between LAE and UV-A, while both membrane damage and oxidative stress are responsible for the synergistic combination between LAE and mild heat. The mode of action of LAE was further compared to that of polymyxin B and analyzed using artificial membrane model systems and the addition of antioxidants. The proposed combination of LAE and common physical treatments may improve food preservation, food safety, and current sanitation processes for the food industry and the inactivation of pathogenic strains in biomedical environments.

Mechanisms of Nα-lauroyl arginate ethyl ester against Penicillium digitatum and Pectobacterium carotovorum subsp. carotovorum

The purpose of this study was to investigate the antimicrobial activity and mechanisms of Nα-lauroyl arginate ethyl ester (LAE) against Penicillium digitatum and Pectobacterium carotovorum subsp. carotovorum. The minim inhibitory concentrations of LAE against P. digitatum and P. carotovorum were found to be 400 and 25 μg/ml, respectively. Loss of intracellular protein and nucleic acid increased significantly, and membrane permeability reached 76.28, 54.29 and 85.20%, respectively, when 400 μg/ml of LAE was applied to the hyphae and spores of P. digitatum and to P. carotovorum. Flow cytometry showed that LAE reduced the membrane potential, and the depolarization ratios of P. digitatum and P. carotovorum were 98.19 and 97.25% (P < 0.05), respectively. Transmission electron microscopy photos revealed that LAE caused a rough surface, irregular cellular organelles, protoplast shrinkage, intracytoplasmic coagulation and empty cavities in all three cell types. These results showed that LAE had notable ability to damage the structure of fungal and bacterial cells, making it a possible alternative chemical for use in the preservation of fruits and vegetables.

Antibacterial Films Made of Ionic Complexes of Poly(γ-glutamic acid) and Ethyl Lauroyl Arginate

The biocide agent LAE (ethyl ^αN-lauroyl l-arginate chloride) was coupled with poly(γ-glutamic acid) (PGGA) to form stable ionic complexes with LAE:PGGA ratios of 1 and 0.5. The nanostructure adopted by these complexes and its response to thermal changes were examined in detail by Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) using synchrotron radiation in real time. A layered biphasic structure with LAE filling the space between the polypeptidic sheets was adopted in these complexes. The complexes were stable up to above 250 °C, non-water soluble, and were able to form consistent transparent films. The release of LAE from the complexes upon incubation in aqueous buffer was examined and found to depend on both pH and complex composition. The antibacterial activity of films made of these complexes against Gram-positive (L. monocytogenes and S. aureus) and Gram-negative (E. coli and S. enterica) bacteria was preliminary evaluated and was found to be very high against the formers and only moderate against the later. The bactericide activity displayed by the LAE·PGGA complexes was directly related with the amount of LAE that was released from the film to the environment.

Antimicrobial edible coatings and films from micro-emulsions and their food applications

This study focused on the use of antimicrobial edible coatings and films from micro-emulsions to reduce populations of foodborne pathogens in foods. Corn-Bio-fiber gum (C-BFG) was used as an emulsifier with chitosan. Allyl isothiocyanate (AIT) and lauric arginate ester (LAE) served as antimicrobials. Micro-emulsions were obtained from a solution consisting of 1% chitosan, 0.5% C-BFG, and 1-4% AIT or LAE which was subject to high pressure homogenization (HPH) processing at 138MPa for 3cycles. Coatings and films produced from the micro-emulsions had micro-pores with sizes ranging from 100 to 300nm and micro-channels that hold antimicrobials effectively and facilitate the release of antimicrobials from the center to the surface of the films or coatings, thus enhancing their antimicrobial efficacy. The coatings and films with 1% AIT reduced populations of Listeria innocua by over 5, 2, and 3 log CFU in culture medium (Tryptic soy broth, TSB), ready-to-eat meat, and strawberries, respectively. The coatings and films with 1% LAE reduced populations of Escherichia coli O157:H7 and Salmonella spp. by over 5 and 2 log CFU in TSB and strawberries, respectively. This study provides an innovative approach for the development of effective antimicrobial materials to reduce food borne pathogenic contaminants on ready-to-eat meat, strawberries, or other food.

Lauroyl Arginate Ethyl Blocks the Iron Signals Necessary for Pseudomonas aeruginosa Biofilm Development

Pseudomonas aeruginosa is a ubiquitous gram-negative bacterium capable of forming a biofilm on living and non-living surfaces, which frequently leads to undesirable consequences. We found that lauroyl arginate ethyl (LAE), a synthetic non-oxidizing biocide, inhibited biofilm formation by P. aeruginosa at a sub-growth inhibitory concentration under both static and flow conditions. A global transcriptome analysis was conducted using a gene chip microarray to identify the genes targeted by LAE. In response to LAE treatment, P. aeruginosa cells up-regulated iron acquisition and signaling genes and down-regulated iron storage genes. LAE demonstrated the capacity to chelate iron in an experiment in which free LAE molecules were measured by increasing the ratio of iron to LAE. Furthermore, compared to untreated cells, P. aeruginosa cells treated with LAE exhibited enhanced twitching motility, a phenotype that is usually evident when the cells are starved for iron. Taken together, these results imply that LAE generated iron-limiting conditions, and in turn, blocked iron signals necessary for P. aeruginosa biofilm development. As destroying or blocking signals leading to biofilm development would be an efficient way to mitigate problematic biofilms, our findings suggest that LAE can aid in reducing P. aeruginosa biofilms for therapeutic and industrial purposes.

Stearylated cycloarginine nanosystems for intracellular delivery – simulations, formulation and proof of concept

Novel cationic agent liposomes performed better in silico translating in higher cellular uptake with reduced toxicity.

Antimicrobial Activity of Cinnamaldehyde, Carvacrol, and Lauric Arginate against Salmonella Tennessee in a Glycerol-Sucrose Model and Peanut Paste at Different Fat Concentrations

The objective of this study was to investigate the antimicrobial activities of carvacrol, cinnamaldehyde, and lauric arginate (LAE) against Salmonella in a low water activity (aw ) glycerol-sucrose model and in peanut paste with different fat concentrations. Salmonella Tennessee was inoculated into the model and the low fat (<5%) and high fat (50%) peanut paste adjusted to aw 1.0, 0.7, 0.5, and 0.3 and with or without cinnamaldehyde, carvacrol, or LAE. The survival of the bacterium over 3 or 5 days at 25°C was evaluated. Reduced aw alone decreased the viable population over time, with the highest reduction at the lowest aw. In the glycerol-sucrose model, all antimicrobial agents significantly reduced the population over time (P < 0.05) compared with the controls. LAE was more lethal than the essential oil components, reducing the population to undetectable levels by day 2 for all aw. Cinnamaldehyde was more effective than carvacrol at aw 0.5 and 0.3 (2.7- to 2.9-log versus 0.39- to 1.97-log reductions on day 3). In low-fat peanut paste, none of the antimicrobial agents inhibited growth of the pathogen at aw 1.0. However, inactivation was enhanced at reduced aw. Cinnamaldehyde and LAE both reduced the pathogen population to undetectable levels on day 5 at the highest concentration tested (ca. 10 times higher than that in the glycerol-sucrose model). Inactivation efficacy of all antimicrobial agents was greatly decreased but not eliminated in 50% fat peanut paste. Results suggest that the test antimicrobial agents were effective under low aw conditions, but significantly higher concentrations are needed for potential food applications, and fat concentration can negatively impact the efficacy of these antimicrobial agents.

Enhanced inactivation of food-borne pathogens in ready-to-eat sliced ham by near-infrared heating combined with UV-C irradiation and mechanism of the synergistic bactericidal action

The objective of the study described in this article was, first, to investigate the effect of the simultaneous application of near-infrared (NIR) heating and UV irradiation on inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in ready-to-eat (RTE) sliced ham and as well as its effect on product quality and, second, to elucidate the underlying mechanisms of the synergistic bactericidal action of NIR heating and UV irradiation. With the inoculation amounts used, simultaneous NIR-UV combined treatment for 70 s achieved 3.62, 4.17, and 3.43 log CFU reductions of E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively. For all three pathogens, the simultaneous application of both technologies resulted in an additional log unit reduction as a result of their synergism compared to the sum of the reductions obtained after the individual treatments. To investigate the mechanisms of NIR-UV synergistic injury for a particular microorganism in a food base, we evaluated the effect of four types of metabolic inhibitors using the overlay method and confirmed that damage to cellular membranes and the inability of cells to repair these structures due to ribosomal damage were the primary factors related to the synergistic lethal effect. Additionally, NIR-UV combined treatment for a maximum of 70 s did not alter the color values or texture parameters of ham slices significantly (P > 0.05). These results suggest that a NIR-UV combined process could be an innovative antimicrobial intervention for RTE meat products.

Electrostatic interactions of cationic lauric arginate with anionic polysaccharides affect antimicrobial activity against spoilage yeasts

AIMS

To investigate the effect of anionic polysaccharides often used in beverage applications (xanthan and λ-carrageenan) on the antimicrobial efficacy of the cationic surfactant lauric arginate (LAE) against typical spoilage yeasts.

METHODS AND RESULTS

The antimicrobial efficacy of LAE against Saccharomyces cerevisiae, Candida albicans and Zygosaccharomyces bailii in the absence and presence of anionic polysaccharides was assessed by microtitre and macrobroth dilution assays. Combining LAE with either xanthan or λ-carrageenan caused a pronounced decrease in LAE's antimicrobial efficacy, with the minimal inhibitory and lethal concentrations (MIC and MLC) both increasing with increasing polysaccharide concentration. This reduction in antimicrobial efficacy was more pronounced for the addition of λ-carrageenan. To determine the cause of loss of activity, physical properties of solutions were examined. Turbidity and sedimentation measurements indicated that complexes between LAE and anionic polysaccharides had been formed. Electrophoresis measurements showed that complexes had varying electrical charges and dimensions depending on solution composition.

CONCLUSION

Results suggest that electrostatic interactions between LAE and anionic polysaccharides play a major role in complex formation and loss of antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results have important implications for the utilization of LAE as an antimicrobial agent in beverage and food products containing anionic polysaccharides.

Development of a novel antimicrobial film based on chitosan with LAE (ethyl-N(α)-dodecanoyl-l-arginate) and its application to fresh chicken

Chitosan (CS) films incorporating the antimicrobial compound ethyl-N(α)-dodecanoyl-l-arginate (LAE) were developed for food packaging applications. Cast chitosan films were made with 1, 5 or 10% LAE and 20% glycerol in the film forming solution. Optical properties, release of LAE and antimicrobial activity of developed films was determined. The minimum inhibitory concentration (MIC) and the minimum biocide concentration (MBC) of LAE were determined. CS films with LAE were transparent and uniform, without discontinuities or visible particles and no visual differences could be perceived between CS and CS-LAE films. When in contact with an aqueous food simulant, the agent was fully released following a Fickian behavior in a few hours at 4 and 28°C. Antimicrobial activity of films against mesophiles, psychrophiles, Pseudomonas spp., colifoms, lactic acid bacteria, hydrogen sulfide-producing bacteria, yeast and fungi, was evaluated at two, six and eight days for its application on chicken breast fillets. Films were active against bacteria, yeasts and fungi in liquid and solid media. CS films evidenced antimicrobial activity in the range 0.47-2.96 log reductions, while CS-5%LAE film produced 1.78-5.81 log reduction. Results highlighted that LAE incorporation in a chitosan-based packaging structure may provide a relevant antimicrobial activity that could improve the stability of fresh poultry products.

Efficacy of ε-polylysine, lauric arginate, or acidic calcium sulfate applied sequentially for Salmonella reduction on membrane filters and chicken carcasses

Salmonella contamination continues to be one of the major concerns for the microbiological safety of raw poultry products. Application of more than one decontamination agent as a multihurdle intervention to carcasses in a processing line might produce greater reductions than one treatment alone due to different modes of action of individual antimicrobials. In this study, all possible two-way combinations and individual applications of ε-polylysine (EPL), lauric arginate (LAE), and acidic calcium sulfate (ACS) solutions were evaluated for their effects against Salmonella enterica serovars, including Enteritidis and Typhimurium, using a sterile membrane filter model system. The combinations that provided higher Salmonella reductions were further evaluated on inoculated chicken carcasses in various concentrations applied in a sequential manner. Sequential spray applications of 300 mg of EPL per liter followed by 30% ACS and of 200 mg of LAE per liter followed by 30% ACS produced the highest Salmonella reductions on inoculated chicken carcasses, by 2.1 and 2.2 log CFU/ml, respectively. Our results indicated that these sequential spray applications of decontamination agents are effective for decreasing Salmonella contamination on poultry carcasses, but further studies are needed to determine the effectiveness of these combinations over a storage period.

Formation and stabilization of antimicrobial delivery systems based on electrostatic complexes of cationic-non-ionic mixed micelles and anionic polysaccharides

Lauric arginate (LAE) is a cationic surfactant that is of great interest to the food industry because of its strong antimicrobial activity. However, its application within foods and beverages is currently restricted because of its limited solubility in aqueous solutions and its bitter taste, which have been associated with its cationic nature. This study examines whether electrostatic complexes between cationic LAE mixed micelles and anionic polysaccharides could be used to improve LAE functionality. Two types of pectin (high and low methoxyl) were titrated into buffer solutions containing either LAE micelles or LAE/Tween 20 mixed micelles (pH 3.5, 50 mM citrate buffer). The electrical characteristics of the micelles or micelle/pectin complexes were assessed by microelectrophoresis measurements, while their stability to aggregation was evaluated by light scattering measurements. LAE micelle/pectin complexes formed large aggregates that rapidly sedimented. On the other hand, mixed micelle/pectin complexes (1:1 LAE/Tween 20, w/w) were stable to aggregation and formed clear solutions. The electrical charge of mixed micelles changed from +8 to -15 mV when the pectin concentration was increased (0.00-0.05 wt %), indicating an electrostatic interaction between anionic pectin molecules and cationic micelles. Lower concentrations of low methoxyl pectin were required (0.01 wt %) to change the net charge of mixed micelles from positive to negative than high methoxyl pectin (0.025 wt %). Our results suggest that the addition of pectin to mixed LAE/Tween 20 micelles leads to the formation of electrostatic complexes that may be useful as functional ingredients in food and other products.