Antimicrobial Agents In Food Research Articles

Unlocking the Therapeutic and Antimicrobial Potential of Prunus armeniaca L. Seed Kernel Oil.

The Prunus armeniaca L. (bitter apricot) is an apricot fruit tree categorized on the basis of the bitter taste of its seed kernel. In this study, the functional, medicinal, and therapeutic potential of bitter apricot seed kernel oil (BASKO) was evaluated. The qualitative screening of BASKO was performed using standard methodologies. The chemical profile of the oil was analyzed with the help of Fourier transform infrared (FTIR) and gas chromatography and mass spectrometry (GC-MS). Results revealed the presence of different phytochemical constituents comprising steroids, flavonoids, terpenoids, alkaloids, and cardiac glycosides. The antioxidant activity of the oil was determined by a 2,2,diphenyl-1picrylhydrazyl (DPPH) radical inhibition essay. Total phenolic and flavonoid contents were 10.6 ± 1.32 mg GAE/g and 4.75 ± 0.11 mg QE/g, respectively. DPPH inhibition of 89.5% was achieved at 1000 μg/mL of BASKO, with IC50 = 90.44 μg/mL (83.47-96.67 μg/mL with 95% CI). The antimicrobial potential of the BASKO revealed the inhibition of Escherichia coli (20.3 ± 2.08 mm), Salmonella typhi (19.3 ± 2.51 mm), Klebsiella pneumoniae (16.6 ± 1.52 mm), Pseudomonas aeruginosa (17 ± 2 mm), and Staphylococcus aureus (25 ± 1.01 mm). The minimum inhibitory concentration (MIC) value was 250 μL/mL for K. pneumoniae, S. typhi, P. aeruginosa, and S. aureus, whereas 62.5 μL/mL for E. coli. Moreover, BASKO showed antifungal potential against Trichophyton tonsurans (77.3 ± 2.08%), Epidermophyton floccosum (69.6 ± 3.51%), Aspergillus niger (74.3 ± 2.56%), Aspergillus flavus (90 ± 3%), and Mucor mucedo (78.3 ± 2.51%). Antileishmanial activity of oil was evaluated against Leishmania major by MTT assay, and an IC50 value of 89.75 μg/mL was observed. The study revealed that BASKO is a good source of biologically active compounds to be used as functional, therapeutical, and antimicrobial agents in food and pharmaceutical products.

A review on mannosylerythritol lipids and their properties, applications and roles in the circular economy

AbstractMannosylerythritol lipid (MEL) is a microbial surface‐active glycolipid biosurfactant produced by numerous microorganisms. MEL is produced as a major product by Pseudozyma sp. and as a minor product by Ustilago sp. MEL has recently received much practical attention due to its structural diversity, broad biochemical functions, and biocompatibility with the environment. In this review, the production of MEL from various feedstocks, and antimicrobial and antiadhesive properties are discussed. Furthermore, the applications of MEL as an antimicrobial agent in food, moisturizer in cosmetics, as an apoptotic agent in pharmaceuticals, and as a wetting agent in agriculture applications are highlighted. Finally, an overview of MEL production from waste materials presents huge potential for increasing the necessary change to a circular economy.

Sunflower meal ethanol solute powder as an upcycled value-product to prolong food shelf life

In this study the potential of sunflower meal ethanol-wash powder (SEWP) to be used as antimicrobial agent in liquid foods was investigated. SEWP represents the waste of the main process of protein isolation from industrially produced sunflower meal. The washing liquids remaining after treatment of the sunflower meal with 75% aqueous ethanol solution were collected and turned into powder rich in bioactive compounds. Due to its recognized properties, different concentrations (2.5 and 5% w/v) of SEWP were first tested in vitro against Alicyclobacillus acidoterrestris and a cocktail of Pseudomonas putida and Pseudomonas fluorescens strains, using appropriate culture media. Then, the SEWP antimicrobial efficacy was tested on two real food matrices differing in their composition. Soymilk, rich in proteins, and apple juice, composed mainly of carbohydrates, were used as food models. Concentrations equal to 1%, 1.5%, 2%, 2.5%, 5% and 7.5% (w/v) SEWP were tested in the juice, whereas the sole three highest concentrations were tested in the soymilk. Both beverages were pre-inoculated with different spoilage bacteria. The same mix of Pseudomonas spp. and A. acidoterrestris strain used for the in vitro test were employed to contaminate the soymilk and the apple juice, respectively. In vitro results showed moderate effects of SEWP against selected target microorganisms. On the contrary, two completely different microbial evolutions were recorded in the soymilk and apple juice. The three concentrations of SEWP were slightly effective against spoilage of soymilk, whereas all the concentrations used in the juice were sufficient to completely inhibit microbial growth of A. acidoterrestris. The shelf life of the apple juice supplemented with 1% SEWP was extended for more than 21 days. Considering both the antimicrobial efficacy and the sensory properties of the juice, the lowest SEWP concentration (1% w/v) demonstrated the best result as a bioprotectant. Overall results imply dependence of SEWP antimicrobial efficiency on food composition and a need of preliminary evaluation of the product if used as an antimicrobial agent in the food industry.

Isolation of Bacterial Pathogens Associated with Commercially Available Spices in Mangaluru City, India

Spices are important sources of natural flavouring, colouring and antimicrobial agents in food and medicine. In India, spices are widely produced, consumed and exported across the world. Like many other agricultural commodities, spices are exposed to a wide range of bacterial contamination during their harvesting, processing and transportation causing foodborne illnesses. Spices in their desiccated form offer an environment conducive to the survival of many pathogenic bacteria which becomes challenging for spice manufacturers to control or mitigate any bacterial contamination. The present study aimed at the isolation, phenotypic and genotypic identification of bacterial pathogens namely Salmonella spp., Bacillus cereus, Staphylococcus aureus and Escherichia coli associated with spices collected in and around Mangaluru, Karnataka. Isolation of bacterial pathogens was performed using a modified standard FDA BAM methodology. A total of 140 spice samples inclusive of pepper, clove, cumin, red chillies, turmeric, coriander, clove and fennel in whole and powdered form were screened for pathogens. No targeted bacterial pathogens were present in the samples collected. It can be inferred that good agricultural, manufacturing and hygienic practices were maintained in the commercial supply of spices. The absence of bacteria could also be attributed to the inherent antimicrobial properties of spices.

Cationic Chitooligosaccharide Derivatives Bearing Pyridinium and Trialkyl Ammonium: Preparation, Characterization and Antimicrobial Activities.

In this study, chitooligosaccharide-niacin acid conjugate was designed and synthesized through the reaction of chitooligosaccharide and nicotinic acid with the aid of N,N'-carbonyldiimidazole. Its cationic derivatives were prepared by the further nucleophilic substitution reaction between the chitooligosaccharide-niacin acid conjugate and bromopropyl trialkyl ammonium bromide with different alkyl chain lengths. The specific structural characterization of all derivatives was identified using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR), and the degree of substitution was obtained using the integral area ratio of the hydrogen signals. Specifically, the antibacterial activities against Escherichia coli, Staphylococcus aureus, Pseudoalteromonas citrea and Vibrio harveyi were evaluated using broth dilution methods. In addition, their antifungal activities, including Botrytis cinerea, Glomerella cingulate and Fusarium oxysporum f. sp. cubense were assayed in vitro using the mycelium growth rate method. Experimental data proved that the samples showed antibacterial activity against four pathogenic bacteria (MIC = 1-0.125 mg/mL, MBC = 8-0.5 mg/mL) and enhanced antifungal activity (50.30-68.48% at 1.0 mg/mL) against Botrytis cinerea. In particular, of all chitooligosaccharide derivatives, the chitooligosaccharide derivative containing pyridinium and tri-n-butylamine showed the strongest antibacterial capacity against all of the test pathogenic bacteria; the MIC against Vibrio harveyi was 0.125 mg/mL and the MBC was 1 mg/mL. The experimental results above showed that the introduction of pyridinium salt and quaternary ammonium salt bearing trialkyl enhanced the antimicrobial activity. In addition, the cytotoxicity against L929 cells of the chitooligosaccharide derivatives was evaluated, and the compounds exhibited slight cytotoxicity. Specifically, the cell viability was greater than 91.80% at all test concentrations. The results suggested that the cationic chitooligosaccharide derivatives bearing pyridinium and trialkyl ammonium possessed better antimicrobial activity than pure chitooligosaccharide, indicating their potential as antimicrobial agents in food, medicine, cosmetics and other fields.

Simultaneous preparation of water- and lipid-soluble antioxidant and antibacterial activity of purified carnosic acid from Rosmarinus offoccnalis L.

Rosemary is an widely used plant in processed foods and cosmetics due to its high antioxidant activity and fascinating flavor. However, complicated production processes and high price of rosemary antioxidant place restrictions on its commercial application. In this research, a simple, highly efficient procedure for simultaneous preparation of water- and lipid-soluble rosemary extracts was developed. Rosemary leaves were macerated with 1 minimum volume (MV) of 70 % acidic ethanol-water solution for 3 h. Next, column chromatographic extraction method (CCE) designed in our laboratory was employed for simultaneous extraction of carnosic acid and rosmarinic acid, and their extraction rates were 96 % and 94 %, respectively. After the removal of ethanol, the supernatant and precipitate were separately collected as water-soluble extract containing 6.84 % rosmarinic acid and lipid-soluble extract containing 31.18 % carnosic acid. Then, the lipid-soluble extract was separated through dissolution with n-hexane, liquid–liquid extraction with NaHCO3, and precipitation at a pH of 1.0; this yielded a carnosic acid product with 90 % purity. After crystallization with cyclohexane, carnosic acid with > 98 % purity was obtained. The prepared carnosic acid could effectively suppress the growth of Gram-positive bacteria and Edwardsiella tarda growth. This study made complete use of rosemary resources, greatly reducing rosemary extract preparation and carnosic acid extraction costs. Further investigation of the antibacterial effectiveness of carnosic acid could promote its industrial applications as antimicrobial agent in food and aquaculture.

Chemically Characterized Essential Oils of Citrus reticulata and Thymus vulgaris L. and Their Nanoemulsions Inhibited the Pathogenic Microbes Causing Mastitis in Cattle

Essential oils (EOs) of Citrus reticulata (C. reticulata, mandarin) peels and Thymus vulgaris (T. vulgaris) are well known active microbial inhibitors. Nanoemulsion preparation is a modern technique for enhancing antimicrobial potentialities. EOs of both plants were prepared and chemically characterized using gas chromatography/mass spectrometry. Methyl-N-methyl anthranilate (non terpenoidal compound) and monoterpene hydrocarbons are the main components of mandarin peels EO with relative concentrations of 61.07% and 35.15%, respectively. Whereas, T. vulgaris was characterized by abundance of oxygenated monoterpenes and monoterpene hydrocarbons with relative concentrations of 66.89%, and 25.74%, respectively. The antimicrobial potentialities of EOs and their nanoemulsions were assayed. Mandarin EO exhibited strong activities against Citrobacter diversus (ATCC 13315), Proteus vulgaris (ATCC 13315), and Escherichia coli (resis.) with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 12.5 and 25 μg mL−1, respectively. On the other hand, mandarin nanoemulsion showed potentialities against all strains with MIC and MBC of 3.13 and 6.25 μg mL−1, respectively. T. vulgaris EO showed antibacterial potentialities against C. diversus, P. vulgaris, Staphylococcus aureus, and E. coli (resis.) with MIC of 0.19 μg mL−1 and a moderate activity against the other strains. Also, its nanoemulsion exhibited better growth inhibition against C. diversus, P. vulgaris, and E. coli (resis.) at 0.19 μg mL−1. Mandarin EO possessed significant antifungal activities against Candida albicans, Candida tropicalis, and Candida glabrata with MIC of 0.19, 0.78, and 1.56 μg mL−1, respectively. The mandarin nanoemulsion had a significant activity against C. glabrata and C. tropicalis with MIC of 0.39 and 1.56 μg mL−1, respectively. T. vulgaris EO and its nanoemulsion are significant antifungals for all strains with MIC of 0.19 and 0.39 μg mL−1, respectively. The findings deduced the significant role of EOs of both plants and their nanoformulations as antimicrobial agents in food and pharmaceutical industries.

Preliminary investigations on antimicrobial, antioxidant and nutritional properties of freshwater snail Brotia costula (Rafinesque, 1833)

The present study aimed to evaluate the bioactive properties of freshwater snail Brotia costula (Rafinesque, 1833) meat along with its nutritional and functional properties. The soft tissue of B. costula had excellent nutritional properties as reflected in the high protein (13.83%), carbohydrate (10.70%) and polyunsaturated fattyacid (PUFA) content (37.7% of total fatty acid) of the meat. Among protein fractions, the major fraction was myofibrillar (51.40%) followed by sarcoplasmic (23.86%), stroma (17.89%) and alkali-soluble protein fractions (11.67%), whilst high non-protein nitrogen (27.23%) was also observed. To assess the bioactive properties, snail meat was extracted in three different solvents viz. 100% ethanol (l00EE), 50% ethanol (50EE) and 100% water (10WE). Among the three solvent extracts, 100% ethanol extract (100EE) showed excellent antioxidative properties as confirmed by four different antioxidant assays. The FTIR spectral analysis revealed strong absorbance for functional groups (phenol and carbonyl) in 100 EE tissue extract. The 100 EE showed maximum inhibition against spoilage bacteria (Pseudomonas putida, 21.3 mm) than pathogenic bacteria (Escherichia coli, 11.6 mm). Overall, it can be concluded that B. costula may be used as a good nutritional source and a potent natural antioxidant and antimicrobial agent in food and feed preparations. Keyword: Antioxidant activity, Antibacterial activity, Cholesterol, Freshwater snail, FTIR

Antimicrobial peptides (AMPs): A promising class of antimicrobial compounds.

Antimicrobial peptides (AMPs) are compounds, which have inhibitory activity against microorganisms. In the last decades, AMPs have become powerful alternative agents that have met the need for novel anti-infectives to overcome increasing antibiotic resistance problems. Moreover, recent epidemics and pandemics are increasing the popularity of AMPs, due to the urgent necessity for effective antimicrobial agents in combating the new emergence of microbial diseases. AMPs inhibit a wide range of microorganisms through diverse and special mechanisms by targeting mainly cell membranes or specific intracellular components. In addition to extraction from natural sources, AMPs are produced in various hosts using recombinant methods. More recently, the synthetic analogues of AMPs, designed with some modifications, are predicted to overcome the limitations of stability, toxicity and activity associated with natural AMPs. AMPs have potential applications as antimicrobial agents in food, agriculture, environment, animal husbandry and pharmaceutical industries. In this review, we have provided an overview of the structure, classification and mechanism of action of AMPs, as well as discussed opportunities for their current and potential applications.

Probiotic Lactic Acid Bacteria from Goat’s Milk Potential Producer of Bacteriocin: Evidence from Liquid Chromatography-Mass Spectrometry

The diverse microbial populations in milk produce a range of antimicrobial compounds that confer preservative action. Goat milk characterized by high nutritional value, medicinal properties and hypoallergenic in nature, constitutes the most prevalent non-bovine milk consumed globally. Lactic acid bacteria (LAB), renowned for their probiotic properties, are important constituents of goat milk microflora. In this study, bacterial strains with probiotic potential were isolated and characterized from milk samples of indigenous Indian goat breeds. On MRS medium, Gram-positive rods were observed after anaerobic culture. Based on 16s rRNA technique LAB from goat milk were identified to belong to Enterococcus durans and Lactobacuillus plantarum. Antimicrobial activities were observed against known pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Escherichia. coli and Salmonella typhimurium) and minimum inhibitory concentration was found to be low (6.5 mg/ml) for most of the isolates. High resistance to both acidic condition (pH 2.0) and 0.3% bile salts was observed along with marginal increase in cell counts in some isolates. Adherence to Caco-2 cell lines was observed in all the four identified LABs and was higher in case of Enterococcus durans compared to Lactobacillus plantarum. LC-MS analysis revealed the presence of lacticin as one of the key component of cell free extracts (CFE) of selected isolate. Goat milk as a source of possible LAB probiotics opens up a whole new avenue of probiotics from non-bovine milk sources. LAB strains isolated in this study are potential probiotic candidates that can be employed as antimicrobial agents in food and pharmaceutical industries.

Characterization and bioactivities of silver nanoparticles green synthesized from Vietnamese Ganoderma lucidum

In this study, the utilization of Vietnamese Ganoderma lucidum (G. lucidum) extract was scrutinized under different operational conditions including reaction time, AgNO3:extract mass ratio, and reaction temperature to establish a rapid, cost–effective, and eco–friendly method with a high yield rate and nanoparticle stabilization. The characterization showed that the as–synthesized silver nanoparticles (AgNPs) were well–crystalline with an average size of 11.38 ± 5.51 nm. Meanwhile, the Fourier–transform infrared spectrometry of AgNPs and extract samples showed the absorption bands including –OH stretching, symmetric aliphatic bending, and C–OH stretching vibrations belonging to the presence of polyphenols, triterpenoids, and polysaccharides, respectively. These bands reveal an astounding decline in the polyphenol, triterpenoid, and flavonoid content of the crude G. lucidum extracts, which is consistent with the results obtained from colorimetric methods. In liquid chromatography–mass spectrometry of AgNPs and extract samples, various peaks were detected and they shared significant differences in intensity after the reaction. As a result, the phytochemicals from G. lucidum extracts were confirmed to play the role of reducing silver ions to AgNPs and act as a capping agent to stabilize the colloid mixture. In the biological tests, the colloidal AgNPs demonstrated an extraordinary antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans, with IC50 values of 17.97, 17.06, 1.32, 54.69, and 27.78 µg/mL, respectively. The antioxidant capacity of AgNPs was evaluated using 2,2–diphenyl–1–picrylhydrazyl free radical reagent (IC50 = 447.120 ± 0.084 µg/mL). In addition, the colloidal AgNPs possessed better anticancer activity against the human epidermic carcinoma cancer cell line (KB) with IC50 values of 190.06 ± 3.62 µg/mL when compared to the crude extract. The results of the bioactivity evaluations exhibited the potential utilization of G. lucidum extract as a natural source for the colloidal AgNPs biosynthesis and their application in various areas, particularly as an antimicrobial agent in food, pharmaceutical, and cosmetic product preservation to combat bacterial infection.

Lemongrass and cinnamon oil nanoemulsions: Formulation and study of their physical stability and activity against Zygosaccharomyces bailii.

The optimal conditions for elaborating oil/water nanoemulsions of lemongrass (LG), cinnamon bark (CB) and cinnamon leaves (CL) essential oils and their antimicrobial activity against Zygosaccharomyces bailii at pH 4.00 were studied. The effect of the emulsification methodology on the physical stability and antimicrobial activity of the nanoemulsions were also evaluated. Furthermore, the sensory impact of nanoemulsions added to an apple juice was tested. LG and CL nanoemulsions were elaborated by ultrasonication and CB nanoemulsion, by high-speed homogenization. They were stable for at least 120 days at 25 °C. They exhibited antimicrobial activity against Z. bailii being CB the most effective since it showed the smallest MIC value (156.3 mg/l), followed by LG (468.8 mg/l) and CL (1250.0 mg/l). A slight increase in growth rate was observed due to ultrasonication. An additive interaction in relation to the inhibitory effect between LG and CB nanoemulsions against Z. bailii was observed. While nanoemulsions obtained would be used as natural antimicrobial agents in food and beverage products, only LG nanoemulsion at MIC concentration diluted was acceptable in juice showing the sensory impact of essential oils on foods.

O-004. Circulating SIGLEC6 is deranged in preeclampsia and may be a biomarker of disease severity

In this study, the utilization of Vietnamese Ganoderma lucidum (G. lucidum) extract was scrutinized under different operational conditions including reaction time, AgNO3:extract mass ratio, and reaction temperature to establish a rapid, cost–effective, and eco–friendly method with a high yield rate and nanoparticle stabilization. The characterization showed that the as–synthesized silver nanoparticles (AgNPs) were well–crystalline with an average size of 11.38 ± 5.51 nm. Meanwhile, the Fourier–transform infrared spectrometry of AgNPs and extract samples showed the absorption bands including –OH stretching, symmetric aliphatic bending, and C–OH stretching vibrations belonging to the presence of polyphenols, triterpenoids, and polysaccharides, respectively. These bands reveal an astounding decline in the polyphenol, triterpenoid, and flavonoid content of the crude G. lucidum extracts, which is consistent with the results obtained from colorimetric methods. In liquid chromatography–mass spectrometry of AgNPs and extract samples, various peaks were detected and they shared significant differences in intensity after the reaction. As a result, the phytochemicals from G. lucidum extracts were confirmed to play the role of reducing silver ions to AgNPs and act as a capping agent to stabilize the colloid mixture. In the biological tests, the colloidal AgNPs demonstrated an extraordinary antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans, with IC50 values of 17.97, 17.06, 1.32, 54.69, and 27.78 µg/mL, respectively. The antioxidant capacity of AgNPs was evaluated using 2,2–diphenyl–1–picrylhydrazyl free radical reagent (IC50 = 447.120 ± 0.084 µg/mL). In addition, the colloidal AgNPs possessed better anticancer activity against the human epidermic carcinoma cancer cell line (KB) with IC50 values of 190.06 ± 3.62 µg/mL when compared to the crude extract. The results of the bioactivity evaluations exhibited the potential utilization of G. lucidum extract as a natural source for the colloidal AgNPs biosynthesis and their application in various areas, particularly as an antimicrobial agent in food, pharmaceutical, and cosmetic product preservation to combat bacterial infection.

Optimization and Comparison of Ultrasound and Microwave-Assisted Extraction of Phenolic Compounds from Cotton-Lavender (Santolina chamaecyparissus L.)

The interest in natural phenolic compounds has increased because of their attractive use especially as antioxidant and antimicrobial agents in foods. The large content in phenolic compounds of interest in Santolina chamaecyparissus L. (S. chamaecyparissus) makes this plant a target source that is worthy of note. In this work, new extraction technologies comprising ultrasound (UAE) and microwave (MAE) assisted extraction of the phenolic compounds in S. chamaecyparissus have been developed, optimized, and compared. Several extraction factors have been optimized based on a Box-Behnken design. Such optimized factors include the percentage of methanol in water (25–75%), the temperature (10–70 °C), the ultrasound amplitude (20–80%), the ultrasound cycle (0.2–1 s), the solvent pH (2–7) and the solvent-sample ratio (5/0.2–15/0.2 mL/g) with regard to UAE, while the percentage of methanol in water (50–100%), the temperature (50–100 °C), the pH (2–7) and the solvent-sample ratio (5/0.2–15/0.2 mL/g) were optimized for MAE. The solvent composition was the most influential parameter both on MAEs (64%) and UAEs (74%). The extraction optimum time was established as 15 min for MAE and 25 min for UAE. Five major phenolic compounds were detected and identified by Ultra-High-Performance Liquid Chromatography—Quadrupole Time of Flight—Mass Spectrometry (UHPLC-QToF-MS) in the extracts: chlorogenic acid, quercetin 3-O-galactoside, quercetin 3-O-glucoside, isoorientin, and cynarin. With the exception of chlorogenic acid, the other four compounds have been identified for the first time in S. chamaecyparissus. The findings have confirmed that MAE is a significantly more efficient extraction method than UAE to extract phenolic compounds from S. chamaecyparissus.

Assessment of Antioxidant and Antimicrobial Activities of Silver Nanoparticles Biosynthesized by Haplophyllum Obtusifolium

Background: Plants comprise great antioxidant sources as a result of their redox and biochemical components, which are rich in secondary metabolites such as phenolic acids, flavonoids, and other constituents. Haplophyllum obtusifolium from polygonaceae is widely used for preventing and managing diabetes. This study investigated the antibacterial and antioxidant activities of silver nanoparticles (AgNPs) biosynthesized by H. obtusifolium. Methods: The aerial parts of H. obtusifolium were gathered from the north of Khorasan Razavi province, Iran and desiccated at the chamber temperature. The shoots were powdered by grinding, 5 g of the powder was mixed with 250 mL of deionized water, and the resultant blend was then filtered. Bactericidal properties and antioxidant activity of the nanoparticles were assessed using disk diffusion and DPPH (2, 2-diphenyl-1-picrylhydrazyl) tests, respectively. Results: The results of this study showed that the biosynthesized nanoparticles exhibited antibacterial activity against a gram-negative (Klebsiella pneumoniae) bacterium, but they had no effects on gram-positive Staphylococcus epidermidis. Antioxidant test results showed that these nanoparticles were capable of eliminating DPPH radicals in a concentration-dependent manner so that a more potent antioxidant activity was seen in higher concentrations of the nanoparticles. Conclusion: Our results suggested that H. obtusifolium can be used as a key source of antioxidants/ antimicrobial agents in food and pharmaceutical industries.

Evaluating the applicability of the modified four-plate test on the determination of antimicrobial agent residues in pork

The antibiotic residues in 1,022 pork carcass samples, which were collected from 19 areas in Taipei, Taichung and Kaohsiung counties between January and June, 1997, were systematically investigated using a modified four-plate test (MFPT). Four culture media inoculated with 3 strains of bacteria were used; two were inoculated with Bacillus subtilis at pH 6.0 and pH 8.0, and the third and fourth were inoculated with Bacillus cereus and Sarcina lutea, respectively. The identification and quantification of tetracycline residues in the raw meat was performed by bioassay and bioautography. Streptomycin and chloramphenicol in pork carcasses were screened by ELISA and further quantified using the HPLC method. Results showed that using the CNS 5916 method, only 1 out of 1,022 test samples (0.1%) was detected to contain an antimicrobial agent. While using the MFPT method, 4.11% and 0.64% test samples were found to contain tetracycline and streptomycin residues, respectively. No chloramphenicol residue was detected in any tested samples. It was concluded that the MFPT method is practical, sensitive, less expensive, and simple as compared to the CNS 5916 and FPT methods, which are routinely used in Taiwan and the European Community, respectively. MFTP is therefore recommended as an official method to assay the antimicrobial agents in foods.

Microcin J25 Exhibits Inhibitory Activity Against Salmonella Newport in Continuous Fermentation Model Mimicking Swine Colonic Conditions.

Microcin J25 (MccJ25), a 21-amino acid bacteriocin produced by Escherichia coli (E. coli), is a potent inhibitor of Enterobacteriaceae, including pathogenic E. coli, Salmonella, and Shigella. Its lasso structure makes it highly stable and therefore of interest as a possible antimicrobial agent in foods or as an alternative to antibiotics in livestock production. In the present study, we aimed to evaluate in vitro the inhibitory activity of MccJ25 against Salmonella enterica subsp. enterica serovar Newport ATCC 6962 (Salmonella Newport) used as a model pathogen under conditions simulating those of the swine proximal colon. The growth inhibition activity of MccJ25 against Salmonella Newport was examined in lysogeny broth (LB) and in modified MacFarlane medium that allows miming the swine colonic conditions. The MccJ25 activity was further determined using the Polyfermentor intestinal model (PolyFermS), an in vitro continuous fermentation model that permits deciphering the activity of any antimicrobial molecule in real colon fermentation conditions using selected microbiota. It was set up here to simulate the porcine proximal colon fermentation. In these conditions, the inhibition activity of MccJ25 was compared to those of two antimicrobial agents, reuterin and rifampicin. The minimal inhibitory concentration (MIC) of MccJ25 was determined at 0.03 μM in LB medium, compared to 1,079 and 38 μM for reuterin and rifampicin, respectively, showing a significantly higher potency of MccJ25. Total inhibition of Salmonella Newport was observed in LB medium over 24 h of incubation at concentrations starting from the MIC. In the PolyFermS model, MccJ25 induced a significantly stronger inhibition of Salmonella Newport growth than reuterin or rifampicin. A specific and sensitive LC-MS method allowed to detect and quantify MccJ25 in the PolyFermS fermentation system, showing that MccJ25 remains stable and active against Salmonella in conditions mimicking those found in swine colon. This study paves the way for further exploring the potential of this bacteriocin as an alternative to antibiotics in livestock.

New Insights into the Antimicrobial Properties of Hydrolysates and Peptide Fractions Derived from Chia Seed (Salvia hispanica L.).

Bioactive peptides derived from chia (Salvia hispanica) seed with antioxidant, antihypertensive, and anti-inflammatory activities have been well documented; however, few studies describe the antimicrobial properties of these peptides, which is of great interest not only in the prevention of food-borne diseases but also food spoilage. The aim of this study was to generate chia seed peptides using microwave-assisted hydrolysis with sequential (alcalase + flavourzyme) enzymes (AF-MW), fractionate them into 3-10 and < 3kDa fractions, and evaluate their potential antimicrobial activity towards Escherichia coli, Salmonella enterica, and Listeria monocytogenes. Overall, the peptide fraction < 3kDa showed higher antimicrobial activity than both chia seed hydrolysate and peptide fraction 3-10kDa. Furthermore, the < 3kDa fraction showed remarkable increase in membrane permeability of E. coli (71.49% crystal violet uptake) and L. monocytogenes (80.10% crystal violet uptake). These peptides caused a significant extension in the lag phase, decreases in the maximum growth, and growth rate in the bacteria and promoted multiple indentations (transmembrane tunnels), membrane wrinkling, and pronounced deformations in the integrity of the bacterial cell membranes. Finally, a select group of peptides in the AF-MW < 3kDa fraction contained 16 sequences with cationic and hydrophobic character, with seven of them sharing the exact same sequence (GDVIAIR) and eight of them having the amino acid K as either N- or C-terminal or both. In conclusion, our results indicate that bioactive peptides obtained from chia seed proteins by microwave and enzymatic hydrolysis could be employed as antimicrobial agents in foods and therapeutic applications.

Anti-Salmonella mode of action of natural L-phenyl lactic acid purified from Lactobacillus plantarum ZJ316.

Salmonella is a serious foodborne pathogen responsible for more than 90 million cases of gastroenteritis worldwide annually. Due to the gradual increase in antibiotic-resistant Salmonella strains, the identification of natural antibacterial substances is urgently needed. Herein, we purified natural L-phenyl lactic acid (L-PLA) from Lactobacillus plantarum ZJ316 and revealed its antimicrobial mode against Salmonella enterica subsp. enterica ATCC 14028. L-PLA (98.14% pure) was obtained using the macroporous resin XAD-16, solid-phase extraction (SPE), reverse-phase high-performance liquid chromatography (RP-HPLC), and chiral chromatography. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that the cell morphology was severely compromised. Transmembrane electrical potential (ΔΨ), transmembrane pH gradient (ΔpH), intracellular ATP level, extracellular electrical conductivity (EC), and genomic DNA analyses were employed to evaluate the antibacterial mode of action of L-PLA. The proton motive force (PMF) and ATP of Salmonella cells rapidly dissipated, and the EC markedly increased. The gel retardation assay demonstrated that L-PLA could bind to genomic DNA and intercalate into the nucleic acids. The anti-Salmonella mode of action of L-PLA was attributed to the destruction of the cell membrane and genomic DNA binding. This research suggests that L-PLA has potential applications as an antimicrobial agent in food, medicine, and other fields. KEY POINTS: • Natural L-PLA was purified from L. plantarum ZJ316 with a purity of 98.14%. • L-PLA effectively inhibited Salmonella strains by antibacterial activities and MICs. • Membrane destruction and binding with DNA are the anti-Salmonella modes of L-PLA.

The Antimicrobial Activity of Enteromorpha sp. Methanolic Extract and Gelatin Film Solution Against on Some Pathogens

Pathogenic microorganisms have been the primary cause of foodborne disease and food poisoning throughout the world for years. The use of natural antimicrobial agents in food coating has been effective in regulating the adverse effects of pathogens in food. Increasing antimicrobial efficacy in these coatings is one of the current issues of the food industry. In the present study, the antimicrobial properties of Enteromorpha sp., which is a marine algae, and gelatin film solution incorporated with Enteromorpha sp. methanol extract have been investigated. The contents of Enteromorpha sp. methanol extract were determined by Gas chromatography–mass spectrometry (GCMS). The most important components in the extract were methyl palmitoleate, neophytadiene, phytol, methyl linolenate and methyl stearate. The minimum inhibitory concentration (MIC; the lowest concentration of test material which results in 99.9% inhibition of growth) of Enteromorpha sp. on Escherichia coli, Staphylococcus aureus and Candida albicans were found to be between 10.79 mg/mL and 26.86 mg/mL by spectrophotometric microdilution technique. The antimicrobial effect of gelatin- Enteromorpha sp. methanolic extract film solution against the same pathogens was determined by disc diffusion method. The inhibition zone of gelatin- Enteromorpha sp. film solution was reported between 0.1 and 5.1 mm against pathogens. After a 24-h incubation, the effectiveness of the film solution was lower (1.3 mm) when compared to the extract on E. coli (5.1 mm). As a result, this study clearly showed that Enteromorpha sp. could be used as antimicrobial food coating agent, especially, in E. coli struggle.