Natural Antimicrobial Substances Research Articles

Identification and Characterization of a Bacteriocin from the Newly Isolated Bacillus subtilis HD15 with Inhibitory Effects against Bacillus cereus.

Natural antimicrobial substances are needed as alternatives to synthetic antimicrobials to protect against foodborne pathogens. In this study, a bacteriocin-producing bacterium, Bacillus subtilis HD15, was isolated from doenjang, a traditional Korean fermented soybean paste. We sequenced the complete genome of B. subtilis HD15. This genome size was 4,173,431 bp with a G + C content of of 43.58%, 4,305 genes, and 4,222 protein-coding genes with predicted functions, including a subtilosin A gene cluster. The bacteriocin was purified by ammonium sulfate precipitation, Diethylaminoethanol-Sepharose chromatography, and Sephacryl gel filtration, with 12.4-fold purification and 26.2% yield, respectively. The purified protein had a molecular weight of 3.6 kDa. The N-terminal amino acid sequence showed the highest similarity to Bacillus subtilis 168 subtilosin A (78%) but only 68% similarity to B. tequilensis subtilosin proteins, indicating that the antimicrobial substance isolated from B. subtilis HD15 is a novel bacteriocin related to subtilosin A. The purified protein from B. subtilis HD15 exhibited high antimicrobial activity against Listeria monocytogenes and Bacillus cereus. It showed stable activity in the range 0-70°C and pH 2-10 and was completely inhibited by protease, proteinase K, and pronase E treatment, suggesting that it is a proteinaceous substance. These findings support the potential industrial applications of the novel bacteriocin purified from B. subtilis HD15.

A review on antimicrobial activities of some culinary herbs and spices against Staphylococcus aureus

Food safety is of great importance all over the world as it concerns consumer health. All employees in the food chain must comply with the hygiene rules. One of the important issues that threaten food safety is contamination with microorganisms. Numerous people are affected by contaminated and/or poorly preserved food and outbreaks have occurred. The World Health Organization (WHO) draws attention to human health and economic losses in this respect. From ancient times, herbs and spices are utilized in Türkiye and various parts of world to enhance the flavor of food and their sensory properties. It is also possible to prevent the development of Staphylococcus aureus, which causes food poisoning, thanks to the antibacterial properties of culinary herbs or spices. Thus, using natural antimicrobial substances from spices and herbs may be an alternative for inhibition/elimination of growth of S. aureus extending the shelf life without synthetic preservatives. This review aims to explain foodborne diseases and their global burden, staphylococcal food poisoning, natural antimicrobials, some edible herbs in Türkiye: their culinary uses and antibacterial efficacy against S. aureus.

Utilization of RSM for optimization of physical variables to improve bacteriocin production from Lactobacillus plantarum strain MS

The utilization of natural antimicrobial substances has been increased in the pharmaceutical sector due to their stability and inhibition activity against pathogenic microorganisms. In the current study, the bacteriocin synthesis by locally isolated Lactobacillus plantarum MS from yogurt, has been optimized by using response surface methodology. Statistical optimization of physical variables by using Box-Behnken design, 3200 AU/mL bacteriocin activity was detected at 30 C temperature, 18h incubation time, and pH 6 against Staphylococcus aureus. The resulting bacteriocin was found to be stable a broad range of pH (2-12) and temperature (37-100 C) but the activity of bacteriocin was slightly disturbed at 121 C. Besides, bacteriocin showed stability after treatment with various enzymes (catalase, amylase, and lipase), salt (NaCl), and surfactants (triton X-100, EDTA, and SDS) but found sensitive by treating with proteolytic enzymes (proteinase K and trypsin) in comparison with untreated bacteriocin. Because of such biochemical characteristics, these antibacterial peptides could be possibly incorporated in the field of pharmacy to fulfil consumers' demand for natural remedies. Keywords: Lactic acid bacteria, bacteriocin, antibacterial activity, response surface methodology, Box-Behnken design.

Insights into the Role of Biopolymer-Based Xerogels in Biomedical Applications.

Xerogels are advanced, functional, porous materials consisting of ambient, dried, cross-linked polymeric networks. They possess characteristics such as high porosity, great surface area, and an affordable preparation route; they can be prepared from several organic and inorganic precursors for numerous applications. Owing to their desired properties, these materials were found to be suitable for several medical and biomedical applications; the high drug-loading capacity of xerogels and their ability to maintain sustained drug release make them highly desirable for drug delivery applications. As biopolymers and chemical-free materials, they have been also utilized in tissue engineering and regenerative medicine due to their high biocompatibility, non-immunogenicity, and non-cytotoxicity. Biopolymers have the ability to interact, cross-link, and/or trap several active agents, such as antibiotic or natural antimicrobial substances, which is useful in wound dressing and healing applications, and they can also be used to trap antibodies, enzymes, and cells for biosensing and monitoring applications. This review presents, for the first time, an introduction to biopolymeric xerogels, their fabrication approach, and their properties. We present the biological properties that make these materials suitable for many biomedical applications and discuss the most recent works regarding their applications, including drug delivery, wound healing and dressing, tissue scaffolding, and biosensing.

Self-Disinfecting Paints with the Natural Antimicrobial Substances: Colophony and Curcumin.

The risk of infection arising from indirect sources—namely, contaminated surfaces—has been proved, particularly in healthcare facilities. In the attempt to minimize this problem, innumerable research projects involving the development of surfaces with self-disinfecting properties are being conducted. In this work, wall-paints with self-disinfecting properties were developed with the scope of being applied in environments prone to contamination, such as those at healthcare settings. Our approach was to develop new paint formulations containing two natural plant-based products with known antimicrobial activity—colophony (CLF) and curcumin (CUR). The natural substances were separately incorporated on a commercial paint and their antibacterial activity was evaluated with several bacterial species following ISO 22196. To assess the paints’ safety, cytotoxicity tests were performed on HaCaT and A549 cell lines, using tests on extracts and direct contact tests, as suggested by the standardized protocol ISO 10993. In general, both paints containing CLF and CUR were able to reduce the bacterial growth after 24 h, compared with the control, the commercial unmodified paint. Colophony was even able to reduce the number of culturable bacteria by over 2 log for Staphylococcus aureus, Escherichia coli, and Bacillus cereus. Regarding the cytotoxicity tests performed (WST-1, NRU, and LDH), both formulations revealed promising results regardless of the methodology used.

Characteristics of the Polyphenolic Profile and Antioxidant Activity of Cone Extracts from Conifers Determined Using Electrochemical and Spectrophotometric Methods.

The aim of the study was to analyze the polyphenolic profile of cone extracts of Douglas fir, Scots pine and Korean fir, and to study their antioxidant activity. The mechanism of electro-oxidation of polyphenols (such as procyanidins and catechins) from cone extracts was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), as well as spectrophotometric methods—ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power ) and CUPRAC (CUPric Reducing Antioxidant Capacity). The scientific novelty of the research is the comprehensive analysis of cone extracts in terms of antioxidant properties. Due to the high polyphenol content, the extracts showed significant ability to reduce oxidative reactions, as well as the ability to scavenge free radicals and transition metal ions. Douglas fir, Scots pine and Korean fir cone extracts can potentially be used as natural stabilizers, preservatives and antimicrobial substances in the food industry and in medications.

The Effects of Natural Products and Environmental Conditions on Antimicrobial Resistance.

Due to the extensive application of antibiotics in medical and farming practices, the continued diversification and development of antimicrobial resistance (AMR) has attracted serious public concern. With the emergence of AMR and the failure to treat bacterial infections, it has led to an increased interest in searching for novel antibacterial substances such as natural antimicrobial substances, including microbial volatile compounds (MVCs), plant-derived compounds, and antimicrobial peptides. However, increasing observations have revealed that AMR is associated not only with the use of antibacterial substances but also with tolerance to heavy metals existing in nature and being used in agriculture practice. Additionally, bacteria respond to environmental stresses, e.g., nutrients, oxidative stress, envelope stress, by employing various adaptive strategies that contribute to the development of AMR and the survival of bacteria. Therefore, we need to elucidate thoroughly the factors and conditions affecting AMR to take comprehensive measures to control the development of AMR.

Lipid-Based Nanostructures for the Delivery of Natural Antimicrobials.

Encapsulation can be a suitable strategy to protect natural antimicrobial substances against some harsh conditions of processing and storage and to provide efficient formulations for antimicrobial delivery. Lipid-based nanostructures, including liposomes, solid lipid nanoparticles (SLNs), and nanostructured lipid nanocarriers (NLCs), are valuable systems for the delivery and controlled release of natural antimicrobial substances. These nanostructures have been used as carriers for bacteriocins and other antimicrobial peptides, antimicrobial enzymes, essential oils, and antimicrobial phytochemicals. Most studies are conducted with liposomes, although the potential of SLNs and NLCs as antimicrobial nanocarriers is not yet fully established. Some studies reveal that lipid-based formulations can be used for co-encapsulation of natural antimicrobials, improving their potential to control microbial pathogens.

Effect of Natural Antimicrobial Substances with Packaging System on Improving Quality of ‘ETMANI’ Guava (Psidium guajava L.) Fruit during cold storage

The effect of postharvest treatments of thyme oil and chitosan under different concentrations and combined with the packaging on weight loss%, firmness, decay index, malondialdehyde(MDA) content, total chlorophyll, hue angle (ho), ripening index, ascorbic acid and pectin methylesterase enzyme(PME) on ‘Etmani’ guava (Psidium guajava L.) fruit, were investigated during 2017 and 2018 successive seasons. Obtained results indicate that weight loss %was diminished by (T7) thyme oil at 1000 μLL−1 + packaging and (T8) chitosan at 1% + packaging, as well as firmness and PME were reduced significantly (p˂0.05) when treated with chitosan at 1% and 2% (T3 and T 4) and thyme oil at 1000 μLL−1 ( T2) compared to control treatment (T0). Simultaneously, it indicated that the most effective treatment in decreasing MDA and decay index were the treatment T3 and T4. Therefore, Chitosan and Thyme oils treatments could maintain normal cell membrane structure and function through down-regulating MDA content and pectin methylesterase enzyme activity, which due to reducing softening, weight loss%, and decay index in guava cv. ‘Etmani’ fruits during storage periods in comparison to other treatments and control

Inorganic Nanocarriers for Encapsulation of Natural Antimicrobial Compounds for Potential Food Packaging Application: A Comparative Study.

Design and development of novel inorganic nanocarriers for encapsulation of natural antimicrobial substances for food packaging applications have received great interest during the last years. Natural nanoclays are the most investigated nanocarriers and recently interest has also grown in the synthetically produced porous silica particles. However, these different carrier matrices have not been compared in terms of their loading capability and subsequent release. In this study, the feasibility of porous silica particles (with different pore structures and/or surface functionalities) and commercially available nanoclays were evaluated as encapsulation matrices. Two well-studied antimicrobial substances, thymol and curcumin, were chosen as volatile and non-volatile model compounds, respectively. The encapsulation efficiency, and the subsequent dispersibility and release, of these substances differed significantly among the nanocarriers. Encapsulation of the volatile compound highly depends on the inner surface area, i.e., the protective pore environment, and an optimal nanocarrier can protect the encapsulated thymol from volatilization. For the non-volatile compound, only the release rate and dispersibility are affected by the pore structure. Further, water-activated release of the volatile compound was demonstrated and exhibited good antimicrobial efficacy in the vapor phase against Staphylococcus aureus. This comparative study can provide a base for selecting the right nanocarrier aimed at a specific food packaging application. No nanocarrier can be considered as a universally applicable one.

Enterococcus faecium CMUL1216 an Immunobiotic Strain with a Potential Application in Animal Sector.

Antibiotic misuse in the animal sector is the first cause of the emergence and spreading of MDR bacteria. Prevention of infectious diseases and enhancement of animal growth are the main effects of antibiotics that push farmers and veterinarians to use this molecule in animal farms. Thus, the use of alternative solutions such as natural antimicrobial substances as well as probiotic strains is a crucial need in this sector. Enterococcus faecium CMUL1216 was isolated from healthy human baby's feces. This strain was assessed in vitro for probiotic properties including activity against many pathogens isolated from animal, human, and soil samples. CMUL1216 strain exhibits good antimicrobial activity against indicator pathogens in both planktonic and biofilm forms. In addition, CMUL1216 strain showed a strong biofilm formation. Furthermore, CMUL1216 exhibits a good anti-inflammatory effect by inducing the secretion of IL-10 in vitro. Moreover, this strain did not show any pathogenic characteristics such as hemolytic effect, presence of virulence genes as well as susceptibility to the majority of antibiotic families. E. faecium CMUL1216 could be a good candidate to be used a probiotic strain in the animal sector in order to maintain animal health and therefore reduce antibiotic resistance caused by the excessive use in this sector.

Antimicrobial Efficiency of Moringa oleifera Leave Extracts against Some Multidrug Resistant Pathogen

THE MEDICINAL plants have vital sources of natural antimicrobial substances for human health avoiding side effects precipitated by using synthetic chemical. The decreasing effectiveness of traditional antibiotics towards multi drug resistant microorganism is a global public health. It was found that the mixtures between different plant extract and commercial antibiotics increased the effectiveness of antibiotics multi drug resistant bacteria. The combinations between different plant extract and commercial antibiotics increased the effectiveness of antibiotics against multi drug resistant strains. Extracts of Moringa oleifera leaves showed remarkable antimicrobial activity against the growth of the gram positive and negative bacteria drug resistant clinical strains (Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 29737 and Staph epidermidis ATCC 12228, Bacillus pumilis ATCC 14884, Micrococcus luteus ATCC 10240, Bordetella sp, Bacillus subtilis and Klebsiella sp . Antimicrobial activity of methanol extract of Moringa oleifera leaves (MML) using well diffusion method was higher (30mm inhibition zone) than ethanolic and aqueous extract. The minimum inhibition concentration (MIC) of the selected pathogenic bacteria ranged between 23 -800μg/ml. The interactions between different extract of Moringa oleifera leaves and different antibiotic groups of Ampicillin (Am10), Amoxicillin (AMC30), Amikacin (AK30), Gentamycin (CN10), Tetracycline (TE30), Erythromycin (E15), Bacitracin (B10) were conducted using agar diffusion method against the selected pathogenic bacteria. Methanol extract of Moringa oleifera leaves could be used as a source for resistance-modifying agents against infectious multi-drug resistant bacteria.

Physical, Thermal, and Antibacterial Effects of Active Essential Oils with Potential for Biomedical Applications Loaded onto Cellulose Acetate/Polycaprolactone Wet-Spun Microfibers.

New approaches to deal with the growing concern associated with antibiotic-resistant bacteria are emerging daily. Essential oils (EOs) are natural antimicrobial substances with great potential to mitigate this situation. However, their volatile nature, in their liquid-free form, has restricted their generalized application in biomedicine. Here, we propose the use of cellulose acetate (CA)/polycaprolactone (PCL) wet-spun fibers as potential delivery platforms of selected EOs to fight infections caused by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Twenty EOs were selected and screened for their minimal inhibitory concentration (MIC), using the antibiotic ampicillin as positive control. The cinnamon leaf oil (CLO), cajeput oil (CJO), and the clove oil (CO) were the most effective EOs, against the Gram-positive (MIC < 22.38 mg/mL) and the Gram-negative (MIC < 11.19 mg/mL) bacteria. Uniform microfibers were successfully wet-spun from CA/PCL with an averaged diameter of 53.9 ± 4.5 µm, and then modified by immersion with CLO, CJO and CO at 2 × MIC value. EOs incorporation was confirmed by UV-visible spectroscopy, Fourier-transformed infrared spectroscopy, and thermal gravimetric analysis. However, while microfibers contained ampicillin at MIC (control) after the 72 h modification, the CLO, CO and CJO-loaded fibers registered ≈ 14%, 66%, and 76% of their MIC value, respectively. Data showed that even at small amounts the EO-modified microfibers were effective against the tested bacteria, both by killing bacteria more quickly or by disrupting more easily their cytoplasmic membrane than ampicillin. Considering the amount immobilized, CLO-modified fibers were deemed the most effective from the EOs group. These results indicate that CA/PCL microfibers loaded with EOs can be easily produced with increased antibacterial action, envisioning their use as scaffolding materials for the treatment of infections.

Salix babylonica L. as a Natural Anticoccidial Alternative in Growing Rabbits.

Coccidiosis in rabbit production is responsible for high morbidity, mortality, and economic losses. The use of natural antimicrobial substances in rabbits represents a promising way to improve their health and production. The aim of the present study was to assess the activity of Salix babylonica hydroalcoholic extract (SBHE) on the elimination of Eimeria spp. in rabbits. The phytochemical compounds and chemical composition of SBHE were determined. The cytotoxicity of SBHE was determined by a microwell assay using Artemia salina. Twenty-five New Zealand rabbits, 28 days old and 872 ± 171 g body weight (BW), were used in a completely randomized design. The rabbits were assigned to five groups of five rabbits, control group (A) received only basal diet (BD), B group received BD + 25 mg/kg BW of SBHE, C group received BD + 50 mg/kg BW of SBHE, D group received BD + 100 mg/kg BW of SBHE, and E group received BD + coccidiostat Baycox® (75 mg/kg body weight) for 28 days. Feces samples were collected at days 0, 7, 14, 21, and 28; morphological and morphometric identifications of Eimeria were carried out by the flotation technique and counting of oocysts by the McMaster technique. The rabbits were found naturally infected with Eimeria spp. The SBHE present phytochemicals with anticoccidial activity, and the cytotoxicity test indicate that this extract is nontoxic. This study demonstrates that oral administration of SBHE at 25 and 50 mg/kg BW reduced the release of oocysts per gram of feces. This effect was observed at day 14 and had the most significant effect at day 28 for both concentrations. The results indicate that SBHE could be a natural alternative for the control of coccidiosis in rabbit production.

Effect of Chitosan-Ascorbic Acid Coatings on the Refrigerated Storage Stability of Fresh-Cut Apples

Using natural antimicrobial substances in edible films becomes crucial to extend the shelf-life of fresh-cut fruits due to the consumers’ preferences. In this study chitosan and ascorbic acid based film was used to improve the shelf-life of fresh-cut apples. Fresh-cut apple cubes were dipped in water (control), ascorbic acid (1%) or mixtures of chitosan–ascorbic acid in different ratios (1%:1%, 2%:2% or 1%:5%) for 5 min. After draining, fresh-cut apples were packed in sterile polypropylene jars and stored at 5 °C for 14 days. The treatment with chitosan and ascorbic acid suppressed browning, retained flesh firmness and maintained phenolic compounds throughout the storage period. Moreover, the treatment with chitosan–ascorbic acid significantly retarded the microbial growth during storage. Those findings suggested that the best performance was acquired in 1% chitosan and 5% ascorbic acid coating. That coating could be practical and useful to prolonging the chemical and microbial shelf lives of fresh-cut apples during refrigerated storage.

Response surface modeling for the inactivation of Bacillus cereus on cooked spinach by natural antimicrobials at various temperatures

AbstractThis study was conducted to investigate the growth of Bacillus cereus on cooked spinach with natural antimicrobial substances (0.00–0.02% thymol, 0.60–1.30% acetic acid, and 0.00–0.05% nisin) at various temperatures (15, 25, and 35°C) in order to find the best combination of inhibition. Response surface modeling with the Gompertz model equation was used to describe the growth of B. cereus vegetative cells on cooked spinach with natural antimicrobial substances as a function of temperature. The specific growth rate of B. cereus at the highest concentration of thymol (0.02%) was lower than with the other treatments. In particular, the lag time of B. cereus was the longest for combinations thymol 0.02%, acetic acid 0.68%, and nisin 0.03% at 25°C. The predicted values were shown to be significantly in good agreement with experimental values because the adjusted determination coefficient ( ) was 0.91 and the level of significance was p &lt; .0001. Besides, bias factor (Bf) values of the SGR and LT for B. cereus were 1.07 and 1.10, respectively, indicating that they were mostly at the acceptable level. In sensory evaluation, appearance and color of cooked spinach with antimicrobial substances was similar to the control.Practical applicationsNatural antimicrobials could be used as the preservation method to improve the food safety of cooked foods such as cooked vegetables.

SOUS VIDE TECHNOLOGY — SEVERAL ASPECTS OF QUALITY AND MICROBIOLOGICAL SAFETY

Worsening of the demographic situation (a decline in the birth rate, a growth in the proportion of the elderly and so on), changes in eating habits associated with the changes in the pace of life, a desire of the increasing number of people to consume «healthy» products and not to spend much time on their preparation led to an increase in the demand for convenient ready-to-cook meat products that retain healthy components. As a result, the minimal processing technologies such as sous vide are finding ever increasing use. Sous vide is a technology of low temperature thermal processing of food under vacuum. Preparation of food by sous vide technology allows reliable control of product sensory indicators and microbiological safety with strict adherence to the temperature-time regimes of processing and storage taking into consideration the fact that relatively mild thermal processing may not ensure death of all vegetative cells and does not inactivate spores. To enhance the microbiological safety of these products, several additional methods of treatment with the use of natural antimicrobial substances can be applied. The paper presents a review of scientific studies aimed at investigation of an effect of the sous vide technology on changes in quality indicators and microbiological safety of sous vide products.

Antimicrobial activity of some plant extracts against bacterial pathogens isolated from faeces of red deer (Cervus elaphus).

Antibacterial activity is the most widely studied aspect of plant extracts. Antibiotics extensively produced and consumed in large quantities, have proved to be problematic due to various types of adverse effects. The development of bacterial resistance to currently available antibiotics has necessitated the search for new antibacterial agents. One of the alternative strategies for fighting antibiotic- resistant bacteria is the use of natural antimicrobial substances such as plant extracts. We tested the antimicrobial activity of nine extracts from different plants against pathogenic bacteria isolated from the faeces of red deer (Cervus elaphus). Selected bacteria commonly contaminated the natural environment and constitute a source of infection in other animals and humans. Extracts obtained from the following plants were tested: Hypericum perforatum L., Chamomilla recutita L., Achillea millefolium L., Salvia officinalis L., Thymus vulgaris L., Pinus sylvestris L., Mentha x piperita L., Valeriana officinalis L. and Foeniculum vulgare Mill. The highest degree of antibacterial properties was observed for Mentha x piperita L., narrower spectrum of activity possessed Hypericum perforatum L. Extracts of Achillea millefolium L. had the lowest spectrum of antibacterial activity. Our study confirms that many plant extracts shows in vitro antibacterial activity.

Chemical profiling and antimicrobial activity of essential oil from Curcuma aeruginosa Roxb., Curcuma glans K. Larsen & J. Mood and Curcuma cf. xanthorrhiza Roxb. collected in Thailand

ObjectiveTo investigate chemical constituents and new antimicrobial agents among essential oils from the rhizomes of Curcuma aeruginosa (C. aeruginosa) Roxb., Curcuma glans K. Larsen & J. Mood and Curcuma cf. xanthorrhiza Roxb. MethodsThe essential oils were obtained by hydro-distillation and analyzed by gas chromatography/mass spectroscopy. Agar-well diffusion assay was used to study the anti-microbial activity and also broth-micro dilution techniques were examined for minimum inhibitory concentration (MIC) against four bacterial strains and yeast. ResultsThe gas chromatography/mass spectroscopy analysis showed monoterpenes predominantly (88.53%) in the rhizome oil of Curcuma cf. xanthorrhiza. Sesquiterpenes (50.10%) was the most abundant component in the essential oil of C. glans, while monoterpenes (45.55%) and sesquiterpenes (45.81%) were found in C. aeruginosa with a significant amount. The major components of C. aeruginosa were characterized as camphor (29.39%) and germacrone (21.21%). Germacrone (15.76%), β-pinene (9.97%) and camphor (9.96%) were found as major compounds in the rhizome oils of C. glans while α-terpinolene (24.86%) and p-cymen-7-ol (12.17%) were found as major compositions in Curcuma cf. xanthorrhiza. The essential oils were tested against four bacterial strains and yeast. As a result, the rhizome oil of C. aeruginosa exhibited potent activity against Staphylococcus aureus [inhibition zone (21.94 ± 0.24) mm, MIC 125 μg/mL], Bacillus cereus [inhibition zone (20.83 ± 0.36) mm, MIC 125 μg/mL], and Candida albicans [inhibition zone (11.60 ± 0.30) mm, MIC 250 μg/mL]. ConclusionsThe essential oils from three Curcuma species possessed greater activity against the gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) than gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The results suggest that the essential oils from the fresh rhizome of Curcuma spp. might be a potential source of natural antimicrobial substances.

Antimicrobial evaluation of novel poly-lactic acid based nanocomposites incorporated with bioactive compounds in-vitro and in refrigerated vacuum-packed cooked sausages

Biodegradability and antimicrobial activity of food packaging materials are among the most attractive parameters in modern food industries. In order to develop biodegradable poly-lactic acid (PLA) film to antibacterial nanocomposites, different concentration of Zataria multiflora Bioss. essential oil (ZME), propolis ethanolic extract (PEE) and cellulose nanofiber (CNF) were incorporated to the polymer by solvent casting method. The resulting films were characterized by mechanical and physical tests and their antimicrobial application was evaluated in-vitro against four common foodborne pathogens and in vacuum-packed cooked sausages during refrigerated storage. Mechanical examination revealed that addition of ZME and PEE made films more flexible and incorporation of CNF improved almost all mechanical parameters tested. Moreover, according to physical analysis, incorporation of 0.5% v/v ZME to the composite primary solutions improved water vapor permeability of the resulting films. Almost all of the active films were effective against the tested bacteria except for PLA/PEE films, and maximum antibacterial effects recorded for the films containing both ZME and PEE. Based on the microbiological and sensory evaluation of the sausages, all of the PLA/1%ZME/PEE composites increased the shelf life to >40days. The results indicate that incorporation of natural antimicrobial substances such as ZME and PEE to packaging material could be an interesting approach in development of active packaging material without significant negative effect on polymer technical properties.