Addition Of Nisin Research Articles

Influence of melt processing on biodegradable nisin‐PBAT films intended for active food packaging applications

ABSTRACTBiodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) films incorporated with different levels of the antimicrobial peptide nisin were developed by melt processing. Structural, morphological, thermal, mechanical, and antimicrobial properties of the films were determined. The X‐ray diffraction patterns exhibited decreasing levels of intensity at 2θ values as the concentration of nisin increased. Scanning electron microscopy showed a heterogeneous morphology when higher amounts of nisin were incorporated. The antimicrobial films tested presented no significant differences in the melting temperature (123–125°C), and the crystallization temperature ranged from 69 to 75°C. The addition of nisin caused no significant modification in tensile strength values. However, results of Young's modulus and deformation at break differed significantly among samples. Active films demonstrated inhibition against the Gram‐positive bacterium Listeria monocytogenes. These results demonstrated that PBAT/nisin films produced by melt processing present a great potential for use as active food packaging materials aiming enhanced food safety. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43212.

Effect of Nisin and Thermal Treatments on the Heat Resistance of Clostridium sporogenes Spores

The aim of this research was to evaluate the effect of thermal treatments (isothermal or nonisothermal) combined with nisin, a natural antimicrobial, on the survival and recovery of Clostridium sporogenes spores. The addition of nisin to the heating medium at concentrations up to 0.1 mg liter-1 did not reduce the heat resistance of C. sporogenes. Without a thermal treatment, nisin added at concentrations up to 0.1 mg liter-1 did not reduce the viable counts of C. sporogenes when added to the recovery medium, but inactivation of more than 4 log cycles was achieved after only 3 s at 100°C. At 100°C, the time needed to reduce viable counts by more than 3 log cycles was nine times shorter when 0.01 mg liter-1 nisin was added to the recovery medium than without it. The heat resistance values calculated under isothermal conditions were used to predict the survival in the nonisothermal experiments, and the predicted values accurately fit the experimental data. The combination of nisin with a thermal treatment can help control C. sporogenes.

Influence of Nisin and Lauryl Arginine Ester Against Some Foodborne Pathogens in Recombined Feta and Processed Spread Cheese

The aim of this study was to evaluate the impact of nisin with lauryl arginine ester (LAE) or their combination by 1: 3 (w/w) on cheese preservation. The study was carried out against the most common foodborne pathogens in recombined feta cheese (RFC) and processed cheese spread (PCS). Combination of nisin with LAE has higher synergistic preservative effect on different widespread foodborne pathogens such as Bacillus subtilis, Clostridium sporogenes and Escherichia coli compared with individual one. The most sensitive strain was E. coli with an effective minimal inhibition concentration (MIC) of 400 ppm, whereas the former spore-forming bacterial strains were totally inhibited using 700 ppm from the combination, respectively. Synergistic combination blend was added by its recommended MIC (700 ppm) in the manufacture of both RFC and PCS. The results indicated that it is efficient enough to inhibit the growth of the most common foodborne pathogens in cheese after their storage for 7 days (RFC) and 30 days (PCS). Practical Applications Inhibiting the foodborne pathogens by the addition of lauryl arginine ester (LAE) and nisin together by 1: 3 (w/w) increased the cheese quality. However, the possibility of contamination of traditional cheese during the preservation in terms of food safety can be controlled by the addition of the two mentioned additives (i.e., LAE and nisin) and can be manufacture and distribute in the dairy industries.

Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: Application in the control of Listeria monocytogenes in fresh Minas-type goat cheese.

Listeria monocytogenes is a pathogen frequently found in dairy products. Its control in fresh cheeses is difficult, due to the psychrotrophic properties and salt tolerance. Bacteriocinogenic lactic acid bacteria (LAB) with proven in vitro antilisterial activity can be an innovative technological approach but their application needs to be evaluated by means of in situ tests. In this study, a novel bacteriocinogenic Lactococcus lactis strain ( Lc . lactis DF4Mi), isolated from raw goat milk, was tested for control of growth of L. monocytogenes in artificially contaminated fresh Minas type goat cheese during storage under refrigeration. A bacteriostatic effect was achieved, and counts after 10 days were 3 log lower than in control cheeses with no added LAB. However, this effect did not differ significantly from that obtained with a non-bacteriocinogenic Lc. lactis strain. Addition of nisin (12.5 mg/kg) caused a rapid decrease in the number of viable L. monocytogenes in the cheeses, suggesting that further studies with the purified bacteriocin DF4Mi may open new possibilities for this strain as biopreservative in dairy products.

The polyamine N-acetyltransferase-like enzyme PmvE plays a role in the virulence of Enterococcus faecalis.

We previously showed that the mutant strain of Enterococcus faecalis lacking the transcriptional regulator SlyA is more virulent than the parental strain. We hypothesized that this phenotype was due to overexpression of the second gene of the slyA operon, ef_3001, renamed pmvE (for polyamine metabolism and virulence of E. faecalis). PmvE shares strong homologies with N(1)-spermidine/spermine acetyltransferase enzymes involved in the metabolism of polyamines. In this study, we used an E. faecalis strain carrying the recombinant plasmid pMSP3535-pmvE (V19/p3535-pmvE), which allows the induction of pmvE by addition of nisin. Thereby, we showed that the overexpression of PmvE increased the virulence of E. faecalis in the Galleria mellonella infection model, as well as the persistence within peritoneal macrophages. We were also able to show a direct interaction between the His-tagged recombinant PmvE (rPmvE) protein and putrescine by the surface plasmon resonance (SPR) technique on a Biacore instrument. Moreover, biochemical assays showed that PmvE possesses an N-acetyltransferase activity toward polyamine substrates. Our results suggest that PmvE contributes to the virulence of E. faecalis, likely through its involvement in the polyamine metabolism.

Polypropylene/Montmorillonite Nanocomposites Containing Nisin as Antimicrobial Food Packaging

Antimicrobial nanocomposites prepared with polypropylene, montmorillonite, and nisin were developed as food packaging material. Nisin was incorporated at 1, 2.5, and 5 % (w/w) and the characterization included antimicrobial, mechanical, thermal, barrier, and structural properties. Composite films inhibited the Gram-positive bacteria Listeria monocytogenes, Staphylococcus aureus, and Clostridium perfringens when tested on skimmed milk agar plates. Antimicrobial activity was released in food simulants after contact with the nanocomposites, increasing until 48 h in solutions containing the surfactant Tween 20 or acetic acid. The addition of nisin caused no significant modification in deformation at break values as compared with control films. However, results of tensile strength and Young modulus differed significantly among samples. The higher value for Young modulus was observed for films with 5 % nisin. Water vapor barrier properties were not significantly different among control and antimicrobial films, whereas oxygen permeability was higher for nanocomposites containing nisin. The nanocomposites tested had no significant differences in the melting temperature (165 to 167 °C), and the crystallization temperature ranged from 121 to 129 °C, with lower values for films containing 5 % nisin. Scanning electron microscopy showed that nanocomposites containing 1 and 2.5 % nisin present similar homogeneity to that of control films. Some film properties were affected after nisin incorporation in polypropylene/montmorillonite matrix but active antimicrobial films were obtained, showing suitable behavior as a food packaging material.

High-pressure and temperature effects on the inactivation of Bacillus amyloliquefaciens, alkaline phosphatase and storage stability of conjugated linoleic acid in milk

Milk rich in conjugated linoleic acid (CLA, 42 ± 3 mg g− 1 fat) was used to evaluate the impact of high-pressure sterilization (HPS). The pressure, temperature and time needed to reduce 7-log of Bacillus amyloliquefaciens endospores were determined in the presence of nisin (4–64 mg L− 1). In addition, the inactivation of alkaline phosphatase was evaluated. After HPS treatment, the remaining CLA and formation of hydroperoxides were monitored during storage up to 60 d at 25 °C. The addition of nisin (≥ 16 mg L− 1) to milk significantly enhanced the inactivation of B. amyloliquefaciens (7-log reduction) after treatment at 600 MPa, 120 °C and 5 min of holding time. These conditions were selected to evaluate the impact of HPS on the CLA retention and hydroperoxides formation. Milk with the addition of nisin and treated with HPS delivered higher retention of CLA and a lower concentration of hydroperoxides compared with the UHT equivalent process (125 °C/15 s and 135 °C/10 s).

Nisin‐loaded alginate‐high methoxy pectin microparticles: preparation and physicochemical characterisation

SummaryThe bacteriocin nisin has been extensively used as potential natural preservative in the food industry. However, antimicrobial activity of nisin due to its binding with food components and inactivation by enzymatic degradation is reduced when it is applied in food. Encapsulation of nisin is an efficient approach to overcome the problems related to the direct application of this antimicrobial peptide in foods. In this study, nisin was encapsulated in alginate‐high methoxy pectin (HMP) microparticles, and its release studies were performed in water to determine the diffusion and the kinetic behaviour of the matrix. Results showed that the nisin content had a significant influence on encapsulation efficiency (EE), loading capacity (LC) and microparticles size. The values of EE, LC and particle mean diameter were about 47–54%, 16–21% and 57–131 μm, respectively. The nisin‐loaded microparticles showed nearly spherical structure with fold on the surface, as displayed by scanning electron micrograph. Interaction between alginate and HMP was confirmed by the changes in the intensity and wave number of the stretching vibrations of the hydroxyl and carboxyl groups in alginate‐HMP microparticles FTIR spectra. Furthermore, the addition of nisin resulted in a markedly increase in intensity of carboxylic peak at 1620 cm−1, indicating the presence of nisin inside of the microparticles. The in vitro nisin release from these microparticles followed a sustained release profile consistent with a Fickian diffusion mechanism.

Inactivation of Escherichia coli and Staphyloccocus aureus in Litchi Juice by Dimethyl Dicarbonate (DMDC) Combined With Nisin

<p>Inactivation of Gram-negative <em>Escherichia coli</em> and Gram-positive <em>Staphyloccocus aureus</em> in litchi juice by DMDC combined with nisin was individually investigated. A 1.66 log cycles reduction of<em> E. coli </em>and 2.03 log cycles reduction of <em>S. aureus </em>in litchi juice (pH 4.5) added without nisin was achieved as exposed to 150 mg/l DMDC at 30 °C for 1 h, and the inactivation rate of <em>E. coli </em>and <em>S. aureus</em> during initial 1 h was far greater than during the remaining 5 h. As exposed to 150 mg/l DMDC at 30 °C for 1 h, the inactivation of <em>E. coli</em> and <em>S. aureus</em> in the litchi juice showed a trend toward increase with increasing of nisin addition level in the range from 0 to 200 IU/ml. Moreover, DMDC and nisin exhibited a synergistic effect on the inactivation of <em>E. coli</em> and <em>S. aureus</em> in litchi juice, and the inactivation of<em> E. coli</em> and <em>S. aureus</em> in the litchi juice also depends on the temperature of litchi juice, pH value of litchi juice and DMDC concentration when treated with DMDC and nisin. In addition, <em>E. coli</em> showed higher resistance to nisin as comparing with <em>S. aureus</em>. After <em>E. coli</em> and <em>S. aureus</em> in the litchi juice of pH 4.0 were individually treated with 150 mg/l DMDC combined with 200 IU/ml nisin at 30 °C for 1 h, a complete inactivation of <em>S. aureus</em> (6.59 log cycles) was achieved, but only 3.52 log cycles reduction of <em>E. coli</em> was observed.</p>

Injury and Viability Loss of Escherichia coli O157:H7, Salmonella, Listeria Monocytogenes and Aerobic Mesophilic Bacteria in Apple Juice and Cider Amended with Nisin-Edta

For health reasons, people are consuming fresh juices or minimally processed fruit and vegetable juices, thereby, exposing themselves to the risk of foodborne illness if such juices are contaminated with bacteria pathogens. Behavior of aerobic mesophilic bacteria, Escherichia coli O157:H7, L. monocytogenes and Salmonella cells at 104 CFU/ml in apple cider (pH 3.9) and apple juice (pH 3.6), amended with nisin (500 IU/ml)+ethylene diaminetetraacetic acid (EDTA, 0.02 M) combination treatment and storage at 5°C and 10°C for 10 days as well as 22oC for 16 h was investigated. Populations of aerobic mesophilic bacteria increased in untreated apple cider stored at 5°C and 10°C for 10 days while E. coli O157:H7, L. monocytogenes and Salmonella slightly declined. A slight increase for E. coli O157:H7, L. monocytogenes and Salmonella in juices stored at room temperature (22°C) was observed. Treatment of juices with nisin+EDTA led to higher inactivation of bacterial populations including inoculated populations of E. coli O157:H7, L. monocytogenes and Salmonella. The surviving populations determined within 10 to 30 min of treatment include 18% of injured cells. And leakage of UV- absorbing materials were higher in samples containing the injured bacteria. The injured populations did not recover during storage at 5 or 22°C. Waiting up to 4 h before refrigeration of treated samples and leaving treated refrigerated samples at room temperature for up to 4 h did not cause significant changes in microbial populations. Addition of nisin+EDTA combination in unpasteurized apple cider or apple juice as a natural antimicrobial will improve the microbial safety of the juices. However, treatment of juices with nisin+EDTA combination is still subject to regulatory approval by the FDA.

Effect of Environmental Factors on Production of Hyaluronic Acid by Streptococcus zooepidemicus

The effects of various environmental factors on the production of hyaluronic acid (HA) by Streptococcus zooepidemicus BCRC15414, the quantitation of HA by HPLC and morphology of the strain were examined. The cell growth was enhanced by aeration and agitation, but the influence of aeration was significantly higher. Agitation enhanced the HA production, but aeration has no beneficial effect for the HA production. Aeration and agitation significantly increased the kLa values; however, the kLa is not a determined factor for the HA production. A two-stage anoxic (static)-aerobic sequential culture, which is static for 24 h followed by aeration at 2 L/min, led to superior results both in biomass and HA production at the end of cultivation. The optimal initial glucose concentrations was about 20g/L, which led to highest HA production (0.51 g/L) after 24 h of cultivation in the two-stage anoxic (static)-aerobic sequential culture. The average molecular weight (Mw) of HA produced was 3.0×103 kDa, which was not affected by the glucose concentration used. Meanwhile, the addition of nisin enhanced the glucose consumption, biomass and HA production. Substrate inhibition on HA production was observed for S. zooepidemicus BCRC15414 when the initial glucose concentration was above the optimal value ( ＞ 20 g/L); no substrate inhibition on cell growth was observed. In the quantitation of HA, HA concentration analyzed by HPLC method was more accurate than that analyzed by carbazole method. Distinctive differences of morphologies were observed for the low and high HA producing strains, which provides a simple and important tool that enable one to screen and identify the ability of a strain to produce high titer of HA.

Antimicrobial films and coatings for inactivation of Listeria innocua on ready-to-eat deli turkey meat

Edible antimicrobial coating solutions incorporating chitosan, lauric arginate ester (LAE) and nisin were developed to reduce foodborne pathogen contamination on ready-to-eat (RTE) meats. RTE deli meat samples were directly coated with the solutions, or treated with solution-coated polylactic acid (PLA) films. The antimicrobial efficacy of the coatings and films against Listeria innocua inoculated onto the surface of RTE meat samples was investigated. Antimicrobial coatings with 1.94 mg/cm2 of chitosan and 0.388 mg/cm2 of LAE reduced L. innocua by ca. 4.5 log CFU/cm2. Nisin (486 IU/cm2) showed less effectiveness than LAE (0.388 mg/cm2) and addition of nisin to the antimicrobial coatings or films containing LAE (0.388 mg/cm2) did not enhance the total antimicrobial effectiveness. Combining antimicrobial coatings or films with flash pasteurization (FP), which uses short burst of steam under pressure, further reduced L. innocua, achieving over a 5 log reduction. There was no significant difference in the effectiveness of antimicrobial films versus the coatings (p > 0.05). These data show the potential use of antimicrobial packaging alone, or in combination with FP, in preventing foodborne illness due to post-processing contamination of RTE meat products.

Antimicrobial activity of nisin, thymol, carvacrol and cymene against growth of Candida lusitaniae

Yeasts are tolerant to acid pH values, are able to grow in anaerobic media and have minimum nutrition requirements. These capabilities enable them to survive and even grow in foods prepared from acid fruits or vegetables. Among yeasts, Candida is one of the genus most frequently isolated from fruit juices. Bacteriocins and essential oils from spices and aromatic herbs are an alternative to preservatives and other technological treatments and have the advantage that their natural origins do not lead to consumer rejection. However, before the food industry uses them on a large scale, it is necessary to know their effects on microorganisms. The objective of this research was to study the effect of different concentrations of nisin, thymol, carvacrol and cymene on the growth of Candida lusitaniae in pH 5 broth at 25 ℃, and their potential uses as food preservatives. The addition of nisin at the concentrations tested (up to 3 µmol L(-1)) did not affect the yeast growth. Thymol, carvacrol and cymene completely inhibited the yeast growth at concentrations over 1 mM for at least 21 days at 25 ℃. Below this concentration, inhibitions on yeast growth were observed at increasing concentrations. The effect of thymol was also proved in tomato juice. This study indicates the potential use of essential oils for preservation of minimally processed foods.

Preservation of Manzanilla Aloreña cracked green table olives by high hydrostatic pressure treatments singly or in combination with natural antimicrobials

High hydrostatic pressure (HHP) treatments (singly or in combination with natural antimicrobials) were tested for stabilization of Manzanilla Aloreña seasoned olives stored at 25 °C. HHP (5 min) was highly effective on yeast populations at 300 MPa or higher. No viable yeasts were detected in samples treated at 400 MPa for up to three months. Low levels of endospore-forming bacteria were always detected after HHP treatments. Addition of nisin to the brines reduced bacterial counts by 1.4 log cycles but it had no effect on yeasts when tested singly or in combination with HHP treatment (400 MPa, 5 min). Thyme oil had almost no effect on yeast concentrations, but rosemary oil reduced yeast viable counts progressively during storage. Essential oils in combination with HHP (400 MPa, 5 min) significantly (p < 0.05) reduced the concentrations of aerobic mesophilic bacteria. Low-salt brined olives purged with N2 or supplemented with ascorbic acid and then pressurized for 5 min at 450 or 550 MPa were preserved for up to 5 months without spoilage, suggesting that the NaCl content in brines of packed Manzanilla Aloreña table olives could be reduced considerably by application of HHP as a stabilization treatment.

Inhibitory effect of combinations of caprylic acid and nisin on Listeria monocytogenes in queso fresco

Queso fresco (QF), a fresh Hispanic cheese has been linked to outbreaks and recalls caused by Listeria contamination. The use antimicrobial treatments may be a potential solution. The goal of this research was to test the addition of nisin (N), caprylic acid (CA) and trans-cinnamaldehyde (CN) as anti-listerial ingredients in QF. QF batches were inoculated with approx. 104 CFU/g of 5- or 6-strain mixtures of Listeria monocytogenes and treated with antimicrobials. Samples were stored at 4 °C for three weeks and Listeria counts were determined by plating on PALCAM agar. The impact on the QF's natural indicator microorganisms was also assessed during refrigerated storage. All N and CA combinations (≥0.4 g/kg each) were effective against L. monocytogenes and reduced the final counts by at least 3 log CFU/g after 20 days of storage compared to controls. The levels of most strain mixtures were reduced immediately after treatment and their numbers remained below 103 CFU/g during storage. CN (1.2 g/kg) was bacteriostatic against L. monocytogenes, but it did not reduce initial counts. The addition of CN to the combination of N and CA did not enhance their antimicrobial effect. Results indicated that combinations of N and CA could control L. monocytogenes in QF with little impact on the natural flora of the cheese, providing a solution to control post processing L. monocytogenes contamination of QF.

Improvement in Shelf Life and Safety of Pasteurized Palm Sap (Borassus flabellifer Linn.) by the Addition of Nisin

AbstractThe objective of this study was to improve the quality and safety of pasteurized palm sap by the addition of various concentrations of nisin. The pasteurization condition was 75C for 10 min as considered from no growth of pathogens was detected while the concentrations of nisin in the range of 0–40 IU/mL were selected for addition in palm sap as considered from sensory evaluation. The initial pH of pasteurized palm sap was 6.6 and the addition of nisin caused a decrease in the pH to 6.2, 6.0, 5.8 and 5.6 for the samples added 10, 20, 30 and 40 IU/mL, respectively. The initial polyphenol oxidase activity decreased by approximately 55 and 76% for the sample without nisin added and the sample added 40 IU/mL nisin, respectively, from the original value measured in fresh palm sap while the initial invertase activity was not affected by nisin. During storage, the loss of sucrose, polyphenol content, DPPH‐RSA and the increment in browning intensity were minimized by nisin treatment, particularly at 30–40 IU/mL. The combination of pasteurization with the addition of nisin (30 IU/mL) and low temperature storage could preserve palm sap for 10 weeks whereas the control sample was spoiled within 2 weeks.Practical ApplicationsThe sale of pasteurized palm sap is a common practice in Thailand and its consumption has increased over the past years. However, pasteurized palm sap has a short shelf life (approximately 1–2 weeks). In order to control the growth of spoilage microorganisms, the use of natural antimicrobial preservatives has been preferred in the food industry. For this purpose, nisin was preferred in this study. Although there are many reports on the use of nisin to prolong the shelf life of food, research on the utilization of nisin in palm sap is limited. According to the results, the addition of nisin could reduce the pasteurization temperature and time. In addition, the use of nisin (30 IU/mL) significantly reduced spoilage microorganism counts and extended the refrigerated shelf life of pasteurized palm sap for at least 10 weeks. Therefore, the safety of pasteurized palm sap during storage could be improved by the addition of nisin. This result may be a practical application for the producer because of the short shelf life of this product.

Combined Effect of Dimethyl Dicarbonate (DMDC) and Nisin on Indigenous Microorganisms of Litchi Juice and its Microbial shelf life

The individual and combined influences of dimethyl dicarbonate (DMDC) and nisin (200 IU/mL) at mild heat on the inactivation of indigenous microorganisms in litchi juice, including bacteria, molds and yeasts (M&Y), were investigated. The fresh litchi juice with or without nisin were exposed to 250 mg/L DMDC at 30, 40, or 45 °C for 0.5, 1, 2, 3, 4, or 6 h. A complete inactivation of M&Y in the litchi juice with or without nisin was achieved as exposed to 250 mg/L DMDC at 30, 40, or 45 °C for 0.5 h. The bacteria, especially Bacillus sp. and Leuconstoc mesenteroides showed higher resistance than M&Y in the litchi juice. Bacillus sp. and Leuconstoc mesenteroides in the litchi juice was not completely inactivated by 250 mg/L DMDC at 30, 40, or 45 °C. However, nisin addition can enhanced the inactivation of these bacteria by DMDC, and nisin and DMDC also showed a synergistic effect on the inactivation of bacteria. M&Y and bacteria were not detected in the litchi juice added with 200 IU/mL nisin as exposed to 250 mg/L DMDC at 45 °C for 3 h. In addition, microbial shelf life of the litchi juice during storage at 4 °C also was evaluated as treated by 250 mg/L DMDC or combination with nisin at 45 °C for 3 h.

Development of Antimicrobial Coatings for Improving the Microbiological Safety and Quality of Shell Eggs

This study was conducted to develop antimicrobial coatings to decontaminate and prevent cross-contamination of shell eggs. Egg shells were inoculated with nalidixic acid-resistant Salmonella enterica Enteritidis strains OB030832, OB040159, and C405 and treated with antimicrobial coatings. Polylactic acid served as a nonedible polymer, and chitosan served as an edible polymer carrier of natural antimicrobials, including nisin, allyl isothiocyanate (AIT), lauric arginate ester (LAE), and organic acids. Increases of AIT concentrations or addition of nisin to AIT in either the polylactic acid or chitosan coating solutions resulted in greater reductions of Salmonella. Chitosan coatings with 0.1, 0.5, and 1.0% LAE reduced Salmonella by 1.7, 2.5, and 5.2 log CFU/cm(2), respectively. Shell eggs treated with 1.0 and 0.5% LAE in chitosan coatings had nondetectable Salmonella cells (< 0.5 log CFU/cm(2)) after 3 and 7 days of storage at 7°C, respectively, and no outgrowth was observed up to 28 days. Coating treatments significantly reduced weight loss of shell eggs during 12 weeks of storage at 7 or 4°C. This study demonstrates an alternative and effective intervention technology for decontaminating shell eggs and provides an alternative approach to reduce possible recalls and outbreaks associated with pathogen contamination on shell eggs and in egg products.

Efficient electroporation of liposomes doped with pore stabilizing nisin

Context: Liposomes have a long history as passive and active drug carriers. Recently, a few methods have been realized to control the release from liposomes, including heating, ultrasound and laser.Objective: We report on a new approach to drive release from liposomes using electric fields.Materials and methods: Liposomes were manufactured containing a high concentration of (quenched) 5-6 carboxyfluorescein dye. Nisin, a well-known amphiphilic peptide lantibiotic that works by stabilizing pores formed in cell membranes, was mixed in solution inside or outside the liposomes. The liposomes were then electroporated using a range of voltages, and assayed for increases in fluorescence due to release of dye. Release was measured against positive and negative controls, with positive control release driven by a strong detergent.Results: Our results demonstrate that the addition of nisin significantly reduces the electric field required to release the contents of liposomes, from 2000 V/m to approximately 200 V/m. This result proves that, in principle, electroporation (EP) of liposomes doped with small amounts of amphiphilic pore stabilizing peptides may be a practical means to drive release of liposomal contents in vivo.Conclusion: Drug delivery from liposomes doped with amphiphilic peptides using EP is feasible. This technique could be developed into a potent adjuvant to tumor ablation using irreversible EP.

In-vitro effect of nisin onStaphylococcus aureuspool isolates from Minas traditional cheeses from Campo das Vertentes-MG

Minas traditional cheeses currently have a prominent role in the scientific depending on their social and economic importance to the country legally. Although the cheese can be marketed within the state, is notorious its presence outside of Minas Gerais. Because it is made with raw milk, the cheese has a risk for consumers to be potential carrier of pathogens such as Listeria, Salmonella and Staphylococcus aureus . The use of raw milk implies the need for studies to significantly decrease their contamination by S. aureus . Studies have shown that the addition of nisin to cheese manufacturing process can significantly reduce the contamination. The aim of this study was to evaluate the effect of Nisin on pool S. aureus isolates from traditional cheeses of Campo das Vertentes. Four levels (100, 200, 400 and 500 IU. mL -1 ) of the commercial preparation Nisaplin ® in autoclaved reconstituted skim milk at 10%. The analysis of S. aureus were made using 3M Petrifilm at zero; 3, 5, 8, 10, 12, 16, 24, 36, 48, 72, and 96 of incubation. There was no significant difference (p > 0.05) between control and doses of 200 IU mL -1 . However differences were observed between the other doses (p <0.05) in the two mentioned and also among themselves. The results of this study confirm those already made elsewhere showing that nisin can be effective in reducing counts of S. aureus in cheeses made with raw milk.