Activity Of Nisin Research Articles

Enhancement of the Antibiofilm Activity of Nisin against Listeria monocytogenes Using Food Plant Extracts.

Listeria monocytogenes is a foodborne pathogen exhibiting a high mortality rate. In addition to the robust tolerance to environmental stress, the ability of L. monocytogenes to develop biofilms increases the risk of contaminating food processing facilities and ultimately foods. This study aims to develop a synergistic approach to better control Listeria biofilms using nisin, the only bacteriocin approved as a food preservative, in combination with gallic-acid-rich food plant extracts. Biofilm assays in the presence of nisin and gallic acid or its derivatives revealed that gallic acid significantly decreased the level of biofilm formation in L. monocytogenes, whereas ethyl gallate, propyl gallate, and lauryl gallate enhanced biofilm production. As gallic acid is widely distributed in plants, we examined whether extracts from gallic-acid-rich food plants, such as clove, chestnut, oregano, and sage, may generate similar antibiofilm effects. Remarkably, sage extracts enhanced the antibiofilm activity of nisin against L. monocytogenes; however, the other tested extracts increased biofilm formation, particularly at high concentrations. Moreover, sage extracts and nisin combinations significantly reduced the biofilm formation of L. monocytogenes on stainless steel. Sage is a common food spice and has various beneficial health effects, including antioxidation and anti-cancer properties. The findings in this study demonstrate that sage extracts can be potentially combined with nisin to prevent biofilm production in L. monocytogenes.

Anti-virulence activity of dihydrocuminyl aldehyde and nisin against spoilage bacterium Pseudomonas aeruginosa XZ01

The aim of this study was to investigate the anti-virulence potential and mechanism of Perilla frutescens-derived dihydrocuminyl aldehyde (DCA) against the spoilage bacterium Pseudomonas aeruginosa XZ01 derived from rotten chicken meat using transcriptome sequencing and 1H NMR-based metabolomics. At concentrations ranging from 1 to 3 μL/mL, DCA notably reduced the production of protease, elastase, pyocyanin, and rhamnolipid. The synergistic effects of DCA and nisin on biofilm formation and their ability to disrupt the preformed biofilms of P. aeruginosa XZ01 were also investigated through scanning electron microscopy and confocal laser scanning microscopy. Mechanistically, the potential of DCA to down-regulate quorum sensing (QS)-related genes, boost membrane permeability, and suppress the efflux system and outer membrane porin facilitated the anti-virulence effects and increased susceptibility of biofilm cells to nisin. DCA treatment also induced energy metabolism disorder, inhibited antioxidant enzymes, and intensified oxidative stress, leading to protein metabolism and DNA synthesis disorder, and ultimately attenuated virulence and spoilage efficiency of P. aeruginosa XZ01. Our results indicate that DCA has the potential to function as an anti-virulence agent to defend against foodborne pathogens.

The Effect of Nisin and Chloramphenicol Combinationon Staphylococcus aureus ATCC 6538 Biofilm Structure

Nowadays, due to the rapid spread of antibiotic resistance and the difficulty of discovering new antimicrobial agents, the reuse and combinational strategies of old antibiotics have come to the fore. In this study, we investigated the combinational efficacy of nisin and chloramphenicol against the ATCC 6538 strain of Staphylococcus aureus. The MIC values of nisin and chloramphenicol were >64 and 32 µg/mL, respectively. The checkerboard assay was carried out for the inspection of synergism between nisin and chloramphenicol. Furthermore, the crystal violet assay was employed to assess antibiofilm effects. Additionally, the expressions of various virulence genes (agrA, spa, icaA and saeR) were investigated using the colony biofilm assay and qRT-PCR methods. In combination application, MIC values of nisin and chloramphenicol was decreased. In addition, biofilm formation was decreased.It was shown that the expression level of the agrA gene decreased compared to the control in the nisin, chloramphenicol and combinational applications. The expression levels of other genes were increased compared to the control. The results showed that the activities of nisin and chloramphenicol combinations had synergistic and antibiofilm activity. This study sheds light on the combinatorial use of older antibiotics.

NISIN and gilaburu (Viburnum opulus L.) combination is a cost-effective way to control foodborne Staphylococcus aureus

This study aims to elucidate the inhibitory activity of nisin alone or in combination with gilaburu ( Viburnum opulus L.) against the foodborne Staphylococcus aureus . The effect of nisin and gilaburu on the growth of S. aureus was investigated under different pH (5–7) and salt concentrations (NaCl, 0.5–4.5% w/v) at 30 °C. Nisin exhibited the best antibacterial activity at pH 5 with a minimum inhibitory concentration (MIC) of 25 μg/mL, while its MIC was 50 μg/mL in all salt concentrations when the pH was kept constant at pH 7. The MIC of gilaburu was found to be 50% in all conditions studied. The minimum bactericidal concentrations (MBC) of nisin and gilaburu were 100 μg/mL and >50%, respectively. Changes in pH and salt concentrations did not affect MBC. According to checkboard assay results, a synergy was found between gilaburu and nisin (FIC = 0.25) for both 2.5% and 4.5% w/v salt concentrations at pH 5. The synergistic interaction between nisin and gilaburu was also studied using an agar disk diffusion assay where nisin concentration was kept constant at 3.125 μg/ml, while gilaburu concentration varied between 3.125 and 100%. The positive effect of gilaburu on nisin activity was further confirmed by time-kill assay, flow cytometry, and measurement of relative TTC dehydrogenase activity and conductivity as well as DNA and protein leakage. In conclusion, nisin combined with gilaburu exerted the same inhibitory effect on S. aureus at a concentration approximately 8 times lower than that of MIC of nisin alone (25 μg/mL). This study shows the potential use of nisin and gilaburu in combination to control S. aureus in food. • S. aureus can be controlled with 8 times less nisin in the presence of gilaburu. • Synergy was found between gilaburu and nisin (FIC = 0.25) according to checkboard assay. • Synergistic effect of nisin and gilaburu on S. aureus was proven by different methods. • Nisin and gilaburu combination is an effective strategy to control S. aureus in food.

Discovery of the Potentiator of the Pore-Forming Ability of Lantibiotic Nisin: Perspectives for Anticancer Therapy.

This study was focused on the action of lantibiotic nisin on the phospholipid membranes. Nisin did not produce ion-permeable pores in the membranes composed of DOPC or DOPE. The introduction of DOPS into bilayer lipid composition led to a decrease in the threshold detergent concentration of nisin. An addition of nisin to DOPG- and TOCL-enriched bilayers caused the formation of well-defined ion pores of various conductances. The transmembrane macroscopic current increased with the second power of the lantibiotic aqueous concentration, suggesting that the dimer of nisin was at least involved in the formation of conductive subunit. The pore-forming ability of lantibiotic decreased in the series: DOPC/TOCL ≈ DOPE/TOCL >> DOPC/DOPG ≥ DOPE/DOPG. The preferential interaction of nisin to cardiolipin-enriched bilayers might explain its antitumor activity by pore-formation in mitochondrial membranes. Small natural molecules, phloretin and capsaicin, were found to potentiate the membrane activity of nisin in the TOCL-containing membranes. The effect was referred to as changes in the membrane boundary potential at the adsorption of small molecules. We concluded that the compounds diminishing the membrane boundary potential should be considered as the potentiator of the nisin pore-forming ability that can be used to develop innovative formulations for anticancer therapy.

Bioengineered Nisin A Derivatives Display Enhanced Activity against Clinical Neonatal Pathogens.

Neonatal infection is a significant cause of mortality and morbidity in infants. The global incidence of multi-drug resistance continues to rise among neonatal pathogens, indicating a need for alternative treatment strategies. Nisin is an antimicrobial peptide that exhibits broad-spectrum activity against a wide variety of clinical pathogens and can be used in combination with antibiotics to improve their effectiveness. This study examined the activity of nisin and bioengineered derivatives against multi-drug resistant Streptococcus agalactiae and Staphylococcus capitis isolates and investigated the potential synergy between nisin peptides and selected antibiotics. Whole genome sequence analysis of the strains revealed the presence of multi-drug resistant determinants, e.g., macrolide, tetracycline, β-lactam, aminoglycoside, while the S. agalactiae strains all possessed both nsr and nsrFP genes and the S. capitis strains were found to encode the nsr gene alone. Deferred antagonism assays demonstrated that nisin PV had improved antimicrobial activity against all strains tested (n = 10). The enhanced specific activity of this peptide was confirmed using minimum inhibitory concentrations (MIC) (0-4-fold lower MIC for nisin PV) and broth-based survival assays. Combinations of nisin peptides with antibiotics were assessed for enhanced antimicrobial activity using growth and time-kill assays and revealed a more effective nisin PV/ampicillin combination against one S. capitis strain while a nisin A/erythromycin combination displayed a synergistic effect against one S. agalactiae strain. The findings of this study suggest that nisin derivatives alone and in combination with antibiotics have potential as alternative antimicrobial strategies to target neonatal pathogens.

Effects of Individual and Combined Fermentation Factors on Antimicrobial Activity of Nisin by Lactococcus lactis ATCC 11454.

There is an increasing demand for natural food preservatives due to consumers' concern on the negative effects of chemical preservatives in food products. Nisin (bacteriocin) is an effective food biopreservative that has been approved globally. However, its low yield proves to be a limiting factor and must be addressed to meet the increasingly high demand from the food industry. The present work thus investigated the effects of individual and combined fermentation factors on Lactococcus lactis ATCC 11454 growth and nisin activity using the one-factor-at-a-time (OFAT) method. The level of each factor that gave the highest nisin production was then selected and combined to further improve its activity. The best combined conditions for highest cell growth and nisin activity were 30°C, pH 6.0, and mild agitation with the addition of 1.0% w/v glucose, 1.0% w/v skim milk, and 0.5% v/v Tween 20. This increased nisin production by 22.7% as compared to control (basic condition). The present work provided critical information on the relationship between fermentation conditions, growth, and nisin activity of L. lactis ATCC 11454 that could be explored to understand the potential and limitation of the strain. This fermentation strategy can also serve as a benchmark to further enhance the production of bacteriocin or other biopreservative compounds.

Prevalence of Listeria monocytogenes in ready-to-eat foods, and growth boundary modeling of the selected strains in broth as a function of temperature, salt and nisin

ABSTRACT The objectives of this study were to determine the prevalence of Listeria monocytogenes in ready-to-eat (RTE) foods, and the growth boundaries of two strains of L. monocytogenes isolated from RTE foods and one ATCC7644 strain under different temperature (4, 20, and 37°C), salt (0, 1, 2, 3, and 4% w/v), and nisin (0, 50, 100, 200, and 400 µg/mL) levels with different inoculum sizes (3, 4, 5, and 6 log10 CFU/mL). One hundred thirty-three retail RTE foods were examined and a total of 39 isolates were identified. The positive Listeria spp. and L. monocytogenes samples were 29.3% and 12.8%, respectively. Dairy and fruit-based RTE foods were L. monocytogenes negative whereas seafood-based (26.7%), meat-based (19.4%), poultry-based (16%), and vegetable-based (10%) RTE foods contained L. monocytogenes. It was shown that nisin was more effective than NaCl to avoid growth. Moreover, protective effect of NaCl on nisin activity was observed. As inoculum size increased probability of growth also increased. Suppressing the growth by using temperature, NaCl and nisin was more difficult in RTE-isolates strains (strains 120 and 137) than that of ATCC7644 strain. A mathematical model based on logistic regression could be used to determine growth limits of L. monocytogenes strains with a concordance of > 91%.

Bacterial Cellulose Membranes as Carriers for Nisin: Incorporation, Antimicrobial Activity, Cytotoxicity and Morphology.

Based on the previous study, in which nisin and bacterial cellulose were utilized, this new experiment loads nisin into bacterial cellulose (N–BC) and evaluates the morphological characteristics, cytotoxicity, antimicrobial activity and stability of the developed system. The load efficiency of nisin in BC was evaluated by an agar diffusion assay, utilizing Lactobacillus sakei, and total proteins. After having found the ideal time and concentration for the loading process, the system stability was evaluated for 100 days at 4, 25 and 37 °C against Staphylococcus aureus and L. sakei. Thus, in this study, there is a system that proves to be efficient, once BC has enhanced the antimicrobial activity of nisin, acting as a selective barrier for other compounds present in the standard solution and protecting the peptide. After 4 h, with 45% of proteins, this activity was almost 2 log10 higher than that of the initial solution. Once the nisin solution was not pure, it is possible to suggest that the BC may have acted as a filter. This barrier enhanced the nisin activity and, as a consequence of the nisin loading, a stable N–BC system formed. The N–BC could create meaningful material for pharmaceutical and food applications.

Research of the Photostimulation Effect on the Lactobacillus Lactis Culture Productivity and Resulting Nisin Activity

The article concerns the study results of the photostimulation influence of the Lactobacillus lactis inoculum on the cultural effervescence and obtained nisin activity. The researchers used frozen Lactobacillus lactis inoculum to produce nisin. They activated the culture in a 5.0 ml sterile MRS tube kept in an incubator at 37 °C for 48 hours. Before incubation, Lactobacillus lactis culture was treated with blue spectrum light with a wavelength of 430–470 nm and a luminous flux intensity of 35 MW/cm2 for 1 hour (experimental group). Bacterial samples of the control group were not treated with light. A man used the MRS medium for fermentation. To determine the culture titer, the authors run sowing on the MRS medium. The researchers defined an oxidative stress influence on the Lactobacillus lactis stability by cultivation on an agar medium using 5 mmol of hydrogen peroxide. To identify the titer and resistance to oxidative stress before sowing, the cultures were treated with blue light with the specified characteristics and processing time. It enables to increase the nisin activity after 24 hours of bacterial cultivation compared to the control group by 19.3%, or by 558 IU/ml. The researchers proved that the titer of Lactobacillus lactis culture against the background of preliminary irradiation with blue spectrum light before cultivation is 56.3% higher than the samples of the control group. Treatment of Lactobacillus lactis culture with blue spectrum light increases its viability under oxidative stress by 75%.

Cyclodextrin-Based Nanosponges as Perse Antimicrobial Agents Increase the Activity of Natural Antimicrobial Peptide Nisin.

At present, antibiotic resistance is considered a real problem. Therefore, for decades scientists have been looking for novel strategies to treat bacterial infections. Nisin Z, an antimicrobial peptide (AMP), can be considered an option, but its usage is mainly limited by the poor stability and short duration of its antimicrobial activity. In this context, cyclodextrin (CD)-based nanosponges (NSs), synthesized using carbonyldiimidazole (CDI) and pyromellitic dianhydride (PMDA), were chosen for nisin Z loading. To determine the minimum inhibitory of nisin Z loaded on CD-NS formulations, agar well diffusion plates were used. Then, the bactericide concentrations of nisin Z loaded on CD-NS formulations were determined against Gram-positive (Staphylococcus aureus) and -negative (Escherichia coli) bacteria, using microdilution brain heart infusion (BHI) and tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The minimum and bactericide inhibitory values of the nisin complex with NSs were potentially decreased against both bacteria, compared with the nisin-free sample, while the nisin complex with β-CD showed lower antibacterial activity. The antimicrobial effect was also demonstrated by free NSs. Furthermore, the total viable counts (TVCs) antibacterial experiment indicated that the combination of nisin Z in both PMDA and CDI β-CD-based NSs, especially CDI, can provide a better conservative effect on cooked chicken meat. Generally, the present study outcomes suggest that the cross-linked β-CD-based NSs can present their own antimicrobial potency or serve as promising carriers to deliver and enhance the antibacterial action of nisin Z.

Effect of Bacteriocin (ALC102) of Enterococcus faecium GRD AA on Biofilm Forming Listeria monocytogenes MTCC 657

Antilisterial bacteriocin producing strain were isolated from milk samples and were subjected to 16S rRNA sequencing and found to be of genus Enterococcus faecium. The bacteriocin ALC102 were partially purified by Amberlite XAD-16 adsorption followed by column chromatography. The biofilm formation capacity of Listeria monocytogenes MTCC 657 were evaluated by tube method and CV binding assay. Biofilm formation on different abiotic substrates were also evaluated. Among three substrates stainless steel had a strong biofilm formation followed by glass and aluminum foil. From the results of biofilm eradication studies, the bacteriocin ALC102 showed almost similar activity of commercial bacteriocin nisin on all the substrates at 45°C, 30°C, 4°C and -20°C. Based on CBD® biofilm eradication assay, the eradication potential of ALC102 and nisin were found to be similar on high (45°C) and freezing (-20°C) temperatures. From the study, antilisterial bacteriocin ALC102 found to be able to inhibit the biofilm formed Listeria monocytogenes MTCC 657 at different temperatures and different incubation periods (24h, 48h and 72h). The biofilm eradication potential of antilisterial bacteriocin ALC102 was similar to nisin. Neither incubation temperature nor incubation period doesn’t altered the activity of the bacteriocin. So this bacteriocin can be considered as a potential competitor in food industry and we strongly recommend the use of this bacteriocin from Enterococcus faecium GRD AA in the food preservation industry to a higher temperature (45°C) to freezing temperature (-20°C).

Stabilization and Anticancer Enhancing Activity of the Peptide Nisin by Cyclodextrin-Based Nanosponges against Colon and Breast Cancer Cells.

The great variability of cancer types demands novel drugs with broad spectrum, this is the case of Nisin, a polycyclic antibacterial peptide that recently has been considered for prevention of cancer cells growth. As an accepted food additive, this drug would be very useful for intestinal cancers, but the peptide nature would make easier its degradation by digestion procedures. For that reason, the aim of present study to investigate the protective effect of two different β-cyclodextrin-based nanosponges (carbonyl diimidazole and pyromellitic dianhydride) and their anti-cancer enhancement effect of Nisin-Z encapsulated with against colon cancer cells (HT-29). To extend its possible use, a comparison with breast (MCF-7) cancer cell was carried out. The physicochemical properties, loading efficiency, and release kinetics of Nisin complex with nanosponges were studied. Then, tricin-SDS-PAGE electrophoresis was used to understand the effect of NSs on stability of Nisin-Z in the presence of gastric peptidase pepsin. In addition, the cytotoxicity and cell membrane damage of Nisin Z were evaluated by using the MTT and LDH assay, which was complemented via Annexin-V/ Propidium Iodide (PI) by using flowcytometry. CD-NS are able to complex Nisin-Z with an encapsulation efficiency around 90%. A protective effect of Nisin-Z complexed with CD-NSs was observed in presence of pepsin. An increase in the percentage of apoptotic cells was observed when the cancer cells were exposed to Nisin Z complexed with nanosponges. Interestingly, Nisin Z free and loaded on PMDA/CDI-NSs is more selectively toxic towards HT-29 cells than MCF-7 cancer cells. These results indicated that nanosponges might be good candidates to protect peptides and deliver drugs against intestinal cancers.

Gastrointestinal Stability and Cytotoxicity of Bacteriocins From Gram-Positive and Gram-Negative Bacteria: A Comparative in vitro Study.

Bacteriocins are receiving increased attention as potent candidates in food preservation and medicine. Although the inhibitory activity of bacteriocins has been studied widely, little is known about their gastrointestinal stability and toxicity toward normal human cell lines. The aim of this study was to evaluate the gastrointestinal stability and activity of microcin J25, pediocin PA-1, bactofencin A and nisin using in vitro models. In addition cytotoxicity and hemolytic activity of these bacteriocins were investigated on human epithelial colorectal adenocarcinoma cells (Caco-2) and rat erythrocytes, respectively. Pediocin PA-1, bactofencin A, and nisin were observed to lose their stability while passing through the gastrointestinal tract, while microcin J25 is only partially degraded. Besides, selected bacteriocins were not toxic to Caco-2 cells, and integrity of cell membrane was observed to remain unaffected in presence of these bacteriocins at concentrations up to 400 μg/mL. In hemolysis study, pediocin PA-1, bactofencin A, and nisin were observed to lyse rat erythrocytes at concentrations higher than 50 μg/mL, while microcin J25 showed no effect on these cells. According to data indicating gastrointestinal degradation and the absence of toxicity of pediocin PA-1, bactofencin A, and microcin J25 they could potentially be used in food or clinical applications.

Synergistic antimicrobial interactions of nisin A with biopolymers and solubilising agents for oral drug delivery

In order to develop bacteriocins, like the lantibiotic nisin A, into effective alternatives to existing antibiotics, their biophysical and physicochemical properties must first be assessed, from solubility, to susceptibility and absorption. It has been well established that formulation strategies at early drug development stages can be crucial for successful outcomes during preclinical and clinical phases of development, particularly for molecules with challenging physicochemical properties. This work elucidates the physicochemical challenges of nisin A in terms of its susceptibility to digestive enzymes like pepsin, pancreatin and proteinase K and its poor solubility at physiological pHs. Low solution concentrations, below the minimum inhibitory concentration against Staphylococcus aureus, were obtained in phosphate buffered saline (PBS, pH 7.4) and in fasted state simulated intestinal fluid (FaSSIF, pH 6.5), while higher solubilities at more acidic pH’s such as in a KCl/HCl buffer (pH 2) and in fasted state simulated gastric fluid (FaSSGF, pH 1.6) are observed. Tween® 80 (0.01% v/v) significantly increased the solution concentration of nisin A in PBS (pH 7.4, 24 hr). Pancreatin doubled nisin A’s solution concentration at pH 7.4 (PBS) but reduced its’ inhibitory activity to ∼ 20%, and pepsin almost completely degraded nisin (after 24 hr), but retained activity at biologically relevant exposure times (∼15 min). Harnessing synergism between nisin A and either glycol chitosan or ε-poly lysine, combined with the solubilizing effect of Tween®, increased the antimicrobial activity of nisin A six fold in an in vitro oral administration model.

Inhibitory activities of propolis, nisin, melittin and essential oil compounds on Paenibacillus alvei and Bacillus subtilis.

BackgroundNatural products represent important sources of antimicrobial compounds. Propolis and compounds from essential oils comprise good examples of such substances because of their inhibitory effects on bacterial spores, including bee pathogens.MethodsEthanol extracts of propolis (EEP) from Apis mellifera were prepared using different methods: double ultrasonication, double maceration and maceration associated with ultrasonication. Together with the antimicrobial peptides nisin and melittin, and compounds present in the essential oils of clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum), assays were carried out on one Bacillus subtilis isolate and Paenibacillus alvei (ATCC 6344) against vegetative and sporulated forms, using the resazurin microtiter assay. Synergism with all the antimicrobials in association with tetracycline was verified by the time-kill curve method. Potassium and phosphate efflux, release of proteins and nucleic acids were investigated.ResultsEEPs showed the same MIC, 156.25 µg/mL against B. subtilis and 78.12 µg/mL against P. alvei. The peptides showed better activities against B. subtilis (MIC of 12 µg/mL for melittin and 37.50 µg/mL for nisin). Antimicrobials showed similar inhibitory effects, but cinnamaldehyde (39.06 µg/mL) showed the best action against P. alvei. Melittin and nisin showed the greatest capacity to reduce spores, regarding B. subtilis there was a 100% reduction at 6.25 and 0.78 µg/mL, respectively. Concerning P. alvei, the reduction was 93 and 98% at concentrations of 80 µg/mL of melittin and 15 µg/mL of nisin. EEPs showed the highest effects on the protein release against B. subtilis and P. alvei. Nucleic acid release, phosphate and potassium efflux assays indicated bacterial cell membrane damage. Synergism between antimicrobials and tetracycline was demonstrated against both bacteria.ConclusionAll antimicrobials tested showed antibacterial activities against vegetative and sporulated forms of P. alvei and B. subtilis, especially nisin and melittin. Synergism with tetracycline and damage on bacterial cell membrane also occurred.

Fabrication of zein-modified starch nanoparticle complexes via microfluidic chip and encapsulation of nisin

A microfluidic chip is a micro-reactor that precisely manipulates and controls fluids. Zein is a group of prolamines extracted from corn that can form self-assembled nanoparticles in water or a low concentration of ethanol in a microfluidic chip. However, the zein nanoparticles have stability issues, especially in a neutral pH environment due to the proximity of the isoelectric point. This study was designed 1) to evaluate the effect of octenyl succinic anhydride (OSA) modified starch on the stability of zein nanoparticles formed using a microfluidic chip and 2) to apply the zein-OSA starch for encapsulation of nisin and evaluate its anti-microbial activity in a model food matrix. A T-junction configuration of the microfluidic chip was used to fabricate the zein nanoparticles using 1% or 2% zein solution and 0–10% (w/w) of OSA starch solution. The stability of the nanoparticles in various ionic strength environments was assessed. Encapsulation efficiency and anti-microbial activity of nisin in the zein nanoparticles against Listeria monocytogenes in a fresh cheese were measured. As the concentration of OSA starch increased from 0 to 10%, effective diameter increased from 117.8 ± 14.5 to 198.7 ± 13.9 nm without affecting polydispersity indexes and zeta-potential changed toward that of the modified starch indicating the zein surface coverage by the OSA starch. The zein-OSA starch nanoparticle complexes were more stable at various sodium chloride concentrations than the zein nanoparticles without OSA starch. The encapsulation efficiency of nisin was positively correlated with the OSA starch concentration. The anti-microbial activity of nisin in the fresh cheese also increased until 3-days of storage as the concentration of the OSA starch increased, which presented both a potential and challenge toward applications.

Green Synthesis of Silver Nanoparticles Using Nisin and its Antibacterial Activity against Pseudomonas aeruginosa.

Background:Green synthesized silver nanoparticles (AgNPs) have been used in a wide range of biological applications, including their use as antimicrobial agents. The aim of this study was to evaluate the antibacterial activity of green synthesis AgNPs using nisin against Pseudomonas aeruginosa (P. aeruginosa).Materials and Methods:In order to synthesize Ag-nisin, a 1 mg/ml nisin solution was mixed with a 1-mM silver nitrate solution and incubated. The Fourier transform infrared spectroscopy (FTIR) analysis was employed to determine the presence of various biomolecules around AgNPs. The AgNPs were morphologically observed and characterized using field emission scanning electron microscopy assessment, dynamic light scattering (DLS), and zeta potential analysis. The microdilution broth method based on CLSI principles was used for the assessment of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of nisin on P. aeruginosa isolates.Results:Field emission scanning electron microscope showed spherical shaped nanoparticles. DLS revealed that the average size of nanoparticles was 37.2 nm. The zeta potential of AgNPs was − 13.3 mV. FTIR findings revealed that nitrogen atoms of nisin’s amine and amide groups are responsible for the capping and stability of the nanoparticles. The MIC and MBC showed that Ag/nisin nanoparticles had higher antimicrobial activity than nisin or AgNPs alone.Conclusion:The findings of this study show that the antibacterial activity of nisin can be increased by assembling it into the AgNP interface using a green chemical synthesis method. As a result, the technique may be used to develop an antibacterial formulation to enhance the effectiveness of nisin.

Impact of nisin on Clostridioides difficile and microbiota composition in a faecal fermentation model of the human colon.

Nisin is a bacteriocin with a broad spectrum of activity against Gram-positive bacteria. The aims were to assess nisin activity against Clostridioides difficile in a complex microbial environment and determine the minimum inhibitory concentration at which C. difficile growth is suppressed whilst having minimal impact on the faecal microbiota. Faecal slurries were prepared from fresh faecal samples and spiked with C. difficile (106 CFU per ml). Nisin was added to each fermentation at a range of concentrations from 0 to 500µM. Following 24h, 16S rRNA gene sequencing was performed, and the presence of viable C. difficile was assessed. There was no viable C. difficile detected in the presence of 50-500µM nisin. There was a decrease in the diversity of the microbiota in a nisin dose-dependent manner. Nisin predominantly depleted the relative abundance of the Gram-positive bacteria whilst the relative abundance of Gram-negative bacteria such as Escherichia Shigella and Bacteroides increased. Using an ex vivo model of the colon, this study demonstrates the ability of purified nisin to selectively deplete C. difficile in a faecal microbial environment and establishes the minimum concentration at which this occurs whilst having a minimal impact on the composition of the microbiota. This study opens up the potential to use nisin as a therapeutic for clostridial gut infections.

Nisin Induces Cell-Cycle Arrest in Free-Living Amoebae Acanthamoeba castellanii.

Acanthamoeba spp. are free-living amoebas with worldwide distribution and play an important role as disease-causing agents in humans. Drug inability to completely eradicate these parasites along with their toxic effects suggest urgent need for new antimicrobials. Nisin is a natural antimicrobial peptide produced by Lactococcus lactis. Nisin is also the only bacteriocin approved for use in food preservation. In this work, we analyzed the effect of nisin on the growth of Acanthamoeba castellanii trophozoites. A total of 8 × 104 trophozoites were exposed to increasing concentrations of nisin to determine its activity. Changes in cell membrane and cellular cycle of trophozoites were investigated by flow cytometry, and nisin cytotoxicity in mammalian cells was evaluated in L929 cells by MTT method. After 24h exposure to increasing nisin concentrations, an IC50 of 4493.2IUmL-1 was obtained for A. castellanii trophozoites. However, after 72h a recovery in amoebic growth was observed, and it was no longer possible to determine IC50. Flow cytometry analysis showed that nisin has no effect on the membrane integrity. Treatment with nisin induced cell-cycle arrest during G1 and S phases in A. castellanii trophozoites, which recovered their growth after 72h. This is one of the first studies showing the effect of internationally approved nisin against A. castellanii trophozoites. Nisin caused cell-cycle arrest in trophozoites, momentarily interfering with the DNA replication process. The data highlight the amoebostatic activity of nisin, and suggest its use as an adjuvant for the treatment of infections caused by Acanthamoeba spp.