Nisin Solution Research Articles

Development of the product for pre-milking cow-udder care on the basis of nisin and lactic acid

Nisin is a natural antibacterial substance widely used in the food industry and other spheres. As nisin has no bactericidal effect on gram-negative bacteria, it is combined with organic acids. The work aimed at developing a product for pre-milking cow udder care based on nisin and lactic acid. The bactericidal effect of the solutions of nisin and lactic acid was determined using the method of radial diffusion in agar on test cultures S. aureus (ATCC 25923), E. coli (055К59 №3912/41), and Str. uberis (field strain). In the experiment was used nisin produced by Glory Chem Co., Ltd. (China), lactic acid food 80 % solution (“Klebrig”, Belgium). The content of lactic acid in 1.5 % solution was sufficient for detecting bactericidal action on cultures S. aureus і Str. uberis, and 2 % for E. coli. Nisin solution had a lower bactericidal effect on coccal forms of micro-organisms compared to lactic acid and was ineffective for gram-negative rods. S aureus cultures were sensitive to nisin in the case of 1,5 and 2 % content in the solution, and Str. uberis – in the case of 0.5 to 2 %. The study showed that the minimal substance content in the study variant of the agent was 1 % nisin and 1 % lactic acid, to which E. coli and S. aureus cultures are sensitive, and Str. uberis – highly sensitive. In the case of 1 % nisin and 1.5 % lactic acid content, all the studied micro-organisms are sensitive to such substances combination. In the case of the content of 1 % nisin and 2 % lactic acid, they are practically susceptible. Thus, when combined, nisin and lactic acid enhance each other's bactericidal effect and are more effective when used on test cultures of micro-organisms than they are separately. We have developed the studied agent variant for pre-milking cow udder care with the content of nisin – 1 %, lactic acid – 2 %, glycerine – 4 %, allantoin – 0.5 %, and water up to 100 %. The minimum inhibitory concentration of the agent in case of 30-second exposition on test cultures S. aureus and E. coli was in case of dissolution 1:1 and for Str. uberis – in case of dissolution 1:15.

Effect of Nisin-based pretreatment solution on dentin bond strength, antibacterial property, and MMP activity of the adhesive interface

ObjectiveTo evaluate the effect of a Nisin-based dentin pretreatment solution on microtensile bond strength, antibacterial activity, and matrix metalloproteinase (MMP) activity of the adhesive interface. Materials and methods100 human molars were sectioned to expose dentin. The teeth were assigned to five groups (n = 20), according to the dentin pretreatment: 0.5%, 1.0%, or 1.5% Nisin; 0.12% chlorhexidine (positive control), and no solution (negative control), and divided into 2 subgroups: no aging, and thermomechanical aging. Specimens were etched with 37% H3PO4 for 15 s and submitted to the dentin pretreatment. Then, they were bonded with an adhesive (Adper Single Bond 2) and a resin composite for microtensile bond strength (μTBS) evaluation. Antibacterial activity against Streptococcus mutans was qualitatively examined using an agar diffusion test. Anti-MMP activity within hybrid layers was examined using in-situ zymography. Data were analyzed with two-factor ANOVA and post-hoc Tukey’s test (α = 0.050). ResultsFor μTBS, significant differences were identified for the factors “solutions” (p = 0.002), “aging” (p = 0.017), and interaction of the two factors (p = 0.002). In the absence of aging, higher μTBS was observed for the group 0.5% Nisin. In the presence of aging, all groups showed similar μTBS values. All Nisin concentrations were effective in inhibiting the growth of S. mutans. Endogenous MMP activity was more significantly inhibited using 0.5% and 1.0% Nisin (p < 0.050). Conclusion0.5% and 1.0% Nisin solutions do not adversely affect resin-dentin bond strength and exhibit a potential bactericidal effect against S. mutans. Both concentrations effectively reduce endogenous gelatinolytic activity within the hybrid layer. Clinical relevanceThe use of 0.5% and 1.0% Nisin solutions for dentin pretreatment potentially contributes to preserving the adhesive interface, increasing the longevity of composite restorations.

One step purification of active nisin by electrodialysis from a commercial product

Nisin is a natural antimicrobial peptide widely used in food and medical applications. Its use is hampered by its costly production process and complex further purification. Therefore, electrodialysis process was used, for the first time, to purify a commercial nisin solution, in comparison with a conventional multiple-step centrifugation approach. Electrodialysis was, in one purification step, as efficient as the centrifugation process for nisin desalination (demineralization rate of 95.6% vs 94.3–99.8% respectively) with a higher protein recovery yield (83.8% vs 12.5–42.1% respectively). Centrifugation at higher concentration allowed the purification of nisin with the highest specific activity for supernatants S2 (3653.8–7307.6 AU/mg of proteins) and S3 (2394.2–9577.3 AU/mg of proteins). In a circular economy scheme, since saline effluents produced during centrifugation and precipitation processes represent an ecological and economical hurdle regarding their disposal, the use of electrodialysis would be of interest, by reusing the salts and lowering or eliminating the production of by-products.

Effect of probiotic drugs and their metabolites on the microflora of digestive canal of broiler chickens

The relevance of the study is conditioned by the growing demand of the population for safe and organic poultry products. Various microbiological preparations are used as therapeutic and preventive means and alternatives to the use of antibiotics in organic poultry farming. The purpose of the study is to determine the effect of preparations of probiotic microorganisms and their metabolites on the optimal composition of the microflora of the digestive canal, the general condition, and the liveability of broiler chickens. The effect of various types of drugs on broiler chickens was investigated: the probiotic LactoPharm LP12, the postbiotic Bacteriosan, and a bacteriocin nisin solution. The qualitative and quantitative composition of the microflora of the digestive canal of broiler chickens was determined by the method of bacteriological cultures. The disc diffusion method, using commercial discs with a minimum inhibitory concentration, revealed sensitivity to antibiotics. The effective effect of the new postbiotic Bacteriosan on the intestines of poultry was confirmed – no coagulase-positive Staphylococcus aureus was isolated on the 30th day of the experiment, and the lowest titre of Escherichia coli was recorded on days 30, 60, and 81 of the experiment. In terms of the content of lactic acid bacteria in the intestines of broiler chickens, the highest concentration was found in the experimental groups that used the probiotic LactoPharm LP12 and the experimental postbiotic by 21% and 32%, respectively, compared to control group. Treatment of bedding material with prophylactic drugs in poultry houses of experimental groups contributed to air sanitation and a decrease in the microbial background of the room compared to the control. The lowest mortality rate of chickens (-12%) was observed when using probiotics and postbiotics, due to the positive effect on the microbiocenosis of the digestive canal. When using an aqueous solution of nisin, the mortality rate was 14%. Thus, the use of the postbiotic Bacteriosan at a dose of 5 mL/kg of feed and the probiotic LactoPharm LP12 at a dose of 1 g/L of drinking water for seven days with a weekly break during the entire period of poultry rearing was experimentally substantiated, which will allow for effective prevention of infectious diseases and increase the liveability of broiler chickens

Bactericidal Effect of Combination of Atmospheric Pressure Plasma and Nisin on Meat Products Inoculated with Escherichia coli O157:H7.

This study was conducted to investigate the bactericidal effect of nisin (Nisin) only, atmospheric pressure plasma (APP) only, and a combination of APP and nisin (APP+Nisin) on beef jerky and sliced ham inoculated with Escherichia coli O157:H7, gram-negative bacteria. The bactericidal effect against E. coli O157:H7 and Listeria monocytogenes was confirmed using a nisin solution at a concentration of 0-100 ppm, and APP+Nisin was tested on beef jerky and sliced ham using 100 ppm nisin. Beef jerky and sliced ham were treated with APP for 5 min and 9 min, respectively. In the bacterial solution, 100 ppm nisin out of 0-100 ppm nisin exhibited the highest bactericidal activity against L. monocytogenes (gram-positive bacteria; p<0.05); however, it did not exhibit bactericidal effects against E. coli O157:H7 (gram-negative bacteria). The APP+Nisin exhibited a 100% reduction rate in both E. coli O157:H7 and L. monocytogenes compared to the control group, and was more effective than the Nisin. The APP+Nisin decreased the number of colonies formed by 0.80 and 1.96 Log CFU/g for beef jerky and sliced ham, respectively, compared to the control, and exhibited a higher bactericidal effect compared to the Nisin (p<0.05). These results demonstrate the synergistic bactericidal effect of APP and nisin, providing a possible method to improve the limitations of nisin against gram-negative bacteria. In addition, this technology has the potential to be applied to various meats and meat products to control surface microorganisms.

Harvest of nisin from fermentation broth using foam separation with the assistance of ultrasonic treatment: Foam property evaluation and antimicrobial activity retention

Nisin is a gene-encoded short peptide secreted by Lactococcus lactis subsp. lactis and it has wide applications in diverse fields. Foam separation was used for harvesting nisin from fermentation broth in the current work. First, the effects of pH, nisin concentration and gas type on foam property, surface tension and antimicrobial activity of unitary nisin solution were investigated, respectively. At the suitable pH of 5.0, the critical micelle concentration (cmc) of nisin was 2.891 g/L. As nisin concentration exceeded cmc, the foam stability of sample solution gradually decreased. Among four gases, nitrogen (N2) gas could be selected as the suitable carrier gas for foam formation. Moreover, foam evolution could induce the modification of the nisin secondary structure, resulting in the loss of antimicrobial activity. In batch fermentation, the variations in biomass, nisin concentration and pH over cultivation period were monitored. Experimental results indicated that batch fermentation could be terminated after cultivation for 21 h. The foam property of peptone and yeast extract at different pH conditions was analyzed. The high selectivity of foam separation for harvesting nisin achieved at pH 5.0. Response surface methodology was employed to optimize the operational conditions of foam separation. Finally, the inactivation percentage of nisin in the foamate could be effectively reduced by assembling 300 W ultrasonic treatment into foam separation. The novelty of current work prompts a search for understanding of how operational factors of foam separation affect biochemical property and structural stability of nisin, thereby facilitating the industrial manufacture of nisin.

Evidence of Self-Association and Conformational Change in Nisin Antimicrobial Polypeptide Solutions: A Combined Raman and Ultrasonic Relaxation Spectroscopic and Theoretical Study

The polypeptide Nisin is characterized by antibacterial properties, making it a compound with many applications, mainly in the food industry. As a result, a deeper understanding of its behaviour, especially after its dissolution in water, is of the utmost importance. This could be possible through the study of aqueous solutions of Nisin by combining vibrational and acoustic spectroscopic techniques. The velocity and attenuation of ultrasonic waves propagating in aqueous solutions of the polypeptide Nisin were measured as a function of concentration and temperature. The computational investigation of the molecular docking between Nisin monomeric units revealed the formation of dimeric units. The main chemical changes occurring in Nisin structure in the aqueous environment were tracked using Raman spectroscopy, and special spectral markers were used to establish the underlying structural mechanism. Spectral changes evidenced the presence of the dimerization reaction between Nisin monomeric species. The UV/Vis absorption spectra were dominated by the presence of π → π* transitions in the peptide bonds attributed to secondary structural elements such as α-helix, β-sheets and random coils. The analysis of the acoustic spectra revealed that the processes primarily responsible for the observed chemical relaxations are probably the conformational change between possible conformers of Nisin and its self-aggregation mechanism, namely, the dimerization reaction. The activation enthalpy and the enthalpy difference between the two isomeric forms were estimated to be equal to ΔH1* = 0.354 ± 0.028 kcal/mol and ΔH10 = 3.008 ± 0.367 kcal/mol, respectively. The corresponding thermodynamic parameters of the self-aggregation mechanism were found to be ΔH2* = 0.261 ± 0.004 kcal/mol and ΔH20 = 3.340 ± 0.364 kcal/mol. The effect of frequency on the excess sound absorption of Nisin solutions enabled us to estimate the rate constants of the self-aggregation mechanism and evaluate the isentropic and isothermal volume changes associated with the relaxation processes occurring in this system. The results are discussed in relation to theoretical and experimental findings.

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.

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.

Evaluation the Antibacterial Activity of the Brine, Nisin Solution, and Ozonated Water Against E. coli O157:H7 in the Experimentally Local Produced Soft Cheese

This study aimed to evaluate the antibacterial efficacy of brine solution in compared to nisin and ozonated water treatments against E. coli O157:H7 in experimentally local produced soft cheese (ELPSC). A total of 25 raw cow milk samples were collected from farmers and local markets in Baghdad city and utilized to manufacturing 25 of ELPSC samples following the traditional procedure in rural Iraq without salting or heat treatment. Bacteriological analysis for potential E. coli O157:H7 contamination was performed and confirmed by cultural, biochemical, and serological tests. Antibacterial activity of brine solution (7% w/v), nisin solution (100 IU/mL), and ozonated water (0.6 ppm) was performed for positive samples after 2 h contact time at ambient temperature. Positive isolates of E. coli O157:H7 were detected and confirmed as 3 out of 25 cheese samples (12%), with initial average bacterial count of 6.146 log10 CFU/g. The initial bacterial count was significantly (P&lt;0.05) reduced to 3.778, 4.380 and 4.544 log10 CFU/g when subjected to brine salting, nisin solution, and ozonated water, respectively. Cheese samples exposed to brine had a significantly (P&lt;0.05) higher reduction in the bacterial growth than those exposed to nisin or ozonated water treatments for each alone. More effective reduction in E. coli O157:H7 bacterial growth was not observed when brining exposure time elongated at ambient temperature to 6 h. These findings may be useful in raising the public knowledge about the use of brine solution as a domestic antibacterial approach for minimizing the possible risk of E. coli O157:H7 contamination in the local produced soft cheese.

Effective adsorption of nisin on the surface of polystyrene using hydrophobin HGFI

Herein, a new method was demonstrated for effective immobilization of the antibacterial peptide nisin on Grifola frondosa hydrophobin (HGFI), without the need of any additional complex reaction. Hydrophobin can self-assemble as a monolayer to form continuous negative-charged surfaces with enhanced wettability and biocompatibility. Adding nisin solution to such hydrophobin surface created antibacterial surfaces. The quantification analysis revealed that more nisin could be adsorbed on the HGFI-coated than to control polystyrene surfaces at different pH values. This suggested that electronic attraction and wettability may play important roles in this process. The transmission electron microscopy, atomic force microscopy and fourier transform infrared (FTIR) analysis indicated the adsorption mode of nisin on the HGFI film, i.e., hydrophobins served as an adhesive layer for binding charged peptides to interfaces. The antibacterial activity of the treated surface was investigated via counting, a nucleic acid release test, scanning electron microscopy, and biofilm detection. These results indicated the excellent antibacterial activity of nisin adsorbed on the HGFI-coated surfaces. The activity retention of adsorbed nisin was demonstrated by immersing the modified substrates in a flowed liquid condition.

In vitro and In vivo Antibacterial Effects of Nisin Against Streptococcus suis

Nisin is a promising therapeutic candidate because of its potent activity against Gram-positive bacteria. The present study aimed to describe the in vitro and in vivo antibacterial effects of nisin against Streptococcus suis, an important zoonotic pathogen. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of nisin against different S. suis strains ranged from 0.12 to 4.0μg/mL and from 0.25 to 8.0μg/mL, respectively. Time-killing curve assays illustrated that nisin killed 100% of tested virulent S. suis strains within 4h when used at 2× MIC, which indicates the rapid bactericidal activity of nisin against the bacteria. Transmission and scanning electron microscopy revealed that nisin destroyed S. suis cell membrane integrity and affected its cellular ultrastructure, including a significantly wrinkled surface, intracellular content leakage, and cell lysis. In addition, nisin inhibited biofilm formation by S. suis in a concentration-dependent manner and exhibited strong degrading activities against preformed biofilms. More importantly, nisin displayed antimicrobial activity against S. suis infection in vivo. Upon treatment with 5.0-10mg/kg nisin solution, the survival rates of mice challenged with a lethal dose of virulent S. suis virulent ranged 87.5-100%. Nisin significantly decreased bacterial proliferation and translocation in the mouse spleen, brain, and blood. These results indicate that nisin has potential as a novel antimicrobial agent for the clinical treatment and prevention of infection caused by S. suis in animals.

Effects of Nisin Treatment on the Shelf Life of Ready-to-Eat Roasted Shrimp (&amp;lt;i&amp;gt;Penaeus vannamei&amp;lt;/i&amp;gt;)

The microbiological, biochemical, and physicochemical changes of ready-to-eat shrimps (Penaeus vannamei) with high water content, subjected to nisin treatment in combination of hurdle technology, were investigated. The ready-to-eat shrimps were processed by boiling, drying, treatment with nisin solution, seasoning, and roasting, followed by vacuum packaging, sterilization, and storage at room temperature (25°C). The results showed that the samples treated with nisin in combination with other hurdles resulted in a significant decrease in bacterial counts (Bacillus cereus and native microflora) compared to the control samples. Additionally, the nisin-treated samples possessed better biochemical and physicochemical properties, as well as better sensory patterns. According to the safety guidelines for roasted shrimp (SC/T 3305-2003), the shelf life of ready-to-eat shrimp with 48–53% moisture content was extended by nisin application at concentrations of 60 and 100 mg/kg of nisin; specifically, ready-to-eat shrimp maintained good quality from 4–6 days up to 6–12 and 8–14 days corresponding to 60 and 100 mg/kg of nisin treatments, respectively. Nisin treatment combined with hurdle technology in the production of ready-to-eat shrimp provides a highly valued product in China.

DIPPING SOLUTIONS OF NISIN AND BUFFERED SODIUM CITRATE SUPPLEMENTED WITH SODIUM DIACETATE FAIL TO PREVENT GROWTH OF LISTERIA MONOCYTOGENES ON VACUUM PACKAGED BEEF FRANKFURTERS STORED AT 4 AND 10°C UNDER MODEL CONDITIONS

This study evaluated commercially available dip solutions of nisin alone, buffered sodium citrate combined with sodium diacetate (BSCSD), and combined solution of the three antimicrobials for potential to control growth of surface-inoculated Listeria monocytogenes during vacuum packaged refrigerated storage of model beef frankfurters. None of the treatments prevented growth of L. monocytogenes during Frankfurter storage. The combined treatments slowed growth of L. monocytogenes better than individual treatments. Failure to completely eliminate L. monocytogenes on frankfurters or inhibit outgrowth during storage might be attributed to high initial L. monocytogenes inoculum levels, insufficient quantities of antimicrobials to interact with all the target cells, low nisin activity at high pH, or presence of resistant subpopulations, such as nisin-resistant strains. The model conditions used in the experimental setup, such as elimination of natural microbiota from frankfurters and nutrient-rich diluent used for Listeria introduction on the surface, could also contributed to enhanced survival and growth of the pathogen.

Chemical and biological protection of food grade nisin through their partial intercalation in laminar hydroxide salts

The use of antimicrobial agents within a matrix, specifically layered compounds, is of growing interest for reducing contamination due to food borne pathogens and deteriorative microorganisms, one of the main health problems worldwide. In this study, zinc layered hydroxide nanoparticles were synthesized as a matrix for nisin immobilization. Layered materials were characterized by X-ray diffraction, Fourier-Transform Infrared and Ultra Violet-Visible spectra, Scanning Electron Microscopy, and by Thermogravimetric Analysis. Thermal, chemical, enzymatic, and biological stabilities were assessed against Lactobacillus brevis as control strain. Free and immobilized nisin in solution were previously subjected to 25 and 121°C, pH (7, 9) and inactivation with protease before antimicrobial tests that lasted 21days. Immobilized nisin was found to maintain the activity levels after the protease action while the pure nisin solution lost its activity gradually. Furthermore, immobilized nisin treated at 121°C and pH 7 showed higher activity than pure nisin after 21days. These results may support that immobilizing nisin in zinc layered hydroxide salts promoted extended nisin inhibitory activity in solution after thermal, chemical or enzymatic treatments. This research provides an alternative to nisin application that could be used in processes where such operating conditions take place, as in dairy products.

Farklı Konsantrasyonlarda Kullanılan Nisinin Soğukta ve Vakum Paketlenerek Depolanan Levrek (Dicentrarchus labrax, Linnaeus, 1758) Filetolarının Renk Değişimleri Üzerine Etkileri

Bu çalışmada farklı konsantrasyonlarda (%0,2, %0,4 ve %0,8) hazırlanan nisin solüsyonlarının levrek filetolarının soğukta ve vakum paketlenerek depolanması esnasında renk değişimleri üzerindeki etkileri incelenmiştir. Panelistler tarafından gerçekleştirilen duyusal analizlerde (çiğ ve pişmiş olarak) levreğin raf ömrü I. denemede kontrol grubunda 6 gün, nisin uygulanan gruplarda ise 8 gün olarak; II. denemede ise kontrol grubunda 12 gün, nisin uygulanan gruplarda ise 14 gün olarak belirlenmiştir. Nisin uygulanmasının balık etinin doğal kokusu ve aroması üzerine olumsuz bir etkisi gözlenmemiştir. Panelistler tarafından kontrol grubuna göre daha çok tercih edilmiş olan nisin uygulamasının levreğin raf ömrünü 2 gün uzattığı tespit edilmiştir. Elde edilen sonuçlar, filetolanmış levreğin tek başına nisin ile muamelesinde (Deneme I) ve vakum paketleme ile nisinin kombine kullanımları (Deneme II) sonucunda rengini daha iyi koruduğunu, 4±2°C‘de deneme I‘ de 12 günlük ve deneme II‘de 18 günlük depolamada daha iyi renk sonuçları ile kontrol grubundan daha iyi tüketici algısı oluşturmuştur. Sonuç olarak nisin uygulaması, filetoların renk stabilitesi üzerine pozitif etki yapmıştır. Mevcut çalışma sonucunda elde edilen bulgular, su ürünlerinin kalitesi ve kontrolü üzerine yararlı bilgiler içermektedir. İnsan sağlığı üzerinde olumlu etkilere sahip alternatif doğal bir koruyucu olarak nisinin kullanımı hakkında gıda sektörü ve tüketicilerin bilgilendirilmesinin ekonomik ve sosyal bir yaygın etki sağlayabileceği öngörülmektedir.

Bacterial nanocellulose membranes combined with nisin: a strategy to prevent microbial growth

Consumer concerns about synthetic additives is increasing and it can be interesting to apply natural antioxidants with antimicrobial properties. Developing a packing material composed by a natural polymer, such as bacterial nanocellulose membrane (BNCm) loaded with nisin may be applied as a method to keep food quality and to inhibit growth of microbial contaminants. For this reason, the aim of this study was to evaluate antimicrobial activity of BNCm loaded with nisin. Antimicrobial activity of nisin, utilizing or not EDTA solution,was assessed by minimal inhibitory concentration and agar diffusion assay, utilizing Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Antioxidant activity and physico-chemical properties were also evaluated. For the MIC evaluation, the combination of nisin solution with EDTA showed a synergistic effect. Concerning E. coli nisin with EDTA 20–40 mM, MIC was 31.25 μg/mL. Concerning P. aeruginosa nisin with EDTA 10–20 mM, MIC was 125 μg/mL. Concerning S. aureus nisin with EDTA 10 mM, MIC was 15.63 μg/mL, two times lower than without EDTA. The BNCm antimicrobial activity for E. coli, by agar diffusion assay, was observed when nisin was loaded at 250 or 500 μg/mL with EDTA 10 or 20 mM. However, for S. aureus, the antimicrobial activity was observed for BNCm loaded with nisin 15 μg/mL with 10 mM EDTA. For P. aeruginosa, antimicrobial activity was not observed. Nisin exhibited significant antimicrobial and antioxidant activity. The results provide evidence that BNCm loaded with nisin is a promising control strategy to prevent microorganism contamination.

Effect of high pressure on the antimicrobial activity and secondary structure of the bacteriocin nisin

Abstract Effect of high pressure (HP) treatment on the antimicrobial properties and the structure of nisin was evaluated. Nisin solutions at pH 2.8 or 6.1 were treated by HP at 500 MPa – 10 min – 20 °C and their antimicrobial potency was determined. It appeared that HP clearly impacted the antimicrobial activity of nisin, with respective activity loss of 22.5% and 49.9% at pH 2.8 and 6.1. Structural analysis of nisin by circular dichroism and Fourier transform-infrared spectroscopies revealed that the decrease of nisin antimicrobial activity was likely due to the unfolding of the protein induced by HP. A loss of nisin β-turns structure, particularly significant at neutral pH, was linked to the drastic drop in antimicrobial activity, as these structures are implicated in the nisin interaction with the bacterial membrane. Industrial relevance The combination of nisin and high pressure (HP) can be use at an industrial scale to inactivate bacteria. Nisin is allowed as a food additive (E234) and can be added at a final concentration ranging from 120 to 500 IU/g, depending on the product. In this work, we showed that HP can induce a significant reduction of nisin activity (-22.5% at pH 2.8 and -49.9% at pH 6.1). Therefore, this activity loss could be taken into account to manage the final nisin concentration in HP-treated food products.

Determining the effects of green chemistry synthesized Ag-nisin nanoparticle on macrophage cells

Bacteriocins are low molecular weight substances produced through post transcriptional changes. These molecules are easily degraded in mammalian gut by proteolytic enzymes especially protease. Nisin is a peptide with 34 aa and its structure contains a pentacyclic lanthionine and 4 beta metyllanthionine residues. Different formulations have been designed for nisin. Since “green synthesis” is a progressive method to prepare anti-microbial and anti-cancer compounds, this study aimed at green synthesis of nisin metal compounds to be used lower concentration still exerting nisin effects. For this purpose, a 1 mg/ml nisin solution was added to a 1 mM silver nitrate solution and incubated to synthesis nano Ag-nisin, then the optical density of new solution was detected using UV spectroscopy. To determine biomolecules in the Ag-nisin solution, the FTIR method was employed. The size and morphology of Ag-nisin was measured by TEM. The toxicity, inflammatory cytokines production, and intracellular ROS quantity was evaluated using MTT, ELISA and flow-cytometry. XRD pattern indicated the silver crystals in Ag-nisin solution. In addition, FTRI findings showed that the carbonyl groups of amino acid are potently able to bind to metal nanoparticles, cover, and prevent them from particle agglomeration. Treating macrophage cells with 10, 25, 50 and 100 μg/ml of Ag-nisin had no significant effect on the cell viability and intracellular ROS quantity compared to the control group. In addition, different concentrations of Ag-nisin had no effect on the IL-10 and TNF-α levels but caused an increased level of IL-12 in comparison with the control group.In the current study, for the first time, green synthesize was used to prepare Ag-nisin particles. The synthesized nanoparticle is able to induce inflammatory activity via increasing IL-12 without any change in the TNF-α level in macrophage cells.

Preparation and optimization of self-assembled chondroitin sulfate-nisin nanogel based on quality by design concept

Self-assembled nanogel was prepared by electrostatic complexation of two oppositely charged biological macromolecules, which were cationic nisin and anionic chondroitin sulfate (ChS). The critical factors affected the physical properties of ChS-nisin nanogel was screened and optimized by Plackett-Burman design (PB) and central composite design (CCD). The independent factors selected were: concentration ratio of nisin to ChS, injection rate of nisin solution, buffer solvent type, magnetic stirring rate, pH of initial buffer solution, centrifuge-cooling temperature, and centrifuge rotation speed. Among these factors, concentration ratio changed the entrapment efficiency and loading capacity significantly. In addition, the hydrodynamic diameter and loading capacity were significantly influenced by injection rate and pH of initial buffer solution. The optimized nanogel structure was obtained by concentration ratio of 6.4mg/mL nisin to 1mg/mL ChS, pH of buffer solution at 4.6, and nisin solution injection rate of 0.2mL/min. The observed values of dependent responses were close to predicted values confirmed by model from response surface methodology. The results obviously showed that quality by design concept (QbD) could be effectively applied to optimize the developed ChS-nisin nanogel.