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  Nowadays foods are preserved with using some methods to minimize contamination. One of these methods is food preservatives. Food preservatives with antagonistic effect usually interfere with cell membrane, enzyme action or genetic structure of microorganisms. In this investigation the effects of some preservatives were studied on the growth curve of Listeria monocytogenes that is isolated from dairy products. First the growth curve of bacteria was drawn when the preservatives were absent. Then the growth curve of bacteria was drawn when citric acid, which is a chemical preservative and nisin, which is a natural preservative, were present at sub-MIC concentrations. Next the growth curve of bacteria was drawn at the presence of both acetic acid and sodium citrate at different concentrations and in this period the changes of pH were measured. Listeria monocytogenes did not grow against citric acid at any sub-MIC concentrations which shows the sensitivity of bacteria to citric acid. Although this bacterium was sensitive to MIC concentrations of nisin, but it was significantly resistant to nisin after 18 hours. Also acetic acid and sodium citrate together can have more effect against this bacterium. This study showed that food isolated Listeria monocytogenes is resistant to sub-MIC concentrations of some preservatives, so it is suggested not to apply less concentration of MIC concentrations.

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Aim: Group A Streptococcus (GAS) is the causative agent of several invasive and non-invasive diseases. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes. Due to the improper use of antibiotics, the resistance of these microorganisms to antibiotics is increasing. Bacteriocins as an alternative to antibiotics are of great importance. In this study, the effect of antimicrobial Bacteriocin nisin was investigated on the expression of smeZ gene.
Materials & Methods: Samples were taken from the site of infection on the skin surface of the patients at the dermatology clinics of Tehran public hospitals. The specimen was immediately transferred to the primary culture medium or basal medium. Chromosomal DNA extraction was performed using the standard method for the extraction of Streptococcus pyogenes genomes. Multiplex PCR was performed to identify the presence of smeZ, speI, and speH genes in the isolates. The expression of smeZ gene was evaluated using the real-time PCR technique.
Findings: The frequencies of smeZ, speI, and speH genes in 12 S. pyogenes isolates were 25, 8.3, and 8.3%, respectively. The fold change rate for smeZ gene was -1.209, indicating that this gene was decreased 1.209 folds in the treated group compared to the untreated group.
Conclusion: Bacteriocin not only reduces the number of pathogens but may also affect the metabolism of the bacteria by producing toxins. The use of new antimicrobial agents in place of previous drugs for psoriasis patients could be considered as a way to treat the disease more effectively in the future.
 

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Supplying fresh fish and sea products is accompanied with the problem of their rapid spoilage and short shelf life. Therefore, solutions which help increase this shelf life have always been valued. Accordingly, the aim of this study was to evaluate the effect of whey protein coatings containing four different concentrations (100,200,400 and 800 IU/gr) of nisin in perch fillet for storage in refrigerator temperature. Humidity tests, Peroxide Value, Thiobarbituric acid Index, microbial load, water activity and pH were performed over coated and uncoated samples. The results indicated that increasing the shelf life in all treatments led to an increase in peroxide value, Thiobarbituric acid Index, the load of bacteria, pH and water activity, this increase was less in coated samples than the uncoated ones. On the other hand, the findings showed that whey protein and nisin coating with the of concentration 400 IU/gr of perch fillet can add 16 days to increase the shelf life in refrigerator temperature in comparison with the uncoated samples. Based on our findings, it can be concluded that using whey protein coating containing nisin with the concentration of 400 IU/gr of perch fillet as edible coating  can increase the shelf life in the refrigerator temperature.

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Background: A promising strategy in cancer therapy involves the production of fusion proteins, which entail the fusion of two distinct proteins. This study aimed to produce and assess the cytotoxic effects of the Nisin-arginine deiminase (ADI) fusion protein on the SW480 cell lines, a common model for studying colorectal cancer (CRC).
Materials & Methods: The designed Nisin-ADI gene fragment sequence was sent to Biomatik Company for synthesis in pET-28a vectors between SacI and HindIII restriction enzyme sites. Escherichia coli (E. coli) DH5α and BL21 were utilized for cloning and protein expression, respectively. The recombinant fusion protein expression was induced by Isopropyl ß-D-1-thiogalactopyranoside (IPTG) and purified using Ni2+-nitrilotriacetic acid (1) resin affinity chromatography. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting were conducted to analyze the purified protein. The cytotoxic effect of the purified recombinant fusion protein on SW480 and NIH3T3 cells, as a control, was evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay.
Findings: The results of this study showed that the fusion protein had a significant impact on the SW480 cell lines. The Half-maximal inhibitory concentration (IC50) of the fusion protein was 30 µg/mL, indicating that it effectively inhibited the growth of cancer cells. However, the fusion protein did not significantly affect the control group.
Conclusion: This study provides helpful insights into the potential application of recombinant Nisin-ADI fusion proteins as a potential treatment option for colorectal cancer. The potential for selective targeting of cancer cells is promising as normal cells are unaffected by this fusion protein.

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The aquatic zoonotic bacterial Streptococcus iniae represents a threat to the worldwide aquaculture industry. This study was carried out to evaluate the antibacterial activity Cuminum cyminum essential oil and nisin for control of S.iniae in fillets of Rainbow trout (Oncorhynchus mykiss) in 4 Cº on basis hurdle technology between 2012 and 2013.The effect of different concentrations of nisin (0, 0.25 and 0.75 µg/ml) and Cuminum cyminum (0, 0.005, 0.135 and 0.405 %) were conducted on growth of S.iniae GQ850377 for 15 days. The results showed that growth of bacterial delayed in samples treated with nisin and essential oil singly to 9 days and together to 3 days. Samples treated with essential oil showed a significant decrease on the growth of the bacteria compared with nisin and control sample (P<0.05). No significant different was observed on the growth of S.iniae in samples treated with higher concentrations of C.cyminum (0.135 and 0.405 %) (p>0.05), but different concentrations of nisin was statistically significant (p<0.05). Synergistic effects were observed at concentration of 0.405% C.cyminum and 0.75 µg/mL nisin.  

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Objective: Fusarium species are prevalent contaminants of foodstuffs and agricultural crops.  They produce fumonisins, which are carcinogenic mycotoxins. The present study has evaluated maize and wheat samples from ten provinces in Iran that were contaminated with Fusarium species. Special attention was paid to the ability of the isolates to produce fumonisin B₁ (FB₁) as a public health hazard. Methods: We collected 32 maize and 15 wheat samples from ten provinces that were major cultivation areas. Samples surface disinfected with a 1% sodium hypochlorite solution for 2 minutes. Fusarium species were isolated by the flotation method on malachite green agar. Pure cultures on potato dextrose agar (PDA) were identified using a combination of macroscopic and microscopic morphological criteria. The ability of the isolates to produce FB₁ was evaluated by thin layer chromatography (TLC) and the amounts of fumonisin B₁ produced were assessed by high performance liquid chromatography (HPLC). Results: A total of 55 Fusarium isolates that belonged to five species were isolated. There were 27 of the 32 maize samples (84.4%) and 11 of 15 wheat samples (73.3%) that were contaminated with Fusarium species. Species consisted of F. verticillioides (23 isolates), F. proliferatum (22 isolates), F. subglutinans (5 isolates), F. nygamai (4 isolates) and F. redolens (1 isolate) based on morphological criteria. Twenty-two of the 55 (40%) Fusarium isolates produced FB₁ in a total range from 230.4 to 9565 µg/ml. The highest amounts of FB₁ production were related to toxigenic isolates of F. verticillioides and F. proliferatum. Conclusion: Results of the present work indicates a high degree of contamination of maize and wheat with Fusarium strains that belong to the Gibberella fujikuroi species complex وparticularly F. verticillioides and F. proliferatum. This contamination is a potential public health threat due to food spoilage and subsequent production of high levels of carcinogenic FB₁.

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The aim of this study was to investigate the properties of polyethylene antimicrobial film containing niacin and limonene microcapsules in cheese process packaging. In this study microcapsules containing nisin (0.5, 1, 1.5, 2 and 2.5) and limonene (5, 7, 10, 14, 21 and 28 µg / mg) were prepared by gelation method. . After optimization, niacin and limonene microcapsules were used in polyethylene film based film formulation. After packaging cheese cheese in the film containing optimized microcapsules containing concentrations (1, 1.5 and 2 µg / mg nisin and 5, 7 and 10 µg / mg limonene), total microbial populations, mold and Yeast, Staphylococcus coagulase positive, Escherichia coli were examined on the first days of production, 20th, 40th, and 60th storage.
The results were analyzed by two-way ANOVA and Duncan tests at the significant level of 0.05. During 60 days of storage, total microbial indices, mildew and yeast, Staphylococcus coagulas positive and Escherichia coli significantly decreased (p≤0.05).
 The results showed that treatment with Nisin containing 2 IU / mg concentration and limonene with concentration of 10 µg / mg resulted in higher quality of processed cheese during storage period and were selected as optimal treatment.