Antimicrobial Activity Of Bacteriocin Research Articles

Study of the Effect of Bacteriocin-producing Bacillus subtilis Strains on Beta-lactamase-producing Pathogenic Bacteria

Background: The emergence of antimicrobial resistance results in morbidities and mortalities associated with many bacterial infections and is a major concerning issue in front of the healthcare system. As a part of a competitive adaptive strategy for its growth, gram-positive bacteria like Bacillus subtilis produce antimicrobial peptides; bacteriocins. These peptides protect other bacterial species. Objectives: To counter antimicrobial resistance, bacteriocins can be considered a potential drug option against drug-resistant microorganisms. Methods: After isolation and characterisation of B. subtilis from the 5 collected soil samples, the bacteriocin was extracted from these bacteria by using the ‘solvent extraction method’, characterised, and then purified to evaluate its antimicrobial activity against pathogenic bacteria like; Streptococcus pyogenes, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii by using ‘Kirby-Bauer disc diffusion’, method. The bacteriocin stability was also investigated, at different temperatures, pH and incubation times. Results: The bacteriocin of B. subtilis showed great antimicrobial activity against S. pyogenes, followed by S. typhi and P. aeruginosa. However, the lowest antimicrobial activity was against A. baumannii. With the increase in the incubation time and temperature, the antimicrobial activity of bacteriocin was decreased, indicating the protein nature of bacteriocin. Compared to the standard antibiotics, the bacteriocin isolated from B. subtilis demonstrated a significant inhibitory effect against the tested pathogens. Conclusions: From this study, it can be concluded that bacteriocin can become a potential alternative to standard available medicines. They can be used against antimicrobial-resistant pathogenic bacteria because of their significant inhibitory activity against the tested pathogens compared to the standard antibiotics.

Scientists' Assessments of Research on Lactic Acid Bacterial Bacteriocins 1990-2010.

The antimicrobial activity of bacteriocins from lactic acid bacteria has constituted a very active research field within the last 35 years. Here, we report the results of a questionnaire survey with assessments of progress within this field during the two decades of the 1990s and the 2000s by 48 scientists active at that time. The scientists had research positions at the time ranging from the levels of Master’s and Ph.D. students to principal investigators in 19 Asian, European, Oceanian and North American countries. This time period was evaluated by the respondents to have resulted in valuable progress regarding the basic science of bacteriocins, whereas this was not achieved to the same degree with regard to their applications. For the most important area of application, food biopreservation, there were some success stories, but overall the objectives had not been entirely met due to a number of issues, such as limited target spectrum, target resistance, poor yield as well as economic and regulatory challenges. Other applications of bacteriocins such as enhancers of the effects of probiotics or serving as antimicrobials in human clinical or veterinary microbiology, were not evaluated as having been implemented successfully to any large extent at the time. However, developments in genomic and chemical methodologies illustrate, together with an interest in combining bacteriocins with other antimicrobials, the current progress of the field regarding potential applications in human clinical microbiology and food biopreservation. In conclusion, this study illuminates parameters of importance not only for R&D of bacteriocins, but also for the broader field of antimicrobial research.

Genomic and functional characterization of bacteriocinogenic lactic acid bacteria isolated from Boza, a traditional cereal-based beverage

Boza is a traditional low-alcohol fermented beverage from the Balkan Peninsula, frequently explored as a functional food product. The product is rich in Lactic Acid Bacteria (LAB) and some of them can produce bacteriocins. In this study, a sample of Boza from Belogratchik, Bulgaria, was analyzed for the presence of bacteriocinogenic LAB, and after analyses by RAPD-PCR, three representative isolates were characterized by genomic analyses, using whole genome sequencing. Isolates identified as Pediococcus pentosaceus ST75BZ and Pediococcus pentosaceus ST87BZ contained operons encoding for bacteriocins pediocin PA-1 and penocin A, while isolate identified as Pediococcus acidilactici ST31BZ contained only the operon for pediocin PA-1 and a CRISPR/Cas system for protection against bacteriophage infection. The antimicrobial activity of bacteriocins produced by the three isolates was inhibited by treatment of the cell-free supernatants with proteolytic enzymes. The produced bacteriocins inhibited the growth of Listeria monocytogenes, Enterococcus spp. and some Lactobacillus spp., among other tested species. The levels of bacteriocin production varied from 3200 to 12,800 AU/ml recorded against L. monocytogenes 104, 637 and 711, measured at 24 h of incubation at 37 °C. All bacteriocins remained active after incubation at pH 2.0–10.0. The activity mode of the studied bacteriocins was bactericidal, as determined against L. monocytogenes 104, 637 and 711. In addition, bactericidal activity was demonstrated using a cell leakage β-galactosidase assay, indicating a pore formation mechanism as a mode of action. The present study highlights the importance of combining genomic analyses and traditional microbiological approaches as way of characterizing microbial interactions in fermented foods.

In-vitro Characterization and Purification of Bacteriocins Isolated from Probiotic Curd Culture

Introduction: Bacteriocins, the polypeptides secreted from probiotics proves to be a better choice of antimicrobials than that of synthetic antibiotics due to their negligible side effects and low cost. The present research focusses on the isolation of bacteriocin producing probiotic strains from homemade curd having good antagonistic properties against acne causing bacteria, Propniobacterium acnes. Bacteriocins are isolated, purified and dried. Morphological and general phenotypic tests are performed for identification of microorganisms. Effect of temperature, pH and bile salts on efficacy of bacteriocins is studied. Antimicrobial activity of bacteriocins is tested against the indicator strain by disc diffusion method. Normal sterile saline is used as a negative control and clindamycin is taken as a positive control. MRS media is used for culturing of microorganisms. Antimicrobial activity is recorded in terms of zone of inhibition in mm.
 Results: The isolates obtained from curd belongs to the lactobacillus family is proved by the usual phenotypic tests. Among the seven isolates obtained from curd, bacteriocins produced from isolate 6 shows maximum antimicrobial activity. Bacteriocins are most stable at pH range of 5-6 and temperature of 25-40°C. Activity decreases with increase in concentration of bile salts and completely diminishes at 11% bile salt concentration.

Antimicrobial activity of bacteriocin like inhibitory substance (BLIS) and lactic acid bacteria (LAB) isolated from traditional fermented buffalo milk from West Sumatra, Indonesia

Food preservation by chemical preservatives addition is not recommended in large quantities. However, lactic acid bacteria (LAB) metabolites can be used as a safe alternative. LAB can produce a type of antimicrobial peptide known as bacteriocin. One source of LAB that can be used as a bacteriocin-producing candidate is dadih, a traditional fermented buffalo milk product from West Sumatra, Indonesia. In this study, eight bacterial isolates isolated from dadih were identified using the catalase test and Gram straining and obtained 6 isolates that were taken as LAB. An antimicrobial activity test was carried out using the diffusion method on LAB liquid isolates suspension and crude bacteriocins from the six isolates. The isolates with the highest antimicrobial activity were DK8, the diameter of inhibiting zone of liquid isolates was 15.75 mm (Salmonella sp.), 14.25 mm (Escherichia coli), and 12.25 mm (Staphylococcus aureus). Meanwhile, the diameter of crude bacteriocin inhibition of DK 8 isolates was 8 mm (Salmonella sp.). 8 mm (E. coli), and 8.5 mm (S. aureus). Furthermore, 16S rRNA sequencing confirmed DK8 as Lactobacillus pentosus.

Study of the Antimicrobial Activity of Bacteriocins Produced by Lactic Bacteria Isolated from Camel Milk in Southern Algeria

Study of the Antimicrobial Activity of Bacteriocins Produced by Lactic Bacteria Isolated from Camel Milk in Southern Algeria

Purification and Partial Characterization of Bacteriocin Lac-B23, a Novel Bacteriocin Production by Lactobacillus plantarum J23, Isolated From Chinese Traditional Fermented Milk.

The exploration and evaluation of bacteriocin-producing lactic acid bacteria (LAB) have been one of the powerful means to food preservation. A total of 300 strains were isolated from Chinese traditional fermented milk products. A bacteriocin-producing LAB, named Lactobacillus plantarum J23, was screened and identified. Bacteriocin Lac-B23 from L. plantarum J23 was purified by 80% ammonium sulfate precipitation, cation-exchange chromatography, and reverse-phase high-performance liquid chromatography. Molecular weight of bacteriocin Lac-B23 was determined to be approximately 6.73 kDa by tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and it was confirmed as a novel bacteriocin by liquid chromatography-mass spectrometry. Moreover, bacteriocin Lac-B23 showed thermal stability when heated at below 100°C for 30 min, pH stability between pH 2.0 and 12.0, and sensitivity to trypsin, proteinase K, and proteinase E. The antimicrobial activity of bacteriocin could be enhanced by addition of Fe2+, Mn2+, and ethyl alcohol, and inhibited by Cu2+, K+, Ca2+, Zn2+, Mg2+, and sodium chloride. The results suggested bacteriocin Lac-B23 to have potential application prospects in the food industry.

Bacteriocin from Streptococcus salivarius optimized statistically by response surface methodology active against different clinical oral pathogenic Streptococci

The aim of the present work was to study the possibility of producing an effective bacteriocin from bacteria naturally exists in the mouth. Streptococcus salivarius KA101 was selected among 120 oral isolates collected from healthy people based on its ability to produce an effective bactericidal bacteriocin. Modified tryptic soy agar with 2% yeast extract and 0.1% calcium carbonate was the best medium for the production of bacteriocin with an activity of 40 AU/ml. Response surface methodology (RSM) based on central composite design (CCD) was employed to build a model in order to evaluate the optimum effective factors for bacteriocin production using four factors: yeast extract, CaCO3, pH and incubation time. Based on the optimization plot generated by RSM, the suggested optimal concentrations of yeast extract and CaCO3, as well as pH and incubation time for maximum bacteriocin production (80.2 AU/ml), were 13 g/l, 1.4 g/l, 7 and 24 hrs respectively. The results showed that bacteriocin was active for 30min at 20, 30 and 40˚C while 50% of its activity was lost at 50˚C. In addition, maximum bacteriocin activity was observed at pH 6 and 7 for 30min and disappeared completely at pH 4 and 9. Moreover, bacteriocin activity was completely lost after 90min of incubation with trypsin and pepsin which confirm its protein nature. Antimicrobial activity of bacteriocin was tested against 47 clinical isolates collected from patients suffering from different dental diseases. The results showed that the bacteriocin had an inhibitory activity against different isolates of S. mitis, S. mutans, S. oralis and Enterococcus.

Lactobacillus paracasei BK57 균주로 발효시킨 프레쉬 치즈의 항리스테리아 활성

This study is focused on establishing the optimal conditions to enhance the production of antilisterial substances by Lactobacillus paracasei BK57 isolated from Baikkimchi. In addition, the growth and in situ lactic acid and bacteriocin production of this strain were investigated during the manufacture of fresh cheese. And then the efficacy of using Lactobacillus starter as a protective culture to improve the safety of fresh cheese against Listeria monocytogenes KCTC 3569 was estimated. Maximum growth rate and activity of antibacterial substances were obtained in Lactobacilli MRS broth at 37°C with controlled pH 6.0 after 30 h of incubation under aerobic condition. However, the growth rate and antimicrobial activity of bacteriocin produced in whole milk supplemented with yeast extract (2.0%) as a substrate were lower than those obtained in MRS broth. Live cells and cell-free culture supernatant of BK57 strain were effective in the suppression of L. monocytogenes in milk, whereas the inhibitory of the bacteriocin obtained from BK57 strain was higher in BHI broth than in milk. During storage at 4°C and 15°C for 6 days, no significant difference was found in the cell viability and antimicrobial activity of BK 57 strain in fresh cheese. In samples held at two temperatures, there was at least a 15% reduction in the numbers of the pathogen in fresh cheese artificially contaminated with approximately 10 5 CFU/ml of L. monocytogenes within 6 days. Our results demonstrated the usefulness of L. paracasei BK57 having antilisterial activity as a biopreservative in the cheese making process.

In vitro Characterization of Bacteriocin Produced by Lactic Acid Bacteria Isolated from Nem Chua, a Traditional Vietnamese Fermented Pork.

The aim of this study was to screen and In vitro characterize the properties of bacteriocin produced by lactic acid bacteria isolated from Vietnamese fermented pork (Nem chua). One hundred and fifty LAB were isolated from ten samples of Nem chua and screened for bacteriocin-producing lactic acid bacteria. Antimicrobial activity of bacteriocin was carried out by spot on lawn method against both gram positive and gram negative bacteria. One isolate, assigned as KL-1, produced bacteriocin and showed inhibitory activity against Lactobacillus sakei, Leuconostoc mesenteroides and Enterococcus faecalis. To characterize the bacteriocin-producing strain, optimum temperature, incubation period for maximum bacteriocin production and identification of bacteriocin-producing strain were determined. It was found that the optimum cultivation temperature of the strain to produce the maximum bacteriocin activity (12,800 AU/mL) was obtained at 30℃. Meanwhile, bacteriocin production at 6,400 AU/mL was found when culturing the strain at 37℃ and 42℃. The isolate KL-1 was identified as L. plantarum. Antimicrobial activity of cell-free supernatant was completely inhibited by proteolytic enzyme of trypsin, alpha-chymotrypsin and proteinase K. Bacteriocin activity was stable at high temperature up to 100℃ for 10 min and at 4℃ storage for 2 d. However, the longer heating at 100℃ and 4℃ storage, its activity was reduced.

Antimicrobial potential of Lactococcus lactis bacteriocin against Salmonella typhi

Bacteriocins are natural antimicrobial peptides with potential applications in human health care and exhibit a bactericidal mode of action against different microorganisms. The present study was carried out to observe lactic acid bacteria prevalence in milk and to determine the antimicrobial activity of Lactococcus lactis bacteriocin against Salmonella typhi. Isolation and characterization of lactic acid bacteria was carried out on the basis of morphological, physiological and biochemical tests. Cell free extracts of bacteriocins were prepared by the ammonium sulphate precipitation. Antimicrobial activity was performed by Disc Diffusion method by using different organic solvents. It was observed that the genusLactococcus was common (75%) in different milk samples. Antimicrobial activity of bacteriocin was increased in different solvents. Antimicrobial activity was maximum (17.0 ± 0.7 mm) at 90:10 bacteriocin and ethanol ratio, on the other hand it was minimum (8.5 ± 0.5 mm) at 25:75 bacteriocin and ethanol ratio at pH 6.0. It was stable at higher temperature (100°C for 60 min). Sensitivity test confirmed that bacteriocin lost its activity after treating with proteinase K (0.1 mg/ml). Key words: Bacteriocin, lactic acid bacteria, Lactococcus lactis, Salmonella

Isolation and evaluation of antibacterial activity of bacteriocin produced by Lactobacillus bulgaricus from yogurt

Lactic acid bacteria (LAB) commonly used in food, as starter cultures are known to produce antimicrobial substances such as bacteriocins and have great potential as food bio-preservatives. Yogurt is a probiotic dairy product having Lactobacillus bulgaricus as natural source for fermentation. The aim of this study was to determine the antimicrobial activity of bacteriocin, produced by Lactobacillus bulgaricus isolated from yogurt and tested against pathogenic organisms. The identification of the culture was based on characteristics of the strains of Lactobacillus spp. on the basis of microscopy (morphology), Gram straining, growth at 37 and 45°C, fermentation of different carbohydrate sources and growth in MRS broth. On the basis of all of the identification tests, one strain isolated from the yogurt was identified as L. bulgaricus. Culture supernatants were obtained from the sixty out of hundred isolates of Lactobacillus spp. exhibited varying degrees of inhibitory activity against strains of Bacillus subtilis, ATCC #6633, Escherichia coli, ATCC, #10536, Salmonella typhi, ATCC# 19430,Staphylococcus aureus, ATCC #6538, Vibrio cholerae, ATCC #25870. Specifically, Vibrio cholerae was found most sensitive to bacteriocin, exhibiting maximum zone of inhibition 18.3 mm. Key words: Lactic acid bacteria (LAB), Lactobacillus bulgaricus, bacteriocin, yogurt, antimicrobial activity, Pakistan.