Bacteriocin Research Articles

Strength in Numbers: Density-Dependent Volatile-Induced Antimicrobial Activity by Xanthomonas perforans.

For most of the 20th century, Xanthomonas euvesicatoria was the only known bacterium associated with bacterial spot of tomato in Florida. X. perforans quickly replaced X. euvesicatoria, mainly because of production of three bacteriocins (BCNs) against X. euvesicatoria; however, X. perforans outcompeted X. euvesicatoria even when the three known BCNs were deleted. Surprisingly, we observed antimicrobial activity against X. euvesicatoria in the BCN triple mutant when the triple mutant was grown in Petri plates containing multiple spots but not in Petri plates containing only one spot. We determined that changes in the headspace composition (i.e., volatiles) rather than a diffusible signal in the agar were required for induction of the antimicrobial activity. Other Xanthomonas species also produced volatile-induced antimicrobial compounds against X.euvesicatoria and elicited antimicrobial activity by X. perforans. A wide range of plant pathogenic bacteria, including Clavibacter michiganensis subsp. michiganensis, Pantoea stewartii, and Pseudomonas cichorii, also elicited antimicrobial activity by X. perforans when multiple spots of the species were present. To identify potential antimicrobial compounds, we performed liquid chromatography with high-resolution mass spectrometry of the agar surrounding the spot in the high cell density Petri plates where the antimicrobial activity was present compared with agar surrounding the spot in Petri plates with one spot where antimicrobial activity was not observed. Among the compounds identified in the zone of inhibition were N-butanoyl-L-homoserine lactone and N-(3-hydroxy-butanoyl)-homoserine lactone, which are known quorum-sensing metabolites in other bacteria.

Optimization of Bacteriocin Production by Lactobacillus fermentum Strain COE20 from Fermenting Pentaclethra macrophylla Benth Using Response Surface Methodology

This study evaluated the effect of varied culture conditions (Temperature, pH, and Sodium Chloride concentration) on bacteriocin production by Lactobacillus fermentum strain COE20 isolated from fermenting African oil bean seeds (Pentaclethra macrophylla Benth) using Response Surface Methodology (RSM). A Central Composite Design (CCD) was adopted with the interest of estimating the optimal conditions for its production using the response surface regression model, which estimated the linear, squared, and interactive relationship between the response variables. The Analysis of Variance (ANOVA) showed that the coefficient of determination in terms of predicted R2 was 0.8697 which was in close agreement with an adjusted R2 of 0.7393 and was accounted for by the predictors suggesting that the model was adequate. Optimal culture condition for bacteriocin production by L. fermentum strain COE20 was found at approximately 31°C, pH 5.9, 1.9% NaCl concentration at Y = 11.75mm. Y represents the response (zone of inhibition) against Staphylococcus aureus ATCC 19095 using the agar well diffusion assay method.

Co-production of parabiotic metabolites by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12 in dairy effluents

In this study, the effects of initial pH (5 − 7), temperature (30 − 38 ◦C) and incubation time (12 − 48 h), as well as yeast extract and free linoleic acid concentrations, respectively (0 – 4 %) and (0 − 400 µL), on the co-production of conjugated linoleic acid (CLA), exopolysaccharides (EPSs) and bacteriocins (BACs) by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12 and their biomass in cheese whey and milk permeate were evaluated. The results showed that biomass, CLA, EPSs and BACs activity ranged Log 0.80 - Log 8.67 g.L-1, 3.08-107.95 µg.mL-1, 107.75-351.92 mg.L-1 and 9.29-14.62 mm, respectively. Yeast extract concentration was the only factor with the positive significant effect on biomass and parabiotic metabolites i.e. its increasing caused to an increase in both of them (p <0.05). The temperature significantly affected the production of biomass and CLA; its increasing resulted in increasing both (p <0.05). The initial pH had significant, but different, effects on EPSs and BACs production (p <0.05) i.e. EPSs and BACs production decreased and increased, respectively, as a result of increased initial pH. Increasing free linoleic acid concentration from 0 up to 400 µL led to increased CLA biosynthesis. Higher biomass, EPSs and BACs are produced in cheese whey, compared with milk permeate, but CLA produced in milk permeate was higher than that obtained in cheese whey. B. animalis BB12 produced more biomass, CLA and EPSs in comparison to L. acidophilus LA5. However, these probiotics had no statistical difference in terms of producing BACs. This work successfully demonstrated the co-production potential of CLA, EPSs and BACs by two commercial probiotics in dairy effluents.

Fermentation Optimization for Co-production of Postbiotics by Bifidobacterium lactis BB12 in Cheese Whey

Bioactive molecules, with health-beneficial effects and functional activity on the human, are called “postbiotics”, produced by probiotic bacteria. In this study, co-production of conjugated linoleic acid (CLA), exopolysaccharides (EPSs), and bacteriocins (BACs) by Bifidobacterium lactis BB12 in supplemented cheese whey was optimized using Box–Behnken design. Yeast extract concentration had a significant effect on all responses except EPSs. The temperature significantly affected the production of CLA and the inhibition zone (p < 0.05). The incubation time had significant effects on CLA, EPSs, and BACs production (p < 0.05). Desirability functions performed to the optimization of multiple responses by maximization of CLA, EPSs and inhibition zone. Optimum conditions of CLA, EPSs, and BACs co-production were as follows: incubation temperature 38 °C, incubation time 28 h, and yeast extract concentration 2.5%. Fourier transform infrared spectroscopy was used to analyze functional groups of postbiotics. Gas chromatography, thin-layer chromatography, and SDS-PAGE were used to analyze CLA isomers, EPSs monosaccharides composition, and BACs molecular weight, respectively. Co-production of CLA, EPSs, and BACs by B. lactis BB12 in dairy effluent, as a cultivation medium, optimized successfully in this study.

Optimization of food-grade medium for co-production of bioactive substances by Lactobacillus acidophilus LA-5 for explaining pharmabiotic mechanisms of probiotic.

This study aimed to optimize the co-production of conjugated linoleic acid (CLA), exopolysaccharides (EPSs) and bacteriocins (BACs) by Lactobacillus acidophilus LA-5 in dairy food-grade by-product. The factorial design revealed that the significant factors were temperature, time, and yeast extract. Then the response surface methodology was used for optimization. At the optimal conditions the viable cell number, CLA, EPSs, and inhibition activity were 2.62 ± 0.49 × 108CFU/mL, 51.46 ± 1.50μg/mL, 348.24 ± 5.61mg/mL and 12.46 ± 0.80mm, respectively. FTIR, GC, TLC, and SDS page analysis revealed the functional groups of pharmabiotics. The FTIR, GC, TLC, and SDS page analysis showed that both CLA isomers (c-9, t-11, and t-10, c-12) produced. The FTIR, GC, TLC, and SDS page analysis indicated that produced EPSs were composed of glucose, mannose, galactose, xylose, and fructose. FTIR, GC, TLC, and SDS page used to report BACs molecular weight, which showed two fractions by molecular mass 35 and 63kDa. Previously the ability of different probiotic bacteria investigated and optimized the production of CLA, EPSs, and BACs, but, there was no report on the co-producing capacity of these bioactive metabolites by probiotics. The present work was investigated to optimize the co-production of pharmabiotic metabolites by L. acidophilus LA-5, in supplemented cheese whey as a cultivation medium.

Ornithine monooxygenase and RNase J family beta-CASP ribonuclease. Can they be bacteriocins?

Ornithine monooxygenase and RNase J family beta-CASP ribonuclease. Can they be bacteriocins?

EFFECTS OF PECTIN-BASED EDIBLE COATINGS CONTAINING A BACTERIOCIN OF BACILLUS METHYLOTROPHICUS BM47 ON THE QUALITY AND STORAGE LIFE OF FRESH BLACKBERRIES

The aim of the current research is to investigate the effects of edible coatings based on celery pectin singly and in combination with a bacteriocin of Bacillus methylotrophicus BM47 on the quality and storage life of fresh blackberries under refrigeration conditions. In this study three experimental groups were prepared: uncoated blackberries as a control, blackberries with 1% pectin coatings and blackberries with 1% pectin coatings+bacteriocin of B. methylotrophicus BM47. During the storage at 4°C and 75% RH for 16 days, the weight loss, decay percentage, total soluble solids (TSS), titratable acidity (TA), pH, organic acids, sugars, total phenolic content, total anthocyanins and antioxidant activity were analyzed. The results showed that the application of pectin and pectin+bacteriocin coatings led to a reduction in weight loss with 6.3% and 6.7% compared to the control fruit on the 16-th day of storage. A decrease in decay percentage was also noticed, which was most pronounced in the pectin+bacteriocin coated fruit compared to the pectin coatings and control. The pectin and pectin+bacteriocin coatings reduced TSS levels with 0.4% and 0.6%, respectively compared to the control on the 16-th day of the storage, but did not affect TA and pH values. The pectin and pectin+bacteriocin coatings had no effect on decreasing total phenolic and anthocyanin contents or the concentration of sugars (glucose and fructose) in both treatments and the control fruit. The pectin and pectin+bacteriocin edible coatings exhibited a protective effect on the ascorbic acid content, maintaining concentrations of 57.5 mg/100 g of fw and 58.8 mg/100 g of fw (day 16), which were close to the initial values. The pectin and pectin+bacteriocin treatments had also a positive impact on antioxidant activity in the coated blackberries. Both edible coatings effectively inhibited its decrease with the prolongation of the storage time and kept antioxidant levels of 231.8 TE/100 g of fw and 232.4 TE/100 g of fw (day 16) that were close to the initial values.

Antibacterial Activity of Lactobacillus plantarum CRL 759 Against Methicillin-Resistant Staphylococcus aureus and Pseudomonas aeruginosa

Fil: Layus, Barbara Ivana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tucuman. Centro de Referencia para Lactobacilos; Argentina

Probiotics Lactobacillus strains: A promising alternative therapy against to biofilm-forming enteropathogenic bacteria?

Biofilms formation stands out in context of persistent intestinal infections caused by Enterobacteriaceae, which are associated with a high resistance to antimicrobial agents’ and phagocytosis by host defense cells. Hence, understanding the mechanisms involved in this process becomes major for the development of new preventive and therapeutic strategies. Lactic acid bacteria, including species of the genus Lactobacillus, have been associated with the prevention or dispersion of biofilms formed by pathogenic microorganisms. This effect is often associated with the antimicrobial substances production, among them organic acids, bacteriocins, hydrogen peroxide and biorsurfactants. However, the antibiofilm action of Lactobacillus seems to be strain-specific and may not be demonstrated by strains of the same genus. Thus, diet supplementation with beneficial microorganisms represents a possible strategy for prevention and treatment of intestinal infectious diseases, such as persistent or acute diarrhea caused by enteropathogenic bacteria. However, in vitro and in vivo further studies are needed to clarify the efficacy of different probiotic candidates, including commercially available products. Keyword: Enterobacteria, biofilm, lactobacillus, antimicrobials.

In vitro assessment of Leuconostoc mesenteroides zinc nanoparticles against Salmonella serovars recovered from broilers chickens

Salmonella serovars are responsible for a variety of acute and chronic diseases in poultry. Leuconostoc mesenteroides probiotic can exert antimicrobial activity by producing diverse fermentative metabolites with bactericidal or bacteriostatic activities such as lactic and acetic acids, fatty acids, hydrogen peroxide or diacetyl and antimicrobial proteins such as bacteriocins and peptidoglycan hydrolase enzymes. This trial aimed at adding novel therapy against virulent and multidrug resistance avian salmonellosis. The incidence of salmonellae in this study was 20% with high recovery rate from liver followed by yolk sac and the most common serovars were Salmonella Kentukey, Salmonella Infantis and Salmonella Enteritidis whose antibiogram showed high resistance to ampicillin, nalidexic acid, sulphamethoxasole + trimethoprim and tetracyclines. Selected virulent and multidrug resistant Salmonella serovars were exposed to probiotic mixture consisting of L. mesenteroides and zinc nanoparticles in different concentration to detect the antibacterial effect against different Salmonella serovars as novel therapy for avian salmonellosis. This study revealed that green synthesis of zinc nanoparticles by using L. mesenteroides biodegradation 100 nm in size and 10 µg/ml in concentration has potent inhibitory effect against broad range of Salmonella serovars but its salmonicidal effect occurred only at 2000 µg/ml. Key words: Broilers chicken, Salmonella, Leuconostoc mesenteroides, zinc nanoparticles.

DETERMINATION OF THE INTENSITY OF BACTERIOCIN PRODUCTION BY STRAINS OF LACTIC ACID BACTERIA AND THEIR EFFECTIVENESS

DETERMINATION OF THE INTENSITY OF BACTERIOCIN PRODUCTION BY STRAINS OF LACTIC ACID BACTERIA AND THEIR EFFECTIVENESS

Antioxidant and antimicrobial activity of bacteriocin-producing strains of lactic acid bacteria isolated from the human gastrointestinal tract

Background: cancer patients require special attention to maintenance therapy of their organism vital activity. Distribution of nutritional deficiency in cancer patients not only limits the possibilities of application of modern treatment methods, but can also be the direct cause of life-threatening complications and premature death. Objective: to study the use of bioactive peptide complexes with low molecular weight and probiotic strains isolated from the human gastrointestinal tract in food products intended for patients with cancer during their treatment and rehabilitation. Material and Methods: 14 strains of lactic acid bacteria were pre-selected and identified for this study. They were allocated from the gastrointestinal tract of 500 healthy people and people with cancer, who presented different age groups. The study of antagonistic activity of lactic acid bacteria was carried out by using the MRS medium and Lysogeny broth (LB). Biocompatibility study was performed through the co-culture method on solid MRS medium. Results: Research results proved that the isolated metabolites belonged to bacteriocins, as the studied microorganisms were resistant both to their inhibitors and mutually resistant to the single-type synthesized substances. Conclusions. Probiotics have a positive effect on the immune system, as the gastro-intestinal flora they reduce the impact of mutagens and carcinogens.

Determination of Bacteriocin Genes and Antibacterial Activity of Lactobacillus Strains Isolated from Fecal of Healthy Individuals.

Lactobacillus species play a major role in gastrointestinal (GI) tract function, intestinal microbiota balance, and the immune system activity by exerting a strong activity against many intestinal pathogens. The aim of this study was to isolate Lactobacillus species from fecal samples, investigate their antimicrobial properties, and characterize their bacteriocin encoding genes. 48 fecal samples were grown in MRS broth and then MRS agar. The colonies grown in MRS agar were selected and identified by PCR. 72 Lactobacillus species were obtained from 434 lactic acid bacteria (LAB) strains. Approximately 40% of all Lactobacillus isolates had antimicrobial activity against one or more microorganisms and 17.4% of them were active against all four indicator bacteria. The frequency of bacteriocin encoding genes were 5 (6.9%), 3 (4.1%) and 5 (6.9%) for Gassericin A, Plantaricin S and Laf operon, respectively. pH alteration had no effect on antibacterial activity, but in the alkaline range these activities were reduced and the strains showed the highest antibacterial activity after 48 h incubation. These data indicate that the majority of isolates were susceptible to GI tract or belonged to other bacterial forms such as viable but nonculturable (VBNC). The detection of bacteriocin encoding genes in about only 6% of all Lactobacillus isolates seems to be due to the existence of many other bacteriocin encoding genes in Lactobacillus species which were not tested. Further study of the bacteriocin gene clusters, types, subtypes and the probiotic effect of these strains will contribute to a better characterization of these isolates.

Selection of lactic acid bacteria producing bacteriocin

Lactic acid bacteria were isolated from 10 samples of the traditionally fermented foods (5 samples of Vietnamese fermented pork roll and 5 samples of the salted field cabbage) and 5 samples of fresh cow milks collected from households in Vietnam. 22 strains of lactic acid bacteria were isolated for inhibition to Lactobacillus plantarum JCM 1149. Of these, only 2 strains including DC1.8 and NC1.2 have rod shape, the others have coccus shape. 7 strains showing higher antibacterial activity were selected for checking spectrum of antibacteria with indicator bacteria consistting of Bacillus subtilis ATCC 6633, Enterococcus faecium JCM 5804 and Staphylococcus aureus TLU. By which, 3 strains including NC3.5 (from Vietnamese fermented pork roll), DC1.8 (from salted field cabbage) and MC3.19 (from fresh cow milk) were selected because of their higher antibacterial ability. However, the antibacterial activity of the lactic acid bacteria can be based on their disposable compounds and some other antibacterial compounds produced during their growth (such as lactic acid, H2O2, bacteriocins, etc.). For seeking lactic acid bacteria with capability of producing bacteriocins, antibacterial compounds with protein nature, 3 above strains were checked sensitiveness to proteases (including protease K, papain, α – chymotrypsin and trypsin). Because bacteriocins are proteinaceous antibacterial compounds, so their antibacterial activity will be reduced if proteases are added. The result showed DC1.8 and MC3.19 were capable of producing bacteriocin during culture process. They were identified as Lactobacillus acidophilus and Lactococcus lactis and classified, respectively, based on analysis chemical characterisitcs by standard API 50 CHL kit and phylogeny relationship by 16s rRNA sequences.&#x0D; Các chủng vi khuẩn lactic được phân lập từ 10 mẫu thực phẩm lên men truyền thống (5 mẫu nem chua, 5 mẫu dưa cải bẹ muối) và 5 mẫu sữa bò tươi được thu thập từ các hộ gia đình ở Việt Nam. 22 chủng vi khuẩn lactic đã được phân lập với tiêu chí có khả năng kháng lại vi khuẩn kiểm định Lactobacillus plantarum JCM 1149. Trong số đó, 2 chủng DC1.8 và NC1.2 có tế bào hình que, các chủng còn lại có tế bào hình cầu. 7 chủng thể hiện hoạt tính kháng khuẩn cao được lựa chọn để xác định phổ kháng khuẩn rộng hơn với ba loài vi khuẩn kiểm định Bacillus subtilis ATCC 6633, Enterococcus faecium JCM 5804 và Staphylococcus aureus TLU. Từ đó lựa chọn được 3 chủng có hoạt tính kháng khuẩn cao hơn hẳn. Các chủng này gồm NC3.5 phân lập từ nem chua, DC1.8 phân lập từ dưa cải bẹ muối và MC3.19 phân lập từ sữa bò tươi. Tuy nhiên, hoạt tính kháng khuẩn của vi khuẩn lactic bao gồm những hợp chất nội tại có trong nó và cả những hợp chất được sinh ra trong quá trình phát triển của nó (như axit lactic, H2O2, bacteriocin, …). Với định hướng tìm chủng vi khuẩn lactic có khả năng sinh bacteriocin, chất kháng khuẩn có bản chất protein, 3 chủng trên được kiểm tra độ nhạy cảm với các protease (gồm protease K, papain, α – chymotrypsin và trypsin). Do bacteriocin là chất kháng khuẩn có bản chất protein nên hoạt tính kháng khuẩn của chúng sẽ bị giảm nếu protease được bổ xung vào. Kết quả lựa chọn được chủng DC1.8 và MC3.19 có khả năng sinh bacteriocin. Hai chủng này được phân loại đến loài nhờ vào phân tích đặc điểm sinh hóa bằng kit API 50 CHL và mối quan hệ di truyền thông qua trình tự gen 16s rRNA. Kết quả phân loại đã xác định chủng DC1.8 thuộc loài Lactobacillus acidophilus và chủng MC3.19 thuộc loài Lactococcus lactis.

Effect of supplementation of yeast with bacteriocin and Lactobacillus culture on growth performance, cecal fermentation, microbiota composition, and blood characteristics in broiler chickens.

ObjectiveThe aim of the present study was to investigate the effect of yeast with bacteriocin and Lactobacillus cultures (mixture of Lactobacillus agilis BCRC 10436 and Lactobacillus reuteri BCRC 17476) supplements, alone or in combination, on broiler chicken performance.MethodsA total of 300, 1-d-old healthy broiler chickens were randomly divided into five treatment groups: i) basal diet (control), ii) basal diet+0.25% yeast (Saccharomyces cerevisiae) (YC), iii) basal diet+0.25% yeast with bacteriocin (BA), iv) basal diet+Lactobacillus cultures (LAB), and v) basal diet +0.25% yeast with bacteriocin+Lactobacillus cultures (BA+LAB). Growth performance, cecal microbiota, cecal fermentation products, and blood biochemistry parameters were determined when chickens were 21 and 35 d old.ResultsThe supplementation of YC, BA, and BA+LAB resulted in a significantly better feed conversion rate (FCR) than that of the control group during 1 to 21 d (p<0.05). The LAB supplementation had a significant effect on the presence of Lactobacillus in the ceca at 35 d. None of the supplements had an effect on relative numbers of L. agilis and L. reuter at 21 d, but the BA supplementation resulted in the decrease of both Lactobacillus strains at 35 d. The BA+LAB supplementation resulted in higher short chain fatty acid (SCFA) in the ceca, but LAB supplementation significantly decreased the SCFA at 35 d (p<0.05). All treatments tended to decrease ammonia concentration in the ceca at 21 d, especially in the LAB treatment group. The BA supplementation alone decreased the triacylglycerol (TG) concentration significantly at 21 d (p<0.05), but the synergistic effect of BA and LAB supplementation was required to reduce the TG concentration at 35 d. The YC supplementation tended to increase the plasma cholesterol at 21 d and 35 d. However, the BA supplementation significantly decreased the cholesterol and low density lipoprotein cholesterol level at 35 d. In conclusion, the BA+LAB supplementation was beneficial to body weight gain and FCR of broiler chickens.ConclusionThe effect of BA and LAB supplementation may be a result of the growth of lactic acid bacteria enhancement and physiological characterization of bacteriocin, and it suggests that the BA and LAB supplementation level or Lactobacillus strain selection should be integrated in future supplementation designs.

Bacteriocin Profiling of Probiotic Lactobacillus spp. Isolated from Yoghurt

Bacteriocin producing Lactobacillus spp. isolated from yoghurt, showed wide range of antimicrobial activity against some major food borne pathogens. Antimicrobial assay was conducted by modified agar overlay method and well diffusion method. Isolate 3 showed highest (42 mm) antimicrobial activities and isolate 4 showed lowest (15 mm) antimicrobial activities against test organisms. Bacillus subtilis showed the highest and Staphylococcus aureus showed the least susceptibility to the bacteriocins of isolated Lactobacillus spp. Cell extract & culture supernatant of isolates also showed antimicrobial activity. Bacteriocins were isolated from cell lysate of Lactobacillus spp. & separated by SDS-PAGE. All the isolates produced bacteriocins of 94 kDa, 60 kDa & 45 kDa molecular weight intracellularly& crude extracts of these bacteriocins showed considerable antimicrobial activity against test pathogens. This study revealed the possibility of bacteriocin as bio-preservatives for food stuffs.

Spectrum of antimicrobial activity of lactic acid bacteria (Lactobacillus KSBT 56) isolated from indigenous fermented products of Odisha

The strain KSBT56 was isolated from a traditional fermented product ‘dahi chhenna’ of Odisha by pour plate method on MRS agar. Biochemical and 16s rDNA sequencing confirmed KSBT 56 as genus Lactobacillus. The cell-free supernatants (CFS) ofLactobacillus KSBT56 demonstrated an antibacterial activity against a wide range of Gram-negative and Gram-positive pathogens (Escherichia coli MTCC 82, Bacillus cereus ATCC10702, Salmonella spp. (Salmonella enteritidis 125109, Salmonella enterica serovar typhi MTCC 3216, Salmonella typhimurium SB300), Aeromonas hydrophila ATCC 7966, and Staphylococcus aureus MTCC 96. In contrast, it did not inhibit any lactobacilli tested. The putative metabolite produced by this organism was heat stable, sensitive to various pH values, a low molecular mass (<3000 Da) and either insensitive or low level sensitive to enzymatic treatments and require an acidic condition to develop. The compound resembles defensin more closely rather than bacteriocin and microcin. Key words: Lactic acid bacteria, antibacterial activity, indigenous product, bacteriocin, microcin, defensin.

Media Optimization of Bacteriocin ST22Ch Production by Lactobacillus Sakei ST22Ch Isolated from Salpicão, a Traditional Meat-Product from Portugal

Bacteriocins are known for anti-microbial properties against various pathogens. In the present study, bacteriocin ST22Ch produced by Lactobacillus sakei isolated from salpicao, a traditional pork product from the northwest of Portugal, inhibited the growth of Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae, Lactobacillus rhamnosus, Listeria ivanovii subsp. ivanovii, Listeira monocytogenes, Pseudomonas spp., Staphylococcus aureus, Streptococcus caprinus and Streptococcus spp. In particular, low levels of bacteriocin ST22Ch activity (approximately 200 AU/mL) was detected after 3 h of growth in MRS broth. Maximal production (1600 AU/mL) of bacteriocin ST22Ch was recorded after 19 h in MRS broth, stay constant only for 5 h and decrease to 800 AU/mL and only when incubated at 30 °C. During 35 h of growth, the optical density increased from 0.15 to 5.73. Highest bacteriocin ST22Ch production (3200 AU/mL) was records in presence of yeast extract as single organic nitrogen source (20.0 g/L). Presence of tryptone (20.0 g/L) or combination of tryptone and meat extract (12.5 g/L and 7.5 g/L) or yeast extract and meat extract (10.0 g/L and 10.0 g/L, respectively) yielded 1600 AU/mL bacteriocin production. Presence of glycerol at 1.0 g/L to 5.0 g/L not effect the bacteriocin ST22Ch production. Tween 80 added to the MRS medium (5.0 g/L) increase bacteriocin ST22Ch production up to 6400 AU/mL. Exclusion of manganese sulphate results in reduction of activity in the cell-free supernatant. Exclusion of magnesium sulphate from the media formula increases the bacteriocin production to 3200 AU/mL.

Detection of Heat Stable Bacteriocin from Lactobacillus acidophilus NCIM5426 by Liquid Chromatography/mass Spectrometry

Bacteriocins from lactic acid bacteria (LAB) are natural antimicrobial peptides or proteins with interesting potential applications in food preservation and health care. The present study was aimed to isolate bacteriocinogenic LAB from dairy products, fermented food and environmental waste samples. One thirty five colonies of LAB were isolated and screened for bacteriocin production by agar overlay method. Among them, Lactobacillus acidophilus NCIM5426 isolated from home made paneer showed maximum zone of inhibition i.e 22-24mm in diameter against food borne ( Listeria monocytogenes , Staphylococcus aureus ) and human pathogens ( Escherichia coli , Salmonella typhi ). The antibacterial compound from the culture supernatant was found to be proteinaceous in nature and therefore, identified as bacteriocin. The bacteriocin of L. acidophilus NCIM5426 was found to be heat-stable (121°C for 15 min) and active over a wide pH range of 4.0-10.0. It showed stability (60%) for 30 days at room temperature (30-32°C). Addition of surfactants (EDTA, SDS, Hexadecyl trimethylamonium bromide) up to 1% to crude bacteriocin showed increase in antibacterial activity where as metal ions (Calcium Chloride, Zinc Sulphate and Mercuric Chloride) in low concentration (0.5-1mgL -1 ) decreased the activity. The bacteriocin was purified to its homogeneity by ammonium sulfate precipitation followed by gel filtration chromatography and HPLC. Molecular weight of bacteriocin was found to be 5.6 and 5.8 KDa by SDS page and LC/MS respectively. Production and activity of bacteriocin was significant (50%) even at higher salt (NaCl) concentration i.e 3%. Our present study demonstrates the possibility of using L. acidophilus NCIM5426 or its bacteriocin as a biopreservative in dairy industry.

Purification and characterization of the novel bacteriocin Bac IH7 with antifungal and antibacterial properties.

Bacillus subtilis strain IH7 was isolated from the rhizosphere of Tunisian healthy plants and selected for its antimicrobial activities against bacteria and fungi. This strain produced a novel antimicrobial peptide (bacteriocin) called Bac IH7. The pure bacteriocin was obtained after precipitation by ammonium sulphate, chromatography on Sephadex G-25 and C18 reverse-phase HPLC. The SDS-PAGE analysis of purified Bac IH7 revealed a single band with an estimated molecular mass of approximately 14 kDa. Bac IH7 was sensitive to various proteases, thus proving to have protein nature and displayed a wide inhibitory spectrum towards Grampositive and Gram-negative bacteria and fungal pathogens. Purified Bac IH7 exhibited a bactericidal mode of action against Agrobacterium tumefaciens C58 and a fungistatic mode of action against Candida tropicalis R2 CIP203. Interestingly, based on conventional agronomic parameters for seed vigour, the application of Bac IH7 (800 AU) showed it to be a potent exogenous enhancer of growth that enhanced the vigour of tomato and muskmelon seedlings. Compared to the control, the germination percentage, shoot weight, shoot height, and root length were all significantly enhanced in the Bac IH7-treated plant seeds. Bac IH7 also exhibited effective disinfectant properties against seedborne diseases. In treated seeds, Bac IH7 had significant effects on the control of damping-off disease groups at the pre-germination stage, of root rot caused by Alternaria solani, as well as of wilt diseases and other bacterial seed-borne pathogens.