Bacteriocin-producing Strains Research Articles

Extending the Shelf Life of Camembert Cheese via Controlling Over-Ripening by Bacteriocin of Newly Lactic Acid Bacterial Isolate LAB100

Camembert cheese is a surface white mould ripened cheese; when full ripe the casein becomes liquefy as the intensive degradation occurs by proteinases from surface flora and results over-ripening and off flavor. To control this, partial purified bacteriocin like substances (PPBLS) from newly lactic acid bacterial isolate (LAB100) exhibited antifungal activity against Penicillium candidum (in vitro) were used. Inhibition (%) of P. candidum by PPBLS at concentrations of 2, 4, 8, 16 and 32 mg/ml was 34, 50, 79, 80 and 85%, respectively. Based on their superior antifungal potential activity; isolate LAB100 was phenotypically and genotypically characterized as newly Lactobacillus sp. For delaying the Camembert cheese over-ripening (in vivo), bacteriocin producing isolate LAB100 and its PPBLS were incorporated and applied in different camembert cheese treatments. Three treatments beside control were conducted; after brining all cheese treatments stored at 12±2°C to ripen for 12 days and then at 5±2°C for more 30 days to complete ripening. Organoleptic properties, pH values and nitrogen distribution were determined during ripening period. In addition, the proteolysis of treated Camembert cheese was monitored by gel electrophoresis. The cheese treatment (T2) made with bacteriocin producer isolate LAB 100 added as co-culture to main starter recorded the highest total score, followed by T3 and the lowest one was recorded for control (T1). The highest WSN/TN% was in T1; 5.4, 22.87, 34.41 and 57.65% at 3, 10, 20, and 40 days after brining, respectively, while the lowest WSN/TN% was recorded for treatment that made with both bacteriocin producer strain LAB100 and sprayed by PPBLS solution after 3 days of brining (T3), where it was 5.05, 9.85, 13.82, and 31.74% at the same previous ages, respectively. These results were confirmed by gel electrophoresis, indicating that bacteriocin producer LAB100 and or its bacteriocin controlled the protein degradation. These results suggest that both bacteriocin producer strain and its PPBLS minimize the growth of P. candidum as a consequence the rate of proteolysis was controlled and hence extending the shelf life of Camembert cheese is occurred.

Inhibition of Listeria monocytogenes biofilms by bacteriocin-producing bacteria isolated from mushroom substrate.

This study was designed to investigate the ability of naturally occurring bacteria isolated from mushroom substrate to prevent biofilm formation by Listeria monocytogenes or to remove existing biofilms in mushroom production facilities. It is generally recognized that L. monocytogenes forms biofilms that can facilitate its survival in food-processing environments. Eleven bacteriocin-producing isolates were identified and the bacteriocins characterized based on heat and enzyme inactivation studies. Further characterization was undertaken by MALDI-TOF mass spectrometry, PCR and sequencing. Production of nisin Z (by Lactococcus lactis isolates), subtilomycin (by Bacillus subtilis isolates) and lichenicidin (by Bacillus licheniformis and Bacillus sonorensis isolates) was detected. In co-culture with L. monocytogenes, the bacteriocin-producing strains could prevent biofilm formation and reduce pre-formed biofilms. Mushroom substrate can be a source of bacteriocin-producing bacteria that can antagonize L. monocytogenes. The results highlight the potential of bacteriocin-producing strains from mushroom substrate to reduce L. monocytogenes biofilm in food production environments, contributing to a reduction in the risk of food contamination from the environment.

The Potential of Class II Bacteriocins to Modify Gut Microbiota to Improve Host Health.

Production of bacteriocins is a potential probiotic feature of many lactic acid bacteria (LAB) as it can help prevent the growth of pathogens in gut environments. However, knowledge on bacteriocin producers in situ and their function in the gut of healthy animals is still limited. In this study, we investigated five bacteriocin-producing strains of LAB and their isogenic non-producing mutants for probiotic values. The LAB bacteriocins, sakacin A (SakA), pediocin PA-1 (PedPA-1), enterocins P, Q and L50 (enterocins), plantaricins EF and JK (plantaricins) and garvicin ML (GarML), are all class II bacteriocins, but they differ greatly from each other in terms of inhibition spectrum and physicochemical properties. The strains were supplemented to mice through drinking water and changes on the gut microbiota composition were interpreted using 16S rRNA gene analysis. In general, we observed that overall structure of the gut microbiota remained largely unaffected by the treatments. However, at lower taxonomic levels, some transient but advantageous changes were observed. Some potentially problematic bacteria were inhibited (e.g., Staphylococcus by enterocins, Enterococcaceae by GarML, and Clostridium by plantaricins) and the proportion of LAB was increased in the presence of SakA-, plantaricins- and GarML-producing bacteria. Moreover, the treatment with GarML-producing bacteria co-occurred with decreased triglyceride levels in the host mice. Taken together, our results indicate that several of these bacteriocin producers have potential probiotic properties at diverse levels as they promote favorable changes in the host without major disturbance in gut microbiota, which is important for normal gut functioning.

Antilisterial active compound from lactic acid bacteria present on fresh iceberg lettuce

Pediococcus pentosaceus DT016, a bacteriocin producing strain, was isolated from fresh lettuce. A protein with antilisterial activity (bacDT016), between 11 to 17 kDa, was identified and characterized as the bioactive substance from the LAB culture. Highest bacteriocin production was noted after 15 h of growth. Antibacterial activity was affected by some enzymes and detergents, as well as by temperatures equal or above 80 ºC. DT016 strain contains an 1110 bp DNA fragment with homology to pediocin AcH/PA-1.

Bacteriocin production by Streptococcus thermophilus in complex growth media.

To test if the production of bacteriocins by Streptococcus thermophilus is influenced when grown in various complex media commonly used for the culturing of lactic acid bacteria. Forty-one strains of S. thermophilus were screened for the production of bacteriocins in tryptone/yeast extract/lactose (TYL), M17-lactose (M17L), M17-glucose (M17G) and MRS media. Two strains, ST144 and ST145, were identified as novel bacteriocin producers, with constitutive production observed only in M17G. Strains ST110, ST114 and ST134 constitutively produced bacteriocins in all growth media but ST114 required growth in MRS for its antimicrobial activity to persist in a 24h culture. The addition of a synthetic quorum sensing peptide (BlpC) induced bacteriocin production by ST106 in all media tested; and by ST118 in TYL and M17L. Strain ST109, which constitutively produced a bacteriocin in TYL and M17 broths, required BlpC induction when grown in MRS. Real-time PCR analysis showed that the natural expression of blpC in ST109 was lower when grown in MRS, suggesting that something in medium interfered with the blp quorum sensing system. As the choice of growth medium influences both bacteriocin production and peptide stability, several types of production media should be tested when screening for novel bacteriocin-producing strains of S. thermophilus.

Protection of honeybee Apis mellifera by its endogenous and exogenous lactic flora against bacterial infections

Abstract Lactic acid bacteria (LAB) symbionts of honeybees are certainly playing key roles in their host's colony functioning. The defense against bacterial pathogen invasion by endogenous LAB has been considered as promising and usable phenomenon. This study addresses bacteriocinogeny as one of antibacterial action mode displayed by bacteria. The honeybee endogenous LAB isolated from worker honeybee intestines (61 strains), queen honeybee intestines (16 strains) and beebread (25 strains) were tested for bacteriocin production ability. We checked also well characterized bacteriocin producing LAB strains against bacteria causing American foulbrood (AFB) – Paenibacillus larvae aiming possible use of exogenous LAB for control AFB in honeybees and in the same time to observe the vulnerability of endogenous bacteria exposed to bacteriocin producers. We demonstrated that none of 102 studied LAB strains, isolated from worker honeybee intestines, from queen honeybee intestines and from beebread, produced bacteriocins detectable by the well diffusion method (WDM). All of them failed to inhibit two strains of P. larvae . Three exogenous bacteriocin-producing LAB strains were tested against the same pathogens and against 25 endogenous bacterial isolates representing 11 different LAB species. The screening showed that all the tested exogenous bacteriocin-producing strains inhibited the tested P. larvae strains. The endogenous LAB strains exhibited varied sensitivity profiles when treated with bacteriocin-producing strains. This raises similar challenges to those observed in antibiotic applications leading to dysbacteriosis, even though the efficacy of these bacteriocins against P. larvae in an in vitro system is evident.

Bacteriocinogenic Potential of Enterococcus faecium Isolated from Wine.

A total of 145 lactic acid bacteria isolated from a variety of Turkish red wines during malolactic fermentation were screened to find bacteriocin-producing strains. Among them, 14 isolates of Enterococcus faecium were identified to produce bacteriocins. PCR screening revealed that some isolates harbored entA and entB genes while some harbored entA, entB and entP genes. An isolate designated as Ent. faecium H46 was selected to characterize its bacteriocins. The bacteriocins were purified to homogeneity from culture supernatant by Amberlite XAD-16, cation-exchange and reverse-phase chromatography. MALDI-TOF mass spectrometry analysis identified the bacteriocins as enterocin A and enterocin B. The presence of Ent. faecium is noteworthy since it is not associated with wine fermentation. However, it has been reported as an important wine spoilage organism due to its potential to produce tyramine. Although species of Enterococcus is not known as wine bacteria, contamination by Ent. faecium may arise from grapes or wineries equipments used for wine production.

Effect of bacteriocin-producing Pediococcus acidilactici K10 on beer fermentation

Beer is generally considered to be a beverage that has high microbiological stability. However, some undesirable lactic acid bacteria (LAB) can grow in beer and consequently spoil this beverage. In this study, bacteriocin-producing Pediococcus acidilactici K10 was used as a means of bio-acidifying the mash and reducing the spoilage LAB content of the beer. The K10 strain had antimicrobial activity against two beer spoilage LAB strains in wort and did not grow in a beer environment. The K10 strain was inoculated before the mashing step. The effect of K10 as a starter culture was investigated and compared with a control. As a result, filtration time was shortened by 17 min, alcohol content was increased by 137%, foam stability was increased by 156%, bitterness was increased by two bitterness units and there was a significant difference (p < 0.05) in aromatic and sour odour. The feasibility of using bacteriocin-producing LAB strain in beer brewing is envisaged. Copyright © 2016 The Institute of Brewing & Distilling

Mode of action of leucocin K7 produced by Leuconostoc mesenteroides K7 against Listeria monocytogenes and its potential in milk preservation.

To investigate the mode of action of leucocin K7 against Listeria monocytogenes and to assess its inhibitory effect on Lis. monocytogenes in refrigerated milk. A bacteriocin-producing strain, Leuconostoc mesenteroides K7, was isolated from a fermented pickle. The bacteriocin, leucocin K7, exhibited antagonistic activity against Lis. monocytogenes with an MIC of 28µg/ml. It was sensitive to proteaseS and displayed good thermal stability and broad active pH range. Leucocin K7 had no effect on the efflux of ATP from Lis. monocytogenes but triggered the efflux of K(+) and the intracellular hydrolysis of ATP. It also dissipated the transmembrane electrical potential completely and transmembrane pH gradient partially. It 80 AU/ml inhibited the growth of Lis. monocytogenes by 2.3-3.9 log units in milk; when combined with glycine (5mg/ml), it completely eliminated viable Lis. monocytogenes over 7days Leucocin K7 shows different mode of action from nisin and may have potential application in milk preservation.

Exploring the metabolic heterogeneity of coagulase-negative staphylococci to improve the quality and safety of fermented meats: a review

The production of fermented meats, such as fermented sausage, relies on the metabolic activities of lactic acid bacteria and catalase-positive cocci, in particular the group of coagulase-negative staphylococci (CNS). Conventional use of CNS as meat starter cultures usually leads to an appropriate cured colour development based on their nitrate reductase activity, whereas their catalase activity reduces oxidative damage. In addition, CNS metabolism contributes to flavour, although the precise effects are difficult to estimate. There are reasons to believe that these basic technological features of CNS can be further enlarged by exploring their full metabolic potential. Non-negligible differences in metabolism among and within different species of CNS indicate that a rational selection of strains may lead to the development of novel starter cultures with enhanced functionality. Firstly, the use of CNS strains with a superior ability to use alternative energy sources, such as nucleosides or arginine, may improve culture competitiveness and survival. Secondly, cured colour generation could be optimised to lower the amounts of curing salts needed, either by selecting for efficient nitrate-reducing CNS strains or by exploring the potential alternative based on nitric oxide synthase activity. Thirdly, CNS with specific aroma-producing abilities may help to accentuate specific flavours, whereby the selection of wild-type strains from artisan-type fermented sausages seems attractive in the framework of innovation-through-tradition. Finally, bacteriocin-producing CNS strains may offer solutions for bioprotection towards meat pathogens such as Clostridium botulinum and Staphylococcus aureus. Overall, making use of the metabolic inter- and intraspecies heterogeneity of CNS is promising for the elaboration of healthier, tastier, and safer fermented meats. Yet, the proposed strategies are sometimes still overly theoretical and speculative, requiring further proof-of-principle.

Control of Listeria monocytogenes biofilms on industrial surfaces by the bacteriocin-producing Lactobacillus sakei CRL1862.

The effect of the bacteriocin-producing Lactobacillus sakei CRL1862 and its bacteriocin in the control of Listeria biofilm formation on industrial surfaces at 10°C was investigated. A screening among different Listeria species was performed allowing selecting L. monocytogenes FBUNT for its use as a biofilm producer on stainless steel (SS) and polytetrafluoroe-thylene (PTFE) surfaces. Three conditions were simulated to evaluate the ability of the bacteriocinogenic strain to displace, exclude and compete pathogen biofilm formation. Lactobacillus sakei CRL1862 effectively inhibited biofilm formation by L. monocytogenes FBUNT through the three assayed mechanisms, pathogen inhibition being more efficient on PTFE than on SS surface. Moreover, co-culture of L. monocytogenes FBUNT with the bacteriocin-producer displayed the highest efficacy reducing the pathogen by 5.54 ± 0.12 and 4.52 ± 0.01 on PTFE and SS, respectively. Industrially, the pre-treatment with L. sakei CRL1862 or its bacteriocin (exclusion) constitutes the most realistic way to prevent pathogen biofilm settlement. The use of bacteriocins and/or the bacteriocin-producer strain represents a safe and environmentally-friendly sanitation method to mitigate post-processing food contamination.

A Sequential Statistical Approach Towards an Optimized Production of Bacteriocin byLactobacillus pentosusTSHS

Bacteriocins, antimicrobial compounds, display applications from food preservation to medicine. The aim of this study was the statistical optimization of a bacteriocin substance production from traditional cheese bacterium taxonomically affiliated as Lactobacillus pentosus TSHS. The effects of variables were first investigated using the Placket–Burman design. Central composite design was then used to compute incubation time and NaCl concentration optimum. Response surface methodology (RSM) revealed that maximum bacteriocin production was achieved at low NaCl concentration (0.13 mol/L) and an incubation time of 47 h. The validation experiments were implemented under optimal conditions with five replicates and the bacteriocin inhibitory activity was increased by three times. The research led to parameters that maximized pentocin activity, which can be expressed as a quadratic function of incubation time and NaCl concentration. The application of RSM resulted in an enhancement in pentocin production cost effective medium. Practical Applications Bacteriocins produced by lactic acid bacteria have been found to inhibit the growth of many foodborne microorganisms, and hence, can be used as natural preservatives to increase shelf life of food. High bacteriocin production is required for application in food industry. However, bacteriocin production does not always correlate with growth rate of bacteriocin producing strain. This study has developed appropriate conditions to give optimum yield of bacteriocin. So, it revealed the possibility of bacteriocin application as biopreservatives according to industrial point of view.

Purification and Characterization of Plantaricin JLA-9: A Novel Bacteriocin against Bacillus spp. Produced by Lactobacillus plantarum JLA-9 from Suan-Tsai, a Traditional Chinese Fermented Cabbage.

Bacteriocins are ribosomally synthesized peptides with antimicrobial activity produced by numerous bacteria. A novel bacteriocin-producing strain, Lactobacillus plantarum JLA-9, isolated from Suan-Tsai, a traditional Chinese fermented cabbage, was screened and identified by its physiobiochemical characteristics and 16S rDNA sequence analysis. A new bacteriocin, designated plantaricin JLA-9, was purified using butanol extraction, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular mass of plantaricin JLA-9 was shown to be 1044 Da by MALDI-TOF-MS analyses. The amino acid sequence of plantaricin JLA-9 was predicted to be FWQKMSFA by MALDI-TOF-MS/MS, which was confirmed by Edman degradation. This bacteriocin exhibited broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, especially Bacillus spp., high thermal stability (20 min, 121 °C), and narrow pH stability (pH 2.0-7.0). It was sensitive to α-chymotrypsin, pepsin, alkaline protease, and papain. The mode of action of this bacteriocin responsible for outgrowth inhibition of Bacillus cereus spores was studied. Plantaricin JLA-9 had no detectable effects on germination initiation over 1 h on monitoring the hydration, heat resistance, and 2,6-pyridinedicarboxylic acid (DPA) release of spores. Rather, germination initiation is a prerequisite for the action of plantaricin JLA-9. Plantaricin JLA-9 inhibited growth by preventing the establishment of oxidative metabolism and disrupting membrane integrity in germinating spores within 2 h. The results suggest that plantaricin JLA-9 has potential applications in the control of Bacillus spp. in the food industry.

EFFECT OF INOCULUM OF VIABILITY OF NONCULTURABLE CELLS OF BACTERIOCIN-PRODUCING Lactococcus lactis ssp. lactis Strains

The comparative studies on obtaining viable but nonculturable cells (VBNC) of two bacteriocin-producing strains of Lactococcus lactis ssp. lactis of different origins and activity levels under carbohydrate starvation stress have been performed. Two different types of inoculum were applied: P1, unwashed from culture liquid cells, and P2, twice washed with normal 0.9% saline cells. The P1 inoculum shifted to non-culturability faster than P2. During the whole experiment we studied changes in such strain population characteristics as total number of cells, total number of viable cells, number of colony-forming units, number of VBNC (from the nisin-producing activity), and ratio of viable to dead cells in population (using Live/Dead® (Baclight™) staining kit). After 1 year of incubation culturability decreased by 3—6 orders of magnitude in either of populations, and P1 inoculum VBNC demonstrated considerable reduction of cell size. After a year of culturing, the bacteriocin activity of P2 cells was up to 19 times higher than of P1 cells.

Genetic Characterization of Enterococcus Faecalis N1-33 Bacteriocin and Obtained of the Mutant Strain that Produce Many Bacteriocin by Novobiocin Agent Effect, its Merit as A Food Preservative in Steamed Rice Model

Enterococcus faecalis strain N1-33 produces a peptide that shows bacteriocin activity, enterocin MR10A (EntMR10A). We cloned and sequenced the structural gene of the EntMR10A locus (entMR10A), and the peripheral region of entMR10A was analyzed. Inverted repeat-like structure was found for at both ends of entMR10A and so that it suggested entMR10A of strain N1-33 could be formed from an insertion sequence. Attempting to eliminate the plasmid from strain N1-33 using the plasmid-curing agent novobiocin was obtained the mutant strain of N1-33 which seemed to overproduction of bacteriocin than the original strain, termed N41-51. The number of originated bacteriocin structural genes detected by real-time PCR showed that its level of the strain N41-51 was about twofold higher than that of N1-33, and correspondingly appeared to produce about twofold more bacteriocin compared with the original strain in these culture broth, respectively. This difference as a food preservative potential was examined whether it proves the same result in the actual food systems, by using steamed rice. The culture supernatant of strain N41-51 has confirmed to inhibit the growth of Bacillus cereus by significantly less amount added to steamed rice than that of N1-33. Practical Applications Besides having it with their usual meals, Japanese often eat steamed rice such as rice balls and in their lunch. The most important point we care at these cases is the food poisoning caused by Bacillus cereus, and thus, growth inhibition of B. cereus in steamed rice has been an important task for food industry. In this study, efficacy of the bacteriocin produced by Enterococcus faecalis N1-33 against B. cereus in steamed rice had shown. The difference in bacteriocin activity of the wild-type strain N1-33 and its mutant strain N41-51, which showed about twice as much bacteriocin production, was also reshown well in the actual food system. Also that, the high bacteriocin producing strain of N1-33, termed N41-51, could be obtained with a simple plasmid curing process.

Effect of the competitive growth of Lactobacillus sakei MN on the growth kinetics of Listeria monocytogenes Scott A in model meat gravy

Listeria monocytogenes is a foodborne pathogen capable of growth under refrigeration temperatures. The use of bacteriocin-producing lactic acid bacteria to inhibit Gram-positive pathogen growth may be an important tool to enhance the safety of refrigerated foods. The influence of three different populations of the bacteriocin-producing strain Lactobacillus sakei MN on the growth kinetic parameters of three different populations of L. monocytogenes Scott A co-cultured in model meat gravy at 4, 10, 16, and 22 °C was studied. The Baranyi growth model was used to estimate the kinetic parameters of L. monocytogenes and L. sakei for each strain cultured alone or in co-culture. The highest L. monocytogenes populations were achieved by pure cultures, decreasing in co-culture with the different inocula of L. sakei, at all temperatures. A modified logistic model was applied which includes a factor β that adjusts the effect of L. sakei on L. monocytogenes depending on the environmental conditions. The co-cultures of low (∼1log) L. monocytogenes inocula showed a decrease in β values when temperature increased, indicating that inter-species competition changes with temperature; the 2log- and 4log-inocula of L. monocytogenes co-cultures also showed this behavior but only with the higher initial population of L. sakei.

Isolation and preliminary characterisation of bacteriocin produced by Enterococcus faecium GHB21 isolated from Algerian paste of dates “ghars”

The bacteriocin-producing strain GHB21 isolated from the Algerian traditional paste of dates “ghars” was identified as Enterococcus faecium based on 16S rRNA sequence analysis. The bacteriocin produced by Enterococcus faecium GHB21 was sensitive to proteases, heat-stable, resistant to a wide range of pH and also to several chemicals. Recorded bacteriocin activity was higher when GHB21 was fermented in a bioreactor compared with static fermentation in a flask; it was also shown to be growth-associated and to display primary metabolite kinetics as its maximal production was detected in the early logarithmic growth phase. GHB21 presented a large activity spectrum towards different genera, and proved active against either Gram positive or Gram negative bacteria, including some pathogenic and/or spoilage bacteria. Partial purification of this bacteriocin by an adsorption-desorption method led to a fraction that lost its entire activity after 1 week of storage at 4 °C, or after 15 days when supplemented with bovine serum albumin; nevertheless the lyophilised fraction could remain stable with full activity even after 1 year. The partially purified bacteriocin exhibited a bactericidal effect on Listeria ivanovii subsp. ivanovii ATCC 19119 and could lead to its total inhibition after only 6 h but without concomitant cell lysis. Tricine-SDS-PAGE analysis of the partially purified bacteriocin indicated a low molecular weight of approximately 5 kDa.

Bacteriocin-producing strains of Lactobacillus plantarum inhibit adhesion of Staphylococcus aureus to extracellular matrix: quantitative insight and implications in antibacterial therapy

In the present study, the adhesion of bacteriocin-producing probiotic strains of Lactobacillus plantarum onto extracellular matrix (ECM) proteins such as collagen and mucin and their potential to prevent pathogen invasion onto the ECM was ascertained. Fluorescence-based in vitro assays indicated that L. plantarum strains CRA21, CRA38 and CRA52 displayed considerable adhesion to ECM molecules, which was comparable to the probiotic Lactobacillus rhamnosus GG. Flow cytometry-based quantitative assessment of the adhesion potential suggested that L. plantarum CRA21 exhibited superior adhesion onto the ECM as compared with other lactic acid bacteria strains. Furthermore, fluorescence-based assays suggested that the highest inhibition of Staphylococcus aureus adhesion onto collagen and mucin by bacteriocin-producing L. plantarum strains was observed in the exclusion mode as compared with the competition and displacement modes. This observation was supported by the higher binding affinity (k(d)) for the ECM exhibited by the L. plantarum strains as compared with S. aureus. Interestingly, a crude plantaricin A extract from food isolates of L. plantarum displayed potent antibacterial activity on ECM-adhered S. aureus cells. It is envisaged that the L. plantarum isolates displaying bacteriocinogenic and ECM-adhering traits can perhaps be explored to develop safe antibacterial therapeutic agents.

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.

Bacteriocinogenic potential of a probiotic strain Bacillus coagulans [BDU3] from Ngari

Bacteriocin producing strain BDU3 was isolated from a traditional fermented fish of Manipur Ngari. The strain BDU3 was identified as Bacillus coagulans by phenotypic and genotypic characterization. The BDU3 produced novel bacteriocin, which showed an antimicrobial spectrum toward a wide spectrum of food borne, and closely related pathogens with a MIC that ranged between 0.5 and 2.5μg/mL. The isolate was able to tolerate pH as low as 2.0 and up to 0.2% bile salt concentration. Three step purification was employed to increase the specific activity of the antimicrobial compound. The fractions were further chromatographed by Rp-HPLC C-18 column and the purified bacteriocin had a specific activity of ∼8500AU/mg. However, the potency of bacteriocin was susceptible to digestion with Proteinase K, Pepsin, SDS, EDTA and Urea. Molecular mass of purified bacteriocin was found to be 1.4kDa using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). The functional group was revealed by FTIR analysis. The cytotoxicity assay (MTT) using purified bacteriocin showed 2 times lower EC50 values compared to SDS. This is the smaller bacteriocin ever reported before from B. coagulans with greater antimicrobial potency with lower cytotoxicity. This bacteriocin raises the possibilities to be used as a biopreservative in food industries.