Purification and characterization of plantaricin Y,a novel bacteriocin produced by Lactobacillus plantarum 510

Lactobacillus plantarum 510, previously isolated from a koshu vineyard in Japan, was found to produce a bacteriocin-like inhibitory substance which was purified and characterized. Mass spectrometry analysis showed that the mass of this bacteriocin is 4,296.65 Da. A partial sequence, NH₂- SSSLLNTAWRKFG, was obtained by N-terminal amino acid sequence analysis. A BLAST search revealed that this is a unique sequence; this peptide is thus a novel bacteriocin produced by Lactobacillus plantarum 510 and was termed plantaricin Y. Plantaricin Y shows strong inhibitory activity against Listeria monocytogenes BCRC 14845, but no activity against other pathogens tested. Bacteriocin activity decreased slightly after autoclaving (121 °C for 15 min), but was completely inactivated by protease K. Furthermore, trypsin-digested bacteriocin product fragments retained activity against L. monocytogenes BCRC 14845 and exhibited a different inhibitory spectrum.     

<Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> isolated from cheese: production and partial characterization of bacteriocin B391

Lactobacillus plantarum B391, a strain isolated from an artisanal French cheese, is a producer of a bacteriocin, expressing activity against Enterococcus faecalis NCTC 775, Clostridium perfringens NCTC 13170 and several Listeria monocytogenes strains. High stability was recorded after heat treatment at 121 °C for 20 min and when stored at 4 °C for more than 40 days. A challenge test performed in milk for 11 days showed potential for the control of L. monocytogenes. In the presence of the lytic bacteriocin B391, L. monocytogenes cells present numerous morphology modifications of cell shape and surface structure as well as in the cell division pattern, resulting ultimately in lysis. The high level of Listeria growth inhibition obtained in the presence of Lb. plantarum B391, and the stability of B391 bacteriocin for a long period of time, make this strain potentially interesting to use in milk products to increase food safety.     

Fluorescence-Based Comparative Evaluation of Bactericidal Potency and Food Application Potential of Anti-listerial Bacteriocin Produced by Lactic Acid Bacteria Isolated from Indigenous Samples

The aim of the present study was to ascertain the potency of anti-listerial bacteriocin produced by lactic acid bacteria (LAB) isolated from indigenous samples of dahi, dried fish, and salt-fermented cucumber. A total of 231 LAB isolates were obtained from the samples, of which 51 isolates displayed anti-listerial activity. The anti-listerial LAB were identified by PCR as Lactobacillus sp., Pediococcus sp., Enterococcus sp., and Lactococcus sp. PCR also enabled the detection of Class IIa bacteriocin-encoding genes such as enterocin A, pediocin, and plantaricin A in some of the LAB isolates. The culture filtrate from anti-listerial LAB isolates demonstrated bacteriocin-like inhibitory substance (BLIS) against common Gram-positive pathogenic bacteria such as Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus, and partial characterization of BLIS confirmed the production of bacteriocin by the LAB isolates. Sensitive fluorescence-based assays employing specific probes indicated the comparative potencies of the bacteriocin and clearly revealed the membrane-targeted anti-listerial activity of the purified bacteriocin produced by selected LAB isolates. The food application potential of plantaricin A produced by a native isolate Lactobacillus plantarum CRA52 was evidenced as the bacteriocin suppressed the growth of Listeria monocytogenes Scott A inoculated in paneer samples that were stored at 8?°C for 5?days.     

Characterisation of the bacteriocins produced by two probiotic Lactobacillus isolates from idli batter

Lactobacillus plantarum JJ18 and Lactobacillus plantarum subsp. plantarum JJ60, probiotics from idli batter, produce bacteriocins JJ18 and JJ60 having a wide spectrum of activity. After optimising the environmental conditions for bacteriocin production the effect of various media components was determined. Maximum bacteriocin production was observed in MRS broth, pH 6.4 at 37 °C after 36 h. Tryptone (as nitrogen source) and glucose (as carbon source) are required for optimal production of bacteriocins JJ18 and JJ60. Activity was not affected by surfactants like Triton X-100, Tween 80 and Tween 20 or by treatment with NaCl, urea and EDTA. Protease treatment resulted in complete loss of activity of the partially purified bacteriocins JJ18 and JJ60, while lipase and α-amylase had no effect, indicating that the bacteriocin is a simple protein. Tris tricine SDS-PAGE electrophoresis depicted a single band of less than 3.5 kDa. However, the strain Lactobacillus plantarum JJ18 was inhibited by bacteriocin JJ60 and Lactobacillus plantarum JJ60 by bacteriocin JJ18, whereas no inhibition was observed against the respective producer strains, indicating that the two bacteriocins are different. The bacteriocins remained active over a wide range of pH and temperature. The bacteriocins were able to adsorb onto producer and target cells, Lactobacillus plantarum and Listeria monocytogenes and differentially in the presence of various surfactants, salts and solvents. A bactericidal mode of action was observed against Listeria monocytogenes. Given their wide spectrum of activity against various pathogens, the bacteriocins JJ18 and JJ60 can be applied as bio-preservatives in the food industry.     

Anti-listerial Bactericidal Activity of Lactobacillus plantarum DM5 Isolated from Fermented Beverage Marcha

The strain Lactobacillus plantarum DM5 was isolated from fermented beverage Marcha of Sikkim and explored for its antagonistic activity against food-borne pathogens. The cell-free supernatant of L. plantarum DM5 showed antibacterial activity of 6,400 AU/mL in MRS medium (pH 6.0) against the indicator strain Staphylococcus aureus. MRS medium supplemented with 15 g/L of maltose at 37 °C under static condition yielded highest antimicrobial activity (6,400 AU/mL) with 3 % increase in specific activity when compared to 20 g/L glucose. The antimicrobial compound was heat stable (60 min at 100 °C) and was active over a wide pH range. It showed bactericidal effect on S. aureus and Listeria monocytogenes by causing 96 and 98 % of cell lysis, respectively. The cell morphology of the treated S. aureus and L. monocytogenes was completely deformed as revealed by scanning electron microscopy, suggesting the high potential of L. plantarum DM5 as natural preservatives in food industry. The antimicrobial compound was purified by 80 % ammonium sulphate precipitation and showed antimicrobial activity of 12,800 AU/mL with 19-fold purification and a molecular mass of 15.2 kDa, indicating the proteinaceous nature of the compound.     

An in vitro study of Lactobacillus plantarum strains for the presence of plantaricin genes and their potential control of the table olive microbiota

Sixteen Lactobacillus plantarum strains, isolated from fermented table olives, were studied for the presence and expression of genes involved in the production of bacteriocins, pheromones and other peptides. The presence of 13 genes that belong to pln locus was monitored, while for the study of gene expression, producer strains were cultured in growth medium with variant salinity (0, 4, 6, and 8 % NaCl) and pH (3.5, 4.0, 4.5, and 6.4). The effect of producer strain on the growth of indicator microorganisms was evaluated using a well diffusion assay. In parallel, Real-Time PCR was employed to monitor the genetic expression of plnE/F and plnJ/K genes for strains that revealed the highest antimicrobial activity. The well diffusion assay showed that the growth of Lactobacillus pentosus was inhibited by six L. plantarum strains when cultured on control medium (0 % NaCl, pH 6.4). Moreover, when the same growth medium was supplemented with 4 and 6 % NaCl, the growth of L. pentosus was inhibited by three and two L. plantarum strains, respectively. Growth of L. pentosus was favoured when L. plantarum strains were cultured on a growth medium with lowered pH (3.5, 4.0, and 4.5). No inhibition of pathogens was observed, but in a few cases, inhibition of Aureobasidium pullulans was detected. The Real-Time PCR assay revealed that the expression of genes was dependent on producer strains and growth phase, whereas inhibition of indicator strains was enhanced in earlier stages of the growth curve in the presence of NaCl, although similar counts were obtained.     

Detoxification of enterotoxigenic Bacillus cereus (JX455159) isolated from meat by a local strain of Lactobacillus plantarum (JX282192)

Raw minced meat samples (25) were randomly collected from different slaughterhouses in Dakhlia and Sharkyia Governorates, Egypt. One hundred and fifty Bacillus species related to the cereus group were isolated from the collected meat samples using Mannitol Yolk Polymyxin (MYP) agar plates. Purified bacterial cultures were then tested for their virulence factors with respect to hemolysin, protease and lecithinase. Of the tested Bacillus strains (150), 81, 95.3 and 76 % of total tested Bacillus strains were positive for hemolysin, protease and lecithinase tests, respectively. The identity of one of the most potent strains suspected and encoded as Bacillus cereus F23 was confirmed by amplifying its 16S rRNA gene. The partial nucleotide sequence of the amplified 16S rRNA gene of the tested strain was submitted to GenBank with accession number JX455159. Multiplex PCR amplification of enterotoxin genes in the tested strain, using specific primers, yielded amplicons of molecular sizes 695 and 565 bp for enterotoxins hblC and cytK, respectively. Thermal resistance of B. cereus F23 (JX455159) spores was determined by calculating D values at 65, 75, 85 and 95 °C for 36, 25, 19 and 16 min, respectively, and the calculated Z value was recorded as 0.119 °C. A lactic acid bacteria (LAB) strain isolated from pickles was preliminary identified as Lactobacillus plantarum F14 (LBF14) and later confirmed by detecting its 16S rRNA gene, and it was submitted to GenBank with accession number JX282192. The identified LAB strain was tested as a bioprotective agent against toxigenic B. cereus F23 spores both in minced meat samples and BHI broth medium. A reduction in B. cereus F23 population between 4 and 6 log cycles under different tested conditions was recorded. The activity of virulence factors (protease and lecithinase) decreased and hemolytic activity was completely inhibited in the presence of 10³ CFU/ml of Lactobacillus plantarum F14 (JX282192). Inthe presence of 10⁵ CFU/ml Lactobacillus plantarum F14 (JX282192), protease and lecithinase activities of B. cereus F23 were decreased by 85 and 71 %, respectively.     

Encapsulation of Lactobacillus plantarum 423 and its Bacteriocin in Nanofibers

Plantaricin 423, produced by Lactobacillus plantarum 423, was encapsulated in nanofibers that were produced by the electrospinning of 18% (w/v) polyethylene oxide (200 000 Da). The average diameter of the nanofibers was 288 nm. Plantaricin 423 activity decreased from 51 200 AU/ml to 25 600 AU/ml and from 204 800 AU/ml to 51 200 AU/ml after electrospinning, as determined against Lactobacillus sakei DSM 20017 and Enterococcus faecium HKLHS, respectively. Cells of L. plantarum 423 encapsulated in nanofibers decreased from 2.3 × 10¹⁰ cfu/ml before electrospinning to 4.7 × 10⁸ cfu/ml thereafter. Cells entrapped in the nanofibers continued to produce plantaricin 423. This is the first report on the encapsulation of a bacteriocin and cells of L. plantarum in nanofibers. The method may be used to design a drug delivery system for bacteriocins and the encapsulation of probiotic lactic acid bacteria. The technology is currently being optimized.     

In vitro antifungal activity of lactic acid bacteria low molecular peptides against spoilage fungi of bakery products

Bio-preservation, a promising preservation method that involves the use of “friendly” microorganisms such as lactic acid bacteria, has recently become a topic of considerable interest. In the present study, 16 lactic acid bacteria isolates were evaluated for antifungal activity against six fungi commonly associated with bread spoilage. The antifungal compounds were heat stable at 121 °C, and only four isolates, DU15, IT10, TE10, and IS10, showed partial loss of activity when supernatants were treated with proteolytic enzymes. The four isolates showed high inhibition activity at pH 3 and were identified using 16S rDNA sequencing as belonging to Leuconostoc mesenteroides DU15, Lactobacillus plantarum TE10, Lactobacillus plantarum IT10, and Lactobacillus plantarum IS10. The minimum germination inhibitions were 30 mg, 50 mg, 40 mg, and 50 mg for TE10, IT10, DU15, and IS10 respectively. The optimum conditions for the strains to produce antifungal compounds were 37 °C for 48 h for IT10, IS10, and TE10, and 30 °C for 24 h for DU15. Antifungal activity was increased threefold when supernatants were filtered using 10 KDa membranes. These findings demonstrate the potential of using lactic acid bacteria antifungal peptides as natural preservatives in bakery products to control the growth of spoilage fungi.     

Characterization of a new organization of the plantaricin locus in the inducible bacteriocin-producing<Emphasis Type="Italic"> Lactobacillus plantarum</Emphasis> J23 of grape must origin

Lactobacillus plantarum J23 was previously characterized as a bacteriocin-producer-strain when it was cocultured with other lactic acid bacteria. In this work, the genetic organization of the pln locus in the J23 strain was studied and compared with those of previously described L. plantarum C11, WCFS1 and NC8 strains. A new organization of the plantaricin locus was detected in the J23 strain. The sequenced fragment (20,266 bp) comprised plnJLR, plnMNOP, plnEFI, plnGHSTUVWXY, and plNC8IF-plNC8HK-plnD operons, as well as a new region that includes three new orfs (GenBank accession number DQ323671). When the J23 pln gene sequences were compared with those included in the GenBank database, the identity of the putative encoded proteins was in the range 67.1–100%. The regulatory system and the repertoire of putative bacteriocins of the J23 pln locus presented important differences with respect to the ones of C11, WCFS1 and NC8, such as the absence of plnK and the presence of a larger plnJ gene than the previously described for the other L. plantarum strains. The pln locus in L. plantarum strains seems to be a mosaic-like structure with different modules and reorganizations that presents highly conserved regions related to transport and bacteriocin maturation and variable regions related to regulation and bacteriocin production.     

Viability and Stress Response of Putative Probiotic <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> Strains in Honey Environment

Due to problem of preservation of dairy products which serve as a matrix for probiotics, it is challenging to use these probiotics as food supplements in many developing countries. To determine the suitability of the Lactobacillus strains for exploitation as probiotics in honey, we investigated the effect of their storage on the viability, functionality, and the mechanism associated with their protective effect. Three isolates obtained from our laboratory collection were identified through amplification of the 16S rRNA gene. The viability of the strains in honey at different storage conditions was studied. Three genes (hdc, gtf, and clpL) responsible for the resistance of bacteria in acidic environments were screened. SDS-PAGE analysis of total protein was performed to observe protein profile changes of the strains after exposure to honey. All the three isolates, namely, GGU, GLA51, and GLP56, were identified as Lactobacillus plantarum strains. After 28 days of storage in honey at 4 °C, viable cell concentrations of the three strains were higher than 2.04?×?10⁶ CFU/ml. During the same period at room temperature, only the Lactobacillus plantarum GLP56 strain remained viable with a cell concentration of 1.86?×?10⁴ CFU/ml. The clpL gene coding for ATPase was detected in all the three strains. The protein of molecular weight ~?50 kDa was absent in the protein profile of Lactobacillus plantarum GGU after 60 days of storage in honey at 4 °C. The Lactobacillus plantarum GLP56, Lactobacillus plantarum GLA51, and Lactobacillus plantarum GGU strains exposed to honey can withstand acidic environmental stress but their viability declines over time.     

Lactobacillus pentosus B231 Isolated from a Portuguese PDO Cheese: Production and Partial Characterization of Its Bacteriocin

Bacteriocin B231 produced by Lactobacillus pentosus, isolated from an artisanal raw cow’s milk protected designation of origin Portuguese cheese, is a small protein with an apparent relative mass of about 5 kDa and active against a large number of Listeria monocytogenes wild-type strains, Listeria ivanovii and Listeria innocua. Bacteriocin B231 production is highly dependent on the type of the culture media used for growth of Lact. pentosus B231. Replacement of glucose with maltose yielded the highest bacteriocin production from eight different carbon sources. Similar results were recorded in the presence of combination of glucose and maltose or galactose. Production of bacteriocin B231 reached maximal levels of 800 AU/ml during the stationary phase of growth of Lact. pentosus B231 in MRS broth at 30 °C. Bacteriocin B231 (in cell-free supernatant) was sensitive to treatment with trypsin and proteinase K, but not affected by the thermal treatment in range of 55–121 °C, or freezing (?20 °C). Bacteriocin production and inhibitory spectrum were evaluated. Gene encoding plantaricin S has been detected in the genomic DNA. Virulence potential and safety of Lact. pentosus B231 were assessed by PCR targeted the genes gelE, hyl, asa1, esp, cylA, efaA, ace, vanA, vanB, hdc1, hdc2, tdc and odc. The Lact. pentosus B231 strains harbored plantaricin S gene, while the occurrence of virulence, antibiotic resistance and biogenic amine genes was limited to cytolysin, hyaluronidase, aggregation substance, adhesion of collagen protein, gelatinase, tyrosine decarboxylase and vancomycin B genes.     

Purification and Characterization of Bacteriocin Produced by Lactobacillus brevis UN Isolated from Dhulliachar: a Traditional Food Product of North East India

A bacteriocin producing strain Lactobacillus brevis UN isolated from Dulliachar—a salted pickle and identified by biochemical and molecular methods. L. brevis UN was found to produce bacteriocin with broad spectrum activity against spoilage causing/food borne pathogens viz. L. monocytogenes, C. perfringens, S. aureus, L. mesenteroides, L. plantarum and B. cereus. Bacteriocin production was optimized through classical one variable at a time method. The isolate showed maximum bacteriocin production at early stationary phase, pH 4.0, temperature 35 °C and with an inoculum size of 1.5 OD @ 10 %. Bacteriocin produced by L. brevis UN was purified to homogeneity by single step gel exclusion chromatography and was most active at pH 6.0 and 7.0, stable up to 100 °C and was proteinaceous in nature. The results of NMR revealed the presence of proline, glutamic acid, aspartic acid, leucine, isoleucine and serine in its peptide structure. PCR amplification analysis determined that bacteriocin encoded gene in L. brevis UN was plasmid bound.     

Inhibition of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> in Hot Dogs by Surface Application of Freeze-Dried Bacteriocin-Containing Powders from Lactic Acid Bacteria

Six lactic acid bacteria (LAB) strains, Lactococcus lactis BFE 920, L. lactis subsp. lactis ATCC 11454, L. lactis subsp. cremoris ATCC 14365, Lactobacillus curvatus L442, Lact. curvatus LTH 1174, and Lact. bavaricus MN, were grown in cheddar cheese whey supplemented with complex nutrient sources. Cell-free culture supernatants were freeze-dried, and the resulting bacteriocin-containing powders were applied on the surface of hot dogs that were inoculated (~4 log cfu/hot dog) with a five-strain Listeria monocytogenes cocktail. Hot dogs were vacuum-sealed and stored at 4 °C for 4 weeks. L. monocytogenes was enumerated, using both tryptic soy agar (TSA) and oxford listeria agar (OXA), on day 0 and at 1, 2, 3, and 4 weeks of the refrigerated storage. In hot dogs containing only the L. monocytogenes inoculum, L. monocytogenes counts increased from 4 up to 7 log cfu/hot dog. All samples containing freeze-dried bacteriocin-containing powders exhibited significantly lowered (P < 0.05) L. monocytogenes populations on the surface of hot dogs throughout the 4-week study except for bavaricin MN powder. Bacterial counts on hot dogs packed without any powder were statistically equal on day 0 when enumerated on OXA. Freeze-dried bacteriocin-containing powders from Lact. curvatus L442 and L. lactis subsp. cremoris ATCC 14365 decreased L. monocytogenes populations on the surface of hot dogs by greater than 2 log cfu/hot dog throughout the 4-week study. For the powdered bacteriocin preparations from L. lactis BFE 920, L. lactis subsp. lactis ATCC 11454, and Lact. curvatus LTH 1174, L. monocytogenes populations were determined to be approximately 3-log cfu/hot dog after 4 weeks of storage.     

Production of a Class IIb Bacteriocin with Broad-spectrum Antimicrobial Activity in Lactiplantibacillus plantarum RUB1

Bacteriocins produced by lactic acid bacteria have potential use as natural food preservatives, which may alleviate current problems associated with the overuse of antibiotics and emerging multi-drug-resistant microbes. In this work, Lactiplantibacillus plantarum RUB1 was found to produce a class IIb bacteriocin with strong antibacterial activity. Except for plnXY encoding putative proteins, L. plantarum RUB1 contains most genes in five operons (plnABCD, plnGHSTUVW, plnMNOP, plnIEF, and plnRLJK) related to bacteriocin synthesis. Adding low (100 and 500 ng/mL) and medium (1 μg/mL) concentrations of PlnA to broth promoted bacteriocin production and upregulated bacteriocin gene plnA, while high concentrations (50 and 200 μg/mL) inhibited expression of these genes. Co-culturing L. plantarum RUB1 with Enterococcus hirae 1003, Enterococcus hirae LWS, Limosilactobacillus fermentum RC4, L. plantarum B6, and even Listeria monocytogenes ATCC 19111 and Staphylococcus aureus ATCC 6538 enhanced bacteriocin activity and expression of bacteriocin-related genes. This study verifies that PlnA can indeed upregulate the expression of bacteriocin genes, and also bacteriocin production can be induced by co-culture with some specific bacteria or their cell-free supernatants. Bacteriocin production by L. plantarum RUB1 is mediated by a quorum sensing mechanism, directly influenced by autoinducing peptide or specific strains. The findings provide new methods and insight into bacteriocin production mechanisms.

     

Lactobacillus plantarum 24, Isolated From the Marula Fruit (Sclerocarya birrea), has Probiotic Properties and Harbors Genes Encoding the Production of Three Bacteriocins

Lactobacillus plantarum 24, isolated from marula fruit grows at pH 4.0 and tolerates acid levels and bile concentrations normally present in the human gastro-intestinal tract. Wistar rats that have been administered L. plantarum 24 showed no signs of discomfort or abnormal behavior. Tissue samples from the liver, spleen and intestine appeared normal. Furthermore, strain 24 harbors the genes encoding plantaricins A, F, and NC8α, a gene encoding immunity to plantaricin, and an ABC transporter similar in sequence to that reported for plantaricin G. At least one antimicrobial peptide within the size range of plantaricins A, F, and NC8α has been detected on a tricine-SDS–PAGE gel. Little is known about the microbial population in marula. This is the first report of a L. plantarum strain from marula fruit with bacteriocin genes and probiotic properties.     

Nisin Z produced by <Emphasis Type="Italic">Lactococcus lactis</Emphasis> from bullfrog hatchery is active against <Emphasis Type="Italic">Citrobacter freundii</Emphasis>, a red-leg syndrome related pathogen

Lactococcus lactis subsp. lactis CRL 1584 isolated from a bullfrog hatchery produces a bacteriocin that inhibits both indigenous Citrobacter freundii (a Red-Leg Syndrome related pathogen) and Lactobacillus plantarum, and Listeria monocytogenes as well. Considering that probiotics requires high cell densities and/or bacteriocin concentrations, the effect of the temperature on L. lactis growth and bacteriocin production was evaluated to find the optimal conditions. Thus, the growth rate was maximal at 36 °C, whereas the highest biomass and bacteriocin activity was achieved between 20 and 30 °C and 20–25 °C, respectively. The bacteriocin synthesis was closely growth associated reaching the maximal values at the end of the exponential phase. Since bacteriocins co-production has been evidenced in bacterial genera, a purification of the bacteriocin/s from L. lactis culture supernatants was carried out. The active fraction was purified by cationic-exchange chromatography and then, a RP-HPLC was carried out. The purified sample was a peptide with a 3353.05 Da, a molecular mass that matches nisin Z, which turned out to be the only bacteriocin produced by L. lactis CRL 1584. Nisin Z showed bactericidal effect on C. freundii and L. monocytogenes, which increased in the presence l-lactic acid?+?H₂O₂. This is the first report on nisin Z production by L. lactis from a bullfrog hatchery that resulted active on a Gram-negative pathogen. This peptide has potential probiotic for raniculture and as food biopreservative for bullfrog meat.     

Suppression of Listeria monocytogenes Scott A in Fluid Milk by Free and Liposome-Entrapped Nisin

Nisin is an antimicrobial polypeptide inhibitory toward Gram-positive bacterial pathogens, including Listeria monocytogenes. Encapsulating nisin in lipid nanocapsules (i.e., liposomes) has been shown to protect antimicrobial functionality in complex food matrices. The capacity of liposomes to encapsulate a fluorescent reporter was determined via spectroscopy. Survival and growth of L. monocytogenes incubated in fluid milk containing 50 IU/ml free or liposome-entrapped nisin was assayed via periodic enumeration of survivors. Liposomes were formulated from phosphatidylcholine (PC) and phosphatidyl-DL-glycerol (PG) and prepared as PC, PC/PG 7/3 or PC/PG 6/4 (mol. fraction). Antilisterial activity of nisin-loaded liposomes was determined in ultra-high temperature processed fluid milk containing approximately 4.0 log₁₀ CFU/ml L. monocytogenes Scott A plus liposomal or free nisin at 50 IU/mL. Samples were aerobically held at 5 or 20°C; L. monocytogenes were enumerated via plating after 0, 1, 3, 6, 12, 24, 48, and 72 incubation hours. Liposome entrapment did not enhance pathogen inhibition when compared to free nisin as a function of storage temperature or incubation duration.     

Bacteriocins ofLactobacillus plantarum strains from fermented foods

Bacteriocin-producing strains may be used as protective cultures to improve the microbial safety of foods. The crude or purified form of these antimicrobial agents may also be applied directly as food preservative. This review gives survey of the different bacteriocins produced byLactobacillus plantarum isolated from fermented food products with particular emphasis on their genetic and biochemical properties. A number of bacteriocins are produced byL. plantarum. These include plantaricin B, plantaricin BN, plantaricin A, plantaricin C, plantaricin S and T, plantaricin, F, plantaricin C19 and SA6 and other unnamed bacteriocins. However, with the exception of plantaricin A, information on the genetic and biochemical characteristics ofL. plantarum bacteriocins is still scant.