Investigation into the Potential of Bacteriocinogenic Lactobacillus plantarum BFE 5092 for Biopreservation of Raw Turkey Meat

The bacteriocin-producing Lactobacillus plantarum BFE 5092 was assessed for its potential as a protective culture in the biopreservation of aerobically stored turkey meat. This strain produces three bacteriocins, i.e. plantaricins EF, JK and N. The absolute expression of Lactobacillus plantarum BFE 5092 16S rRNA housekeeping gene, as well as l-ldh, plnEF and plnG genes as determined by quantitative, real-time-PCR, revealed that these genes were expressed to similar levels when the strain was grown at 8 and 30 °C in MRS broth. On turkey meat, Lactobacillus plantarum BFE 5092 did not grow but survived, as indicated by similar viable cell numbers during a 9-day storage period at 8 °C. When inoculated at 1 × 10⁷ CFU/g on the turkey meat and subsequently stored at 10 °C, the culture did again not show good growth. Lactobacillus plantarum BFE 5092 could not inhibit the growth of naturally occurring listeriae or Gram-negative bacteria on the turkey meat at 10 °C, or that of Listeria monocytogenes when it was co-inoculated at a level of 1 × 10⁵ CFU/g. Gene expression analyses showed that the bacteriocin genes were expressed on turkey meat stored at 10 °C. Moreover, the investigation into the absolute expression of the three plantaricin genes of Lactobacillus plantarum BFE 5092 in co-culture with Listeria monocytogenes on turkey meat by qRT-PCR showed that the plantaricin genes were indeed expressed during the low-temperature storage condition. The Lactobacillus plantarum BFE 5092 strain overall could not effectively inhibit L. monocytogenes and therefore it would not make a suitable protective culture for biopreservation of turkey meat stored aerobically at low temperature.     

Selection and evaluation of functional characteristics of autochthonous lactic acid bacteria isolated from traditional fermented stinky bean (<Emphasis Type="Italic">Sataw-Dong</Emphasis>)

The aim of this study was to evaluate the technological and functional potential of lactic acid bacteria (LAB) isolated from fermented stinky bean (Sataw-Dong). Of the 114 LAB colonies isolated from spontaneously fermented stinky bean which showed inhibitory activity against two food-borne pathogens (Staphylococcus aureus DMST 4480 and Escherichia coli DMST 4212), the five isolates (KJ03, KJ15, KJ17, KJ22, KJ23) exhibiting excellent antagonistic activity were subjected to further study. These five strains showed titratable acidity as lactic acid in the range of 1.47–1.55 %, with strains KJ03 and KJ23 additionally exhibiting a high NaCl tolerance of >7 % (w/v). Using 16S rRNA gene sequence analysis, strains KJ03 and KJ23 were identified as Lactobacillus plantarum and L. fermentum, respectively, and further investigated for their functional properties in vitro. Both strains survived well in a simulated gastrointestinal tract environment with <1 log cell decrease over 8 h (>8 log CFU/ml). Lactobacillus plantarum KJ03 showed the best performance with respect to cholesterol removal (53 %), while L. fermentum KJ23 showed the highest cell-surface hydrophobicity (39.5 %). Neither of the two strains showed any hemolysis activity. Both strains hydrolyzed glycodeoxycholic and taurodeoxycholic acids. In terms of antibiotic susceptibility, L. fermentum KJ23 was not sensitive to tetracycline. Taking all of the results into account, L. plantarum KJ03 possessed desirable in vitro functional properties. This strain is therefore a good candidate for further investigation for use in Sataw-Dong fermentation to assess its technological performance as a potential probiotic starter.     

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.     

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.     

Bacterial community compositions of tomato (Lycopersicum esculentum Mill.) seeds and plant growth promoting activity of ACC deaminase producing Bacillus subtilis (HYT-12-1) on tomato seedlings

Study of endophytic bacteria within plant seeds is very essential and meaningful on account of their heritability and versatility. This study investigated Bacillus bacterial communities within the seeds of four commercial tomato varieties, by 16S rRNA gene PCR-RFLP (restriction fragment length polymorphism). Phylogenetic analysis of 16S rRNA gene sequences indicated that the 22 representative isolates belonged to five species of genus Bacillus and the bacterial compositions showed remarkable differences among tomato varieties. Isolates exhibited multiple plant growth promoting (PGP) traits: 37 % of indole-3-acetic acid production; 37 % of phosphate solubilization; 24 % of siderophores production; 85 % of potential nitrogen fixation and 6 % of 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Isolate HYT-12-1 was shown to have highest ACC deaminase activity (112.02 nmol α-ketobutyrate mg^?1 protein h^?1) among the five ACC deamiase producing strains. 16S rRNA gene sequencing indicated that the isolate HYT-12-1 shared the highest sequence similarity (100 %) with B. subtilis. PGP experiments under gnotobiotic and greenhouse conditions revealed the ability of strain HYT-12-1 to enhance the growth of tomato seedlings. This is the first study to describe endophytic Bacillus communities within tomato seeds, and the results suggest that B. subtilis strain HYT-12-1 would have a great potential for industrial application as biofertilizer in the future.     

In vitro antifungal,probiotic and antioxidant properties of novel Lactobacillus plantarum K46 isolated from fermented sesame leaf

This study aimed to describe the diversity of antifungal lactic acid bacteria (LAB) in popular traditional Korean fermented food. A total of 22 LAB strains was selected and subjected to a monophasic identical approach using 16S rRNA gene sequence analysis. Antifungal LAB associated with fermented food was identified as Lactobacillus plantarum (9), Lactobacillus graminis (5), Lactobacillus pentosus (4), Lactobacillus sakei (2), Lactobacillus paraplantarum (1), and Leuconostoc mesenteroides subsp. mesenteroides (1). Novel Lactobacillus plantarum strain K46 exhibited comparatively better antifungal activity against several spoilage fungi, and was deposited in the Korean Collection for Type Cultures (KACC91758P). Antifungal substances from the spent medium in which K46 was cultivated were extracted with ethyl acetate. Antifungal activity was assessed using the broth micro dilution technique. Compounds were characterized based on infrared, ¹³C nuclear magnetic resonance (NMR), and ¹H NMR spectral data. The minimum inhibitory concentration (MIC) of the compounds against Aspergillus clavatus, Aspergillus oryzae, Penicillium chrysogenum and Penicillium roqueforti was 2.5 mg/mL and that against Aspergillus fumigatus, Aspergillus niger, Curvularia lunata and Gibberella moniliformis was 5.0 mg/mL. K46 was able to survive gastrointestinal conditions simulating the stomach and the duodenum passage with the highest percentage of hydrophobicity. In addition, its resistance to hydrogen peroxide and highest hydroxyl radical and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities, with inhibition rates of 43.53 % and 56.88 %, respectively, were to its advantage. An antimicrobial susceptibility pattern was an intrinsic feature of this strain, thus consumption does not represent a health risk to humans. The results showed the potential of K46 strain as an antifungal, probiotic and antioxidant culture, and hence it was determined to be suitable for application in functional foods.     

Genotyping and Toxigenic Potential of Bacillus subtilis and Bacillus pumilus Strains Occurring in Industrial and Artisanal Cured Sausages

Artisanal and industrial sausages were analyzed for their aerobic, heat-resistant microflora to assess whether new emerging pathogens could be present among Bacillus strains naturally contaminating cured meat products. Sixty-four isolates were characterized by randomly amplified polymorphic DNA (RAPD)-PCR and fluorescent amplified fragment length polymorphism (fAFLP). The biotypes, identified by partial 16S rRNA gene sequence analysis, belonged to Bacillus subtilis, Bacillus pumilus, and Bacillus amyloliquefaciens species. Both RAPD-PCR and fAFLP analyses demonstrated that a high genetic heterogeneity is present in the B. subtilis group even in strains harvested from the same source, making it possible to isolate 56 different biotypes. Moreover, fAFLP analysis made it possible to distinguish B. subtilis from B. pumilus strains. The strains were characterized for their toxigenic potential by molecular, physiological, and immunological techniques. Specific PCR analyses revealed the absence of DNA sequences related to HBL, BcET, NHE, and entFM Bacillus cereus enterotoxins and the enzymes sphingomyelinase Sph and phospholipase PI-PLC in all strains; also, the immunological analyses showed that Bacillus strains did not react with NHE- and HBL-specific antibodies. However, some isolates were found to be positive for hemolytic and lecithinase activity. The absence of toxigenic potential in Bacillus strains from the sausages analyzed indicates that these products can be considered safe under the processing conditions they were produced; however, great care should be taken when the ripening time is shortened, particularly in the case of traditional sausages, which could contain high amounts of Bacillus strains and possibly some B. cereus cells.     

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.     

Enhancement of alkaline protease production in Bacillus circulans using plasmid transformation

Plasmid transformation is an efficient and crucial biotechnological tool that enables the enhancement of many important microbial characters that would be beneficial in a lot of industrial, agricultural and environmental applications. In the present study, five Bacillus species (B. subtilis, B. cereus, B. alvei, B. circulans and B. pumilus) were investigated. They were isolated from agricultural soils of different local arid environments of the Kingdom of Saudi Arabia, identified and characterized for their plasmid content. The main objective of the present study was to enhance the production of alkaline protease in Bacillus circulans (the recipient strain) through plasmid transformation from B. subtilis (the donor strain). All the tested Bacillus strains successfully produced unique multiple (3, 4 and 5) spontaneous antibiotic resistant mutants against chloramphenicol, neomycin, rifampicin, streptomycin, kanamycin and tetracycline and all of which were mutated to Rif_r strains. B. pumilus showed the highest resistance against five of the six tested antibiotics while both of B. alvei and B. circulans showed the lowest resistance to only three of the tested antibiotics. Results revealed that B. subtilis was the best among the tested species concerning the production of alkaline protease (90.2 U/ml) while B. pumilus was the lowest in activity (40.3 U/ml). Screening of plasmid content revealed the presence of one or two mega indigenous plasmids in all the tested species. The four transformant strains BC ₁ , BC ₂ , BC ₃ and BC ₄ resulting from plasmid transformation exhibited significant increases in the activity of alkaline protease and recorded 2.31- to 3-fold increases compared to the parent B. circulans cells and 2.11- to 2.75-fold increases compared to the donor cells of B. subtilis. They also acquired antibiotic resistance to tetracycline and chloramphenicol that was completely absent in the parent cells of B. circulans. Results revealed that plasmid transformation among the tested Bacillus spp. is a powerful technique that can be efficiently exploited to enhance alkaline protease production in the transformed Bacillus spp. compared to their wild strains and we recommend using the improved transformant strains for commercial and industrial purposes.     

Genomic Analysis and Comparative Hexavalent Chromium Reduction Potential of Predominant Bacillus species Isolated from Chromite Mine Soil

Ten predominant bacteria (CSB 1-10), isolated from chromite mine soil of Sukinda, Odisha, were characterized by means of biochemical and 16S rRNA gene sequencing. All of the bacterial isolates were Gram-positive, spore-forming, and motile rods with diameter ranging from 1.57–2.79 μm and identified as Bacillus species. Based on 16S rRNA gene sequencing and phylogenetic tree construction, 10 Bacillus species were grouped into two clusters: Bacillus subtilis cluster with four species (two of B. amyloliquefaciens, and one each of B. tequilensis and B. mojavensis); and Bacillus cereus cluster containing six species of B. cereus. Secondary rRNA structure predicted for all 10 bacteria using 16S rRNA sequences revealed some degree of genetic variations among the species. Among the isolated bacteria, CSB-9 was found to be the most efficient chromate reducing strain (0.8 × 10^?4 mg mg^?1 h^?1) in comparison to the others. Chromate reduction of the bacteria was associated with the contribution of extracellular enzyme production, and highest enzyme activity (0.9 ± 0.09 U mL^?1) was observed in CSB-9 (B. amyloliquefaciens). The present study revealed the dominance of Bacillus species in the chromite mine soil and their potential for bioremediation of hexavalent chromium from the polluted environments.     

Isolation, Characterization and Identification of a Potential Probiont from South Indian Fermented Foods (Kallappam, Koozh and Mor Kuzhambu) and Its Use as Biopreservative

Twenty-five strains of lactic acid bacteria (LAB) isolated from South Indian traditional fermented foods Kallappam batter, Koozh and Mor Kuzhambu. Further 6 strains were selected based on their antimicrobial activity. They were identified according to morphological, biochemical and physiological criteria. Identification by 16S rDNA sequence homology of the isolates revealed the presence of Weissella paramesenteroides, Lactobacillus plantarum and Lactobacillus fermentum. Lactobacillus plantarum AS1 showed maximum antimicrobial activity among 6 strains and this strain was chosen for biopreservation. When male Albino Wistar rats were fed with L. plantarum AS1 (approx. 10⁹ cells/mL for a month), there was no sign of any illness and they were on par with control rats in terms of weight gain/week. In the L. plantarum AS1–treated group, there was reduction in the populations of indigenous microflora of coliforms, yeast and molds; however, the lactobacilli population increased comparatively. L. plantarum AS1 was able to retain its normal growth in the presence of increasing concentration of bile salt in the MRS and it also tolerated the artificial gastric juice simulating the condition inside the stomach where it was viable for 24 h with bacterial count of 6.079 logCFU/mL. L. plantarum AS1 reduced the cholesterol in the MRS broth by 57.3%. Hence, all these properties established it as an effective probiont. L. plantarum AS1 found to be an effective biopreservative in cheese, where it decreased the population of Salmonella typhi by 2.95 log cycles.     

Potential probiotic properties of phytase-producing Lactobacillus salivarius FC113

Probiotics have known efficacy as dietary supplements. Here, Lactobacillus strain F113 was characterized for probiotic use. Strain FC113 was selected as having the highest phytase activity (403.6 U) among tested strains showing acid tolerance and nitrite production. FC113 was tentatively identified as Lactobacillus salivarius based on an API 50 CHL assay and 16S rRNA gene analysis. The production of interleukin (IL)-1α and tumor necrosis factor (TNF)-α was measured in in vitro culture experiments. Cytokine production by L. salivarius FC113 at 1?×?10⁷ CFU/ml was approximately 175.5?±?36.40 pg/mL IL-1α and 353.5?±?61.79 pg/mL TNF-α. L. salivarius FC113 was profoundly resistant to artificial gastric juice (pH 2.5, 1 % pepsin), and persisted for 24 h in artificial bile acid. According to results obtained with an API ZYM kit, L. salivarius FC113 did not generate carcinogenic enzymes. L. salivarius F113 had an inhibitory effect on food-borne pathogens, and adhered strongly to HT-29 human intestinal epithelial cell lines. These results show that L. salivarius FC113 has probiotic characteristics, and exhibits high feed bioavailability in the host animal, in addition to an immune-stimulating effect.     

Isolation and identification of a new intracellular antimicrobial peptide produced by Paenibacillus alvei AN5

A wild-type, Gram-positive, rod-shaped, endospore-forming and motile bacteria has been isolated from palm oil mill sludge in Malaysia. Molecular identification using 16S rRNA gene sequence analysis indicated that the bacteria belonged to genus Paenibacillus. With 97 % similarity to P. alvei (AUG6), the isolate was designated as P. alvei AN5. An antimicrobial compound was extracted from P. alvei AN5-pelleted cells using 95 % methanol and was then lyophilized. Precipitates were re-suspended in phosphate buffered saline (PBS), producing an antimicrobial crude extract (ACE). The ACE showed antimicrobial activity against Salmonella enteritidis ATCC 13076, Escherichia coli ATCC 29522, Bacillus cereus ATCC 14579 and Lactobacillus plantarum ATCC 8014. By using SP-Sepharose cation exchange chromatography, Sephadex G-25 gel filtration and Tricine SDS-PAGE, the ACE was purified, which produced a ~2-kDa active band. SDS-PAGE and infrared (IR) spectroscopy indicated the proteinaceous nature of the antimicrobial compound in the ACE, and liquid chromatography electrospray ionization mass spectroscopy and de novo sequencing using an automatic, Q-TOF premier system detected a peptide with the amino acid sequence F–C–K–S–L–P–L–P–L–S–V–K (1,330.7789 Da). This novel peptide was designated as AN5-2. The antimicrobial peptide exhibited stability from pH 3 to 12 and maintained its activity after being heated to 90 °C. It also remained active after incubation with denaturants (urea, SDS and EDTA).     

Rope-Producing Strains of Bacillus spp. from Wheat Bread and Strategy for Their Control by Lactic Acid Bacteria

Two types of white wheat bread (high- and low-type loaves) were investigated for rope spoilage. Thirty of the 56 breads tested developed rope spoilage within 5 days; the high-type loaves were affected by rope spoilage more than the low-type loaves. Sixty-one Bacillus strains were isolated from ropy breads and were characterized on the basis of their phenotypic and genotypic traits. All of the isolates were identified as Bacillus subtilis by biochemical tests, but molecular assays (randomly amplified polymorphic DNA PCR assay, denaturing gradient gel electrophoresis analysis, and sequencing of the V3 region of 16S ribosomal DNA) revealed greater Bacillus species variety in ropy breads. In fact, besides strains of B. subtilis, Bacillus licheniformis, Bacillus cereus, and isolates of Bacillus clausii and Bacillus firmus were also identified. All of the ropy Bacillus isolates exhibited amylase activity, whereas only 32.4% of these isolates were able to produce ropiness in bread slices after treatment at 96°C for 10 min. Strains of lactic acid bacteria previously isolated from sourdough were first selected for antirope activity on bread slices and then used as starters for bread-making experiments. Prevention of growth of approximately 10⁴ rope-producing B. subtilis G1 spores per cm² on bread slices for more than 15 days was observed when heat-treated cultures of Lactobacillus plantarum E5 and Leuconostoc mesenteroides A27 were added. Growth of B. subtilis G1 occurred after 7 days in breads started with Saccharomyces cerevisiae T22, L. plantarum E5, and L. mesenteroides A27.     

Bacillus mesophilum sp. nov., strain IITR-54T,a novel 4-chlorobiphenyl dechlorinating bacterium

The taxonomic position of a Gram-positive, endospore-forming bacterium isolated from soil sample collected from an industrial site was analyzed by a polyphasic approach. The strain designated as IITR-54^T matched most of the phenotypic and chemical characteristics of the genus Bacillus and represents a novel species. It was found to biodegrade 4-chlorobiphenyl through dechlorination and was isolated through enrichment procedure from an aged polychlorinated biphenyl-contaminated soil. Both resting cell assay and growth under aerobic liquid conditions using 4-chlorobiphenyl as sole source of carbon along with 0.01 % yeast extract, formation of chloride ions was measured. 16S rRNA (1,489 bases) nucleotide sequence of isolated strain was compared with those of closely related Bacillus type strains and confirmed that the strain belongs to the genus Bacillus. Strain IITR-54^T differs from all other species of Bacillus by at least 2.1 % at the 16S rRNA level, and the moderately related species are Bacillus oceanisediminis (97.9 %) followed by Bacillus infantis (97.7 %), Bacillus firmus (97.4 %), Bacillus drentensis (97.3 %), Bacillus circulans (97.2 %), Bacillus soli (97.1 %), Bacillus horneckiae (97.1 %), Bacillus pocheonensis (97.1 %) and Bacillus bataviensis (97.1 %), respectively. The cell wall peptidoglycan contained meso-diaminopimelic acid and the major isoprenoid quinone was MK-7. Major fatty acids are iso-C_15:0 (32.4 %) and anteiso-C_15:0 (27.4 %). Predominant polar lipids are diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The results of physiological and biochemical tests allowed the genotypic and phenotypic distinctiveness of strain IITR-54^T with its phylogenetic relatives and suggest that the strain IITR-54^T should be recognized as a novel species, for which the name Bacillus mesophilum sp. nov. is proposed. The type strain is IITR-54^T (= MTCC 11060^T = JCM 19208^T).     

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.     

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.     

<Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> as a Probiotic Potential from Kouzeh Cheese (Traditional Iranian Cheese) and Its Antimicrobial Activity

The aim of this study is to isolate and identify Lactobacillus plantarum isolates from traditional cheese, Kouzeh, and evaluate their antimicrobial activity against some food pathogens. In total, 56 lactic acid bacteria were isolated by morphological and biochemical methods, 12 of which were identified as Lactobacillus plantarum by biochemical method and 11 were confirmed by molecular method. For analyzing the antimicrobial activity of these isolates properly, diffusion method was performed. The isolates were identified by 318 bp band dedicated for L. plantarum. The isolated L. plantarum represented an inhibitory activity against four of the pathogenic bacteria and showed different inhibition halos against each other. The larger halos were observed against Staphylococcus aureus and Staphylococcus epidermidis (15 ± 0.3 and 14.8 ± 0.7 mm, respectively). The inhibition halo of Escherichia coli was smaller than that of other pathogen and some L. plantarum did not show any inhibitory activity against E. coli, which were resistant to antimicrobial compounds produced by L. plantarum. The isolated L. plantarum isolates with the antimicrobial activity in this study had strong probiotic properties. These results indicated the nutritional value of Kouzeh cheese and usage of the isolated isolates as probiotic strains.