Conjugal transfer of bacteriocin plasmids from different genera of lactic acid bacteria into Enterococcus faecalis JH2-2

The lactic acid bacteria (LAB) are of great interest because of their food grade quality and industrial importance. In the recent past, the pediocin PA-1 like bacteriocin was found to be synthesized in cross-species and cross-genera. Hence, the present work was carried out in order to determine the transfer of plasmid encoded pediocin PA-1 like bacteriocin among LAB. The objective of this study is to demonstrate the dissemination of bacteriocin-encoded plasmid from Pediococcus acidilactici NCIM 5424, Enterococcus faecium NCIM 5423 and Lactobacillus plantarum Acr2 to Enterococcus faecalis JH2-2 under in vitro (filter mating method) and in situ (soymilk model) conditions. The fermentation of the soymilk was determined by the selected pediocin producers. E. faecium NCIM 5423 was able to transfer the bacteriocin only under in situ conditions, whereas the native pediocin producer P. acidilactici NCIM 5424 transferred the bacteriocin under both the methods used. The in situ method gave more transfer frequency, ranging from 10^?7 to 10^?4 transconjugants per recipient cell. No conjugal transfer by L. plantarum Acr2 was observed. The physiological conditions like pH and temperature were found to influence the production of bacteriocin in the obtained transconjugants. The results suggest the horizontal gene transfer (HGT) and the natural spread of pediocin PA-1-like bacteriocin among LAB present in their close vicinity by means of conjugation. The dissemination of pediocin PA-1-like bacteriocin under in situ conditions is noteworthy, and such bacteriocin producers can be useful in the fermentation of dairy products and construction of novel cultures.     

Purification and partial characterization of bacteriocin produced by <Emphasis Type="Italic">Lactococcus lactis</Emphasis> ssp. <Emphasis Type="Italic">lactis</Emphasis> LL171

Lactic acid bacteria (LAB) are possessing ability to synthesize antimicrobial compounds (like bacteriocin) during their growth. In this regard, novel bacteriocin compound secreting capability of LAB isolated from Tulum Cheese in Turkey was demonstrated. The synthesized bacteriocin was purified by ammonium sulphate precipitation, dialysis and gel filtration. The molecular weight (≈3.4 kDa) of obtained bacteriocin was confirmed by SDS-PAGE, which revealed single peptide band. Molecular identification of LAB strain isolated from Tulum Cheese was conducted using 16S rDNA gene sequencing as Lactococcus lactis ssp. lactis LL171. The amino acid sequences (KKIDTRTGKTMEKTEKKIELSLKNMKTAT) of the bacteriocin from Lactococcus lactis ssp. lactis LL171 was found unique and novel than reported bacteriocins. Further, the bacteriocin was possessed the thermostable property and active at wide range of pH values from 1 to 11. Thus, bacteriocin reported in this study has the potential applications property as food preservative agent.     

Characterization and application of a native lactic acid bacterium isolated from tannery fleshings for fermentative bioconversion of tannery fleshings

Lactic acid bacteria (LAB) species isolated from limed and delimed tannery fleshings (TF) were evaluated for their fermentation efficiency and antibacterial property. The native LAB isolates efficiently fermented TF and resulted in a fermented mass with antioxidant properties, indicating their potential for effective eco-friendly bioconversion of TF. From among the LAB isolated, a proteolytic isolate showing better antimicrobial spectrum and reasonably good fermentation efficiency was identified as Enterococcus faecium HAB01 based on various biochemical and molecular tests. This isolate afforded a better degree of hydrolysis (81.36%) of TF than Pediococcus acidilactici (54.64%) that was previously reported by us. The bacteriocin produced by E. faecium was found to be antagonistic to several human pathogens including Listeria, Aeromonas, Staphylococcus and Salmonella. Further, E. faecium HAB01 bacteriocin was thermostable and had a molecular weight of around 5 kDa, apart from being stable at both acidic and alkaline conditions. The bacteriocin was unstable against proteases.     

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.     

Production and characterization of a low‐molecular‐weight bacteriocin from Bacillus licheniformis MKU3

Aims: Enhancing production and characterization of a low‐molecular‐weight bacteriocin from Bacillus licheniformis MKU3. Methods and Results: The culture supernatant of B. licheniformis MKU3 exhibited bacteriocin‐like activity against Gram‐positive and ‐negative bacteria and different fungi and yeast. SDS–PAGE analysis of the extracellular proteins of B. licheniformis MKU3 revealed a bacteriocin‐like protein with a molecular mass of 1·5 kDa. This bacteriocin activity was found to be stable under a pH range of 3·0–10·0 and at temperatures up to 100°C for 60 min, but inactivated by proteinase K, trypsin or pronase E. An experimental fractional factorial design for optimization of production medium resulted in a maximum activity of bacteriocin (11 000 AU ml^?1) by B. licheniformis MKU3. Conclusions: A low‐molecular‐weight bacteriocin‐like protein from B. licheniformis MKU3 exhibited a wide spectrum of antimicrobial activity against several Gram‐positive bacteria, several fungi and yeast. A 3·6‐fold increase in the production of bacteriocin was achieved using the culture medium optimized through a fractional factorial design. Significance and Impact of the Study: A bacteriocin with wide spectrum of activity against Gram‐positive bacterial pathogens, filamentous fungi and yeast suggested its potential clinical use. Statistical method facilitated optimization of cultural medium for the improved production of bacteriocin.     

Characterization of Novel Lactobacillus fermentum from Curd Samples of Indigenous Cows from Malnad Region,Karnataka, for their Aflatoxin B1 Binding and Probiotic Properties

Thirty-four isolates of Lactobacillus spp. (LAB) from 34 curd samples were evaluated for their aflatoxin B₁ (AFB₁) binding and probiotic properties. Upon characterization, four LAB isolates (LC3/a, LC4/c, LC/5a, and LM13/b) were found to be effective in removing AFB₁ from culture media with a capacity of above 75%. Staining reaction, biochemical tests, pattern of sugar utilization, and 16s rRNA gene sequence analysis revealed the identity of all the four isolates as L. fermentum. All of them could tolerate acidic pH, salt, and bile, which promise the use of these probiotic bacterial isolates for human applications. These isolates showed poor hydrophobicity and higher auto-aggregation properties. All L. fermentum isolates were found susceptible to gentamycin, chloramphenicol, cefoperazone, ampicillin, and resistant to ciprofloxacin and vancomycin. Results of hemolytic and DNase activity indicated their nonpathogenic nature. Though all L. fermentum isolates found inhibiting the growth of Salmonella ebony, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, maximum inhibition was obtained with isolate LC5/a. Kinetic studies revealed that all four bacteria required a minimum of 2 h to reach stationary phase of AFB₁ binding. AFB₁ binding ability varied from 66 to 85.2% among these four isolates. Bile (0.4%) was significant (P ≤ 0.05) in reducing the AFB₁ binding property of isolates LC3/a, LC4/c, and LM13/b, while increased AFB₁ binding ability was recorded at acidic pH (2.0). AFB₁ binding properties of isolate LC5/a were found least affected by acidic pH and bile. The findings of our study revealed the higher efficiency of L. fermentum isolate LC5/a in reducing the bioavailability of AFB1 in gut, and additionally, it improves the consumers’ health by its various probiotic characters. These beneficial characters, L. fermentum isolates, promise them to use as probiotic formulations alone or in combinations with other beneficial probiotic-bacterial isolates.

     

Determination of the bacterial flora as a microbial control agent of <Emphasis Type="Italic">Toxoptera aurantii</Emphasis> (Homoptera: Aphididae)

Toxoptera aurantii (Homoptera: Aphididae) is one of the most important pests of many agricultural plants such as camellia, cocoa and coffee worldwide. The culturable bacterial flora of the pest was determined to find new microbes that can be used as biocontrol agent against T. aurantii. A total of six bacteria were isolated and identified by a variety of morphological, physiological, biochemical and molecular tests. In addition, an approximately 1,150 bp fragment of the 16S rRNA gene region was sequenced to verify isolate identification. According to the identification studies, the isolates were identified as Bacillus tequilensis Cb1, Chryseobacterium stagni Cb2, Pseudomonas flourescens Cb3, Rahnella aquatilis Cb4, Staphylococcus sp. Cb5 and Cb6. Pathogenicity of the bacterial isolates were carried out against the last instar nymphs of T. aurantii. The highest activity was obtained from Pseudomonas flourescens Cb3 with 50% mortality within 10 days after application (p<0.05). Mortalities of other treatments ranged from 6.6 to 20%. The results presented here show that Pseudomonas flourescens Cb3 appears to be a significant candidate as a possible biocontrol agent against T. aurantii and should be beneficial in the future biocontrol programs of the pest.     

Characterization of a heat stable anti-listerial bacteriocin produced by vancomycin sensitive Enterococcus faecium isolated from idli batter

Lactic acid bacteria (LAB) are known to produce various types of bacteriocins, ribosomally synthesized polypeptides, which have antibacterial spectrum against many food borne pathogens. Listeria monocytogenes, a pathogenic bacterium, is of particular concern to the food industry because of its ability to grow even at refrigeration temperatures and its tolerance to preservative agents. Some of the bacteriocins of LAB are known to have anti-listerial property. In the present study, the bacteriocin produced by vancomycin sensitive Enterococcus faecium El and J4 isolated from idli batter samples was characterized. The isolates were found to tolerate high temperatures of 60°C for 15 and 30 min and 70°C for 15 min. The bacteriocin was found to be heat stable and had anti-listerial activity. The bacteriocin did not lost anti-listerial activity when treated at 100°C for 30 min or at 121°C for 15 min. The bacteriocin lost its antimicrobial activity after treating with trypsin, protinase-K, protease and peptidase.     

Bactericidal and non-cytotoxic activity of bacteriocin produced by Lacticaseibacillus paracasei F9-02 and evaluation of its tolerance to various physico-chemical conditions

This study aims to explore novel lactic acid bacteria (LAB) from breast-fed infants' faeces towards characterizing their antimicrobial compound, bacteriocin. The LAB, Lacticaseibacillus paracasei F9-02 showed strong antimicrobial activity against clinical pathogens. Their proteinaceous nature was confirmed as the activity was completely abolished when treated with proteinaceous enzymes and retained during neutral pH and catalase treatment. The purified bacteriocin showed antimicrobial activity at the minimum inhibitory concentration (MIC) value of 7.56 μg/ml against vancomycin-resistant Enterococcus sp. [vancomycin-resistant enterococcal (VRE)], and methicillin-resistant Staphylococcus aureus (MRSA), 15.13 μg/ml against Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype typhi and 30.25 μg/ml against Shigella flexneri. Present study also proved the bactericidal, non-cytotoxic and non-hemolytic nature of bacteriocin. Additionally, bacteriocin retained their stability under various physico-chemical conditions, broad range of pH (2–10), temperature (40–121°C), enzymes (amylase, lipase and lysozyme), surfactants [Tween-20, 80, 100 and sodium dodecyl sulfate (SDS)], metal ions (CaCl₂, FeSO₄, ZnSO₄, MgSO₄, MnSO₄, CuCl₂) and NaCl (2%–8%). The molecular weight of bacteriocin (~28 kDa) was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), functional and active groups were assessed by Fourier Transform-Infrared (FT-IR). To our knowledge, this is the first study reporting L. paracasei from breast-fed infants' faeces and assessing their antimicrobial compound, bacteriocin. The study results furnish the essential features to confirm the therapeutic potential of L. paracasei F9-02 bacteriocin.     

圈养大熊猫肠道乳酸菌分离及益生特性

【背景】大熊猫数量稀少、繁殖困难,在其生长过程中极易感染消化系统疾病甚至死亡。【目的】分析圈养大熊猫肠道可培养乳酸菌的群落结构与功能,筛选具有益生特性的乳酸菌菌株,为大熊猫消化系统疾病的预防和肠道微生物研究提供理论参考及菌种资源。【方法】采用3种培养基分离大熊猫粪便中的乳酸菌,通过革兰氏染色镜检和过氧化氢试验对分离的菌株进行初步鉴定,基于BOXA1R-PCR图谱遗传多样性选取代表菌株进行16S rRNA基因测序分析并进行主成分分析(principal component analysis, PCA),同时分析乳酸菌菌株安全性和益生特性。【结果】通过初步鉴定共分离获得58株乳酸菌,根据BOXA1R-PCR结果挑选20株菌进行测序,结果显示20株菌分属于明串珠菌属(Leuconostoc)、肠球菌属(Enterococcus)、魏斯氏菌属(Weissella)和链球菌属(Streptococcus)这4个属,主成分分析结果表明不同年龄段的大熊猫肠道乳酸菌群落结构存在差异。20株乳酸菌均不溶血,17株乳酸菌对11种抗生素均敏感;11株菌耐pH值2.0酸性条件,14株菌对0.3%的胆盐具有良好...     

Optimized culture conditions for bacteriocin production by Pediococcus acidilactici LAB 5 and its characterization

A strain of Pediococcus acidilactici LAB 5 was isolated from vacuum-packed fermented meat product, in order to obtain a novel bacteriocin from food-grade organisms. Optimized culture conditions for bacteriocin production in different media (viz., MRS, TGE, TGE + buffer, TGE + Tween 80, and TGE + Tween 80 + buffer) and at different temperatures and pH conditions were reported. TGE + Tween 80 + buffer medium was found to be most effective for bacteriocin production (about 2400 AU/ml) by this strain, when incubated at 37 degrees C for 24 h. Bacteriocin, partially purified by adsorption-desorption method showed molecular mass of 10.3 kDa and produced prominent inhibition zone in activity gel. It showed significant storage stability both at high as well as in low temperatures for up to 6 months and retained its activity in a number of organic solvents, except in 2-mercaptoethanol. The treatment with amylase and lysozyme did not change its activity, but it lost its activity on proteinase K treatment. Antibacterial efficacy of bacteriocin was proved against some food spoilage and human pathogenic bacteria like Enterococcus, Leuconostoc, Listeria, Staphylococcus and Streptococcus.     

Identification and functional properties of dominant lactic acid bacteria isolated at different stages of solid state fermentation of cassava during traditional <Emphasis Type="Italic">gari</Emphasis> production

Culture-based technique was used to study the population dynamics of the bacteria and determine the dominant lactic acid bacteria (LAB) during cassava fermentation. LAB was consistently isolated from the fermented mash with an initial viable count of 6.00 log c.f.u. g⁻¹ observed at 12 h. The aerobic viable count of amylolytic lactic acid bacteria (ALAB) was higher than other group of LAB throughout the fermentation up to 96 h with the highest viable count of 8.08 log c.f.u. g⁻¹. Combination of phenotypic parameters and 16S rDNA gene sequencing identified the dominant group of LAB as Lactobacillus plantarum, L. fermentum and Leuconostoc mesenteroides while the pulse field gel electrophoresis determined that the strains were genotypically heterogeneous. The sugar fermentation profile of the isolates showed that indigestible sugars such as raffinose and stachyose can be fermented by the strains. Information was also generated about the functional properties of the strains. Only strain L. plantarum 9st0 isolate at 0 h of the fermentation produced bacteriocin with antagonism against closely related indicator strains. Quantitatively, the highest amylase activity was produced by strain L. plantarum 7st12, while appreciable amylase was also produced by L. fermentum 1st96. The result of this work showed that selection of mixed starter cultures of bacteriocin- and amylase-producing L. plantarum and L. fermentum will be highly relevant as starter cultures during the intermediate and large scale gari production.     

Phenotypic and genotypic characterization of bacteriocins in clinical <Emphasis Type="Italic">enterococcal</Emphasis> isolates of Tunisia

The presence of bacteriocin structural genes (entA, entB, entP, entQ, entAS-48, entL50A/B, bac31, and cylL) encoding different bacteriocins (enterocin A, enterocin B, enterocin P, enterocin Q, enterocin AS-48, enterocin L50A/B, bacteriocin 31 and cytolysin L, respectively), and the production of bacteriocin activity were analysed in 139 E. faecalis and 41 E. faecium clinical isolates of Tunisia. Forty-eight of 139 E. faecalis isolates (34%) and 7 of 41 of E. faecium isolates (17%) were bacteriocin producers. Sixty-two per cent of the bacteriocin-producing enterococci showed inhibitory activity against L. monocytogenes. Different combinations of entA, entB, entP, and entL50A/B genes were detected among the seven bacteriocin-producer E. faecium isolates, and more that one gene were identified in all the isolates. The entA gene was associated in most of the cases with entB gene in E. faecium isolates. Cyl _LS were the unique genes detected among E. faecalis (in 24 of 48 bacteriocin-producer isolates, 50%). A β-hemolytic activity was demonstrated in 19 of the 24 cyl _LS -positive E. faecalis isolates (79%), this activity being negative in the remaining five isolates. The presence of different bacteriocin structural genes and the production of antimicrobial activities seems to be a common trait of clinical enterococci.     

Purification and characterization of a bacteriocin from Lactobacillus rhamnosus L34

Bacteriocins are ribosomally synthesized peptides having considerable potential as a food preservative because of their strong antagonistic activity against many food spoilage and pathogenic organisms. A bacteriocin from Lactobacillus rhamnosus isolates was purified using ammonium sulphate precipitation and molecular exclusion chromatography techniques. Ammonium sulphate precipitation resulted in higher yield of bacteriocin, but the specific activity and fold purification were higher for molecular exclusion chromatography. The bacteriocin exhibited inhibition against food-borne pathogens and spoilage microorganisms, including both Gram-positive and -negative bacteria. Amylase, lipase and catalase did not alter the antimicrobial activity but proteolytic enzymes inactivated the bacteriocin. It was heat stable and exhibited activity in a pH range of 2–8 with maximum activity at pH 5.0. Molecular weight of bacteriocin was found to be ~5.6 kDa using SDS-PAGE. HPLC profile showed a single peak further attesting the purity of the bacteriocin.     

Characterization and antioxidant ability of potential probiotic lactic acid bacteria in ogi liquor and lemon juice-ogi liquor

Purpose

Ogi is an indigenous edible fermented cereal slurry but the steep liquor is usually wasted or administered as therapeutic to suppress certain illnesses. The combination of lemon juice and ogi steep liquor (OSL) is known to possess bioactive metabolites.

Method

This study evaluated potential probiotic lactic acid bacteria (LAB) in different OSL (Zea mays, Sorghum bicolor, and Pennisetum glaucum L.) and lemon juice-ogi steep liquor (LJOSL) based on low pH, bile and lysozyme tolerances, hydrophobicity and auto-aggregation, antibiotic, cholesterol removal, exopolysaccharide production, β-galactosidase, and antimicrobial and hemolytic activities using standard methods. Presumptive LAB were sequenced and assayed for radical scavenging using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and lipid peroxidation inhibitory (LPI) tests.

Results

Presumptive LAB counts were higher in maize OSL (0 h:5.09 log CFU/ml) and combined cereal OSL (24–48 h:7.65 and 7.72 log CFU/ml) but decreased in all steep liquors at 72 h, except in millet OSL (7.72 log CFU/ml). A total of 120 LAB isolates were randomly selected. Based on pH and bile tolerances, 14 isolates were comparable to reference strains. All these isolates demonstrated probiotics properties except for three that did not show γ-hemolysis. Sequenced LAB isolates were identified as Lactobacillus plantarum, Lactobacillus fermentum, Pediococcus pentosaceus, and Weissella cibara. DPPH activities of LAB gradually increased during fermentation with the highest activity of DPPH (58.77%) and LPI (57.94%) activity in L. plantarum. Strong correlations were found between DPPH and LPI in all the selected isolates.

Conclusion

The antioxidant property of probiotic LAB in OSL and LJOSL could contribute to its therapeutic nature.

     

Purification and Characterization of Warnericin RB4, Anti-Alicyclobacillus Bacteriocin, Produced by Staphylococcus warneri RB4

In this study we characterized a bacteriocin, warnericin RB4, produced by Staphylococcus warneri RB4. Warnericin RB4 activity was completely inactivated by trypsin and actinase E. The activity was stable at 100°C for 15 min, and had a pH range of 2 to 6. S. warneri RB4 showed antibacterial activity against only Alicyclobacillus acidoterrestris, A. acidocaldarius, and Micrococcus luteus, among 34 bacterial species tested. The amino acid sequence of the purified bacteriocin contained 27 amino acid residues (K-K-K-S-G-V-I-P-X-V-X-H-D-X-H-M-N-X-F-Q-F-V-F-X-X-X-S). The molecular mass of the bacteriocin was estimated to be 2,958.2 Da by ESI-MS. These results show that the Warnericin RB4 exhibiting specific antibacterial activity against thermo-acidophiles, Alicyclobacillus spp., is a Nukacin ISK-1 or closely related bacteriocin, classified with class IA (Lacticin 481 types). This is the first report that Warnericin RB-4 is effective to inhibit the growth of causative microorganisms of spoilage in various acidic drinks. Warnericin RB4 might prove useful in fruit juices and fruit juice–containing drinks.     

Detection, purification and efficacy of warnerin produced by Staphylococcus warneri

Summary Three strains of Staphylococcus warneri (FM10, FM20 and FM30) isolated from meat samples were investigated for their ability to synthesize bacteriocin. All the tested strains produced warnerin, a new peptide bacteriocin; which inhibits the growth of a large number of Gram-positive and Gram-negative bacteria. The inhibitory effect of warnerin produced by the FM20 isolate was high when compared to the other isolates. The results on the effect of carbon sources, nitrogen sources, pH, temperature, incubation time and surfactant (tween 80) inferred that the bacteriocin production was high in medium supplemented with 1% glucose (12,800 AU/ml), 1% urea (6800 AU/ml), and 0.5% Tween 80 (25,600 AU/ml). The higher productivity of bacteriocin was registered during 12 h of incubation in the medium pH 6.5 at 37 °C temperature. Among the various indicator strains tested, Staphylococcus aureus was more sensitive to the bacteriocin activity. Partially purified warnerin exhibited a single band on SDS-PAGE with an apparent molecular weight of 2500 Da. Warnerin, the antibacterial compound was determined as a proteinaceous substance, since it lost its activity when pepsin was added.     

Effect of prebiotics on bacteriocin production and cholesterol lowering activity of <Emphasis Type="Italic">Pediococcus acidilactici</Emphasis> LAB 5

The in vitro influence of three prebiotics viz. mannitol, maltodextrin and sorbitol was evaluated on probiotic aspects like bile salt tolerance, cholesterol lowering efficiency and bacteriocin production of the strain, Pediococcus acidilactici LAB 5 which was isolated from vacuum packed fermented meat product. Optimum temperature for bacteriocin production in MRS medium was 37°C. The strain deconjugated bile salt (sodium taurocholate) to 607.66 ± 10.894 μg/ml from initial bile salt concentration 3 mg/ml. In vitro cholesterol removal capability of the strain P. acidilactici LAB 5 was 62 ± 2.742 μg/ml. Prebiotic sorbitol had a positive influence on the probiotic parameters like better cell growth, bacteriocin production and cholesterol removal capability. Anaerobic condition had influenced largely on bile salt deconjugation, cholesterol removal and bacteriocin production. Synbiotic treatment of P. acidilactici LAB 5 with sorbitol for 1 month lowered the plasma cholesterol level to 176.34 ± 12.66 μg/ml in comparison to untreated one (208.76 ± 20.27 μg/ml) in Swiss albino mice. Intestinal adherence of P. acidilactici LAB 5 was also more in synbiotic condition than only in probiotic and control treatments.     

Characterization and Structure Analysis of a Novel Bacteriocin,Lacticin Z,Produced by Lactococcus lactis QU 14

A novel bacteriocin, lacticin Z, produced by Lactococcus lactis QU 14 isolated from a horse’s intestinal tract was identified. Lacticin Z was purified through a three step procedure comprised of hydrophobic-interaction, cation-exchange chromatography, and reverse-phase HPLC. ESI-TOF MS determined the molecular mass of lacticin Z to be 5,968.9 Da. The primary structure of lacticin Z was found to consist of 53 amino acid residues without any leader sequence or signal peptide. Lacticin Z showed homology to lacticin Q from L. lactis QU 5, aureocin A53 from Staphylococcus aureus A53, and mutacin BHT-B from Streptococcus rattus strain BHT. It exhibited a nanomolar range of MICs against various Gram-positive bacteria, and the activity was completely stable up to 100 °C. Unlike many of other LAB bacteriocins, the stability of lacticin Z was emphasized under alkaline conditions rather than acidic conditions. All the results indicated that lacticin Z belongs to a novel type of bacteriocin.     

Identification and Characteristics of Nisin Z-Producing <Emphasis Type="Italic">Lactococcus lactis</Emphasis> subsp. <Emphasis Type="Italic">lactis</Emphasis> Isolated from Kimchi

We isolated bacteriocin-producing Lactococcus lactis subsp. lactis from Kimchi. The bacteriocin inhibited strains of Clostridium perfringens, C. difficile, Listeria monocytogenes, vancomycin-resistant Enterococcus, and one out of four methicillin-resistant Staphylococcus aureus strains, as well as some closely related lactic acid bacteria. In tricine-SDS-PAGE, the bacteriocin migrated with an apparent molecular weight of about 4 kDa to the same location as nisin A and crude nisin Z. The gene encoding this bacteriocin was found to be identical to that of nisin Z with direct PCR sequence methods. The inhibitory activity was stable against heat and pH, but it was lost at 100°C for 1 h and at 121°C for 15 min. The bacteriocin was inactivated by proteolytic enzymes, but was not affected by lysozyme, lipase, catalase, or β-glucosidase. There were some differences in characteristics from those of nisins described previously. Received: 21 June 2002 / Accepted: 22 July 2002