Bacteriocinogenic Activity Research Articles

Evaluation of Rye Bran Enzymatic Hydrolysate Effect on Gene Expression and Bacteriocinogenic Activity of Lactic Acid Bacteria

Lactic acid bacteria (LAB) bacteriocins can be considered as a bio-preservatives and an alternative to antibiotics, but the high manufacturing costs limit their commercial application. The screening of LAB strains for bacteriocinogenic activity was carried out and the effect of rye bran enzymatic hydrolysate (RBEH) on gene expression and bacteriocin production was evaluated. qPCR and RT-PCR was applied for bacteriocin gene detection and their expression quantification. The agar diffusion technique with the test strains of Bacillus spp., Staphylococcus spp. and Salmonella enterica was performed for antimicrobial activity assessment of LAB cultivated in MRS broth and RBEH (processed with proteases and cellulases). The genes of different bacteriocins were revealed for thirteen out of eighteen LAB strains, while the antimicrobial activity was detected only for four of them. The strains of Lactobacillus paracasei VKPM B-11657 and L. salivarius VKPM B-2214 with unnamed class IIb bacteriocin gene demonstrated the widest spectrum of activity. The growth patterns and bacteriocin gene expression differed between both strains and media. The activity of cell-free supernatants after cultivation in RBEH was slightly lower. However, the test strain of S. epidermidis was inhibited by L. paracasei cultivated in RBEH but not in MRS. Thus, rye bran can be applied as a sole source of nutrients for LAB fermentation and bacteriocin production.

Antistaphylococcal and antioxidant activities of bacteriocinogenic lactic acid bacteria and essential oil in goat coalho cheese.

Bacteriocinogenic lactic acid bacteria (LAB) isolates and Croton heliotropiifolius essential oil (EO) were used to inhibit Staphylococcus aureus subsp. aureus and enhance the antioxidant action in goat coalho cheese (GCC). Lactic acid bacteria isolates were selected for their inhibitory capacity against S. aureus subsp. aureus, safety, existence of bacteriocin-encoding genes, bacteriocinogenic activity, and its antistaphylococcal action. The staphylococcal inhibition capacity of C. heliotropiifolius EO was also verified. Three cheeses were prepared containing S. aureus subsp. aureus (GCC SA), S. aureus subsp. aureus + LAB (GCC SA + LAB), and S. aureus subsp. aureus + EO (GCC SA + EO). Samples were analysed on days 0, 7, 14 and 21. Based on the screening, three LAB isolates were selected and identified as Enterococcus faecium. In GCC, the smallest population of S. aureus subsp. aureus was found until the 17th in the GCC SA + EO and from the 18th in the GCC SA + LAB. Total phenolic content and antioxidant activity increased over time in GCCs. Autochthonous bacteriocinogenic LAB and C. heliotropiifolius EO are natural resources of the Caatinga, an exclusively Brazilian biome that predominates in the northeast of the country, with the potential to reduce the presence of S. aureus and increase the antioxidant activity in the GCC. Goat coalho cheese is a product of cultural importance in northeastern Brazil. The process of obtaining the GCC is manual, and there is a high frequency of S. aureus in the product. Resources of the Caatinga with biofunctional properties can be tested to reduce the risk of staphylococcal toxins, and contribute to the nutritional value of the GCC, maintaining regional characteristics and respecting the local cultural tradition. LAB and C. heliotropiifolius EO contribute to the incorporation of bioactive substances and microbiological quality, generating a value-added GCC with exclusive resources of the Caatinga.

Characterization of technological properties of lactic acid bacteria isolated from Turkish Beyaz (white) cheese

A total 144 lactic acid bacteria (LAB) strains were chosen and identified from 20 samples of Turkish Beyaz cheeses to be used as a starter or bioprotective culture. Genotypic characterization of these isolates revealed the presence of distinct LAB strains belonging to 15 different species including Enterococcus faecium, Streptococcus lutetiensis, Enterococcus faecalis, Lactococcus lactis, Lacticaseibacillus paracasei, Lactiplantibacillus plantarum, Streptococcus macedonicus, Lactobacillus curvatus, Lacticaseibacillus paracasei spp. tolerans, Enterococcus durans, Lactobacillus delbrueckii spp. lactis, Enterococcus italicus, Leuconostoc pseudomesenteroides, Lactiplantibacillus paraplantarum, and Pediococcus parvulus. The LAB strains were characterized according to their technological properties. In conclusion, many of the isolated LAB have important technological properties and in particular, L. lactis L52 and S. macedonicus L36 were found to be the most promising starter culture candidates due to their high acid-producing capacity. In addition, based on the results of antimicrobial and bacteriocinogenic activity, L. lactis L54 strain could be used as a bioprotective culture. Novelty impact statement This study is one of the most comprehensive research revealing the LAB diversity of Turkish Beyaz cheese, and it has been shown that many of the isolated LAB strains might have important technological properties to be used in white brined cheese production.

Natural Bioactive Compounds in Organic and Conventional Fermented Food.

Compared to conventional agriculture, organic farming is believed to provide a higher nutritional and health value in its products due to the elimination of harmful contaminants (pesticides, nitrates, heavy metals, etc.). Numerous studies have been conducted to show how the production system affects the quality of food in terms of the content of bioactive compounds. The aim of this study was to compare the content of some bioactive compounds (vitamin C, β-carotene, Ca content) and lactic acid bacteria (LAB) number and their bacteriocinogenic activity in organic and conventional fermented food. Although the results do not provide an unambiguous conclusion regarding the superiority of one production system over the other, the LAB number in organic pickled carrot juice, sauerkraut, yogurt, and kefir was higher than in their conventional counterparts. Their bacteriocinogenic potential against selected pathogens was also higher in most organic products. Organic vegetables contained significantly more vitamin C, and the calcium content in the organic yogurt was higher compared to the conventional version of the product. Relatively similar concentrations of ß-carotene for both production systems were found in carrot juice, while in organic pickled beet juice, there was five-fold less ß-carotene than in conventional juice.

Effects of lactic acid bacteria with bacteriocinogenic potential on the chemical composition and fermentation profile of forage peanut (Arachis pintoi) silage

The objectives of this study were to evaluate the effect of lactic acid bacteria (LAB) with bacteriocinogenic activity isolated from stylo silages on the microbial population, chemical composition and fermentation profile of forage peanut silage (FPS) and to identify LAB species in forage peanut and its silages based on the 16 S rRNA sequence analysis. The experiment was conducted in a completely randomized design with a 5 × 6 factorial arrangement (five inoculants (I) × six fermentation periods (P)) and three replicates. The following inoculants were evaluated: without inoculant (CTRL); a commercial inoculant at a dose of 107 colony forming units (cfu) g-1 fresh matter (CI1); a commercial inoculant at a dose of 105 cfu g-1 fresh matter (CI2); Pediococcus acidilactici strain 10.6 (S1); and Pool of bacteriocinogenic strains (POOL), including S1, P. pentosaceus strain 6.16 and P. acidilactici strain 10.4. The fermentation periods were 1, 3, 7, 14, 28 and 56 days. The largest LAB populations were observed in silages treated with S1 (8.66 log cfu g-1) and POOL (8.69 log cfu g-1). At the end of the fermentation period, a higher content of dry matter (222.53 g kg-1) and lactic acid (66.30 g kg-1) and lower values of pH (4.76) and acid detergent insoluble nitrogen (9.50% of total nitrogen) were observed for silage treated with S1. The screening of LAB from forage peanut silage revealed that P. pentosaceus was the predominant species. In addition, the wild strain of P. acidilactici 10.6 established a desirable microbial population during the fermentation process reflecting a highest lactic acid concentration and lowest pH values after 56 days of fermentation.

Biodiversity and technological features of Weissella isolates obtained from Brazilian artisanal cheese-producing regions

Weissella spp. strains (n = 57) were isolated from different Brazilian food-related environments and characterized based on their genetic profiles and technological potential. PFGE and Rep-PCR revealed the high level of biodiversity among isolates: PFGE grouped the isolates in three major profiles (similarity from 60 to 80%), while rep-PCR characterized the isolates as belonging to a single profile. Based on PFGE, isolates with identical pulsotypes were found within a same geographical region (Campo das Vertentes, Minas Gerais state). Based on these profiles, 26 isolates were selected and characterized based on their inhibitory and bacteriocinogenic activity against Listeria monocytogenes ATCC 15313, Staphylococcus aureus subsp. aureus ATCC 6538, Salmonella enterica subsp. enterica serovar Typhimurium ATCC 14028 and Escherichia coli ATCC 11229. Most isolates (n = 20) were able to inhibit the targets through organic acids. Most of the isolates (n = 12) were able to produce diacetyl, proteases, and/or coagulating milk, but none were able to produce exopolysaccharides. Isolate 16, in particular, was characterized as possessing high acidification ability, diacetyl and protease production, with promising technological potential in the dairy industry. The obtained results allowed the understanding of the Weissella spp. strains role as starter cultures in the dairy industry.

Safety evaluation and bacteriocinogenic potential of Pediococcus acidilactici strains isolated from artisanal cheeses

Pediococcus acidilactici ST1607V, ST2104V and ST3105V, isolated from a Brazilian artisanal cheese expressed bacteriocins with high inhibitory activity against several strains of Listeria monocytogenes and Enterococcus spp., but not against most of the other tested lactic acid bacteria (LAB). Bacteriocinogenic activity against L. monocytogenes ATCC7644 was expressed with a high titre of 51200 AU/mL (ST1607V and ST2104V) and 25600 AU/mL (ST3105V), when cultured in MRS. Bacteriocins produced by strains ST1607V, ST2104V and ST3105V presented a bactericidal mode of action against L. monocytogenes ATCC7644 and Enterococcus faecium ATCC19434. DNA of the studied LAB strains was obtained and subjected to PCR assays targeting more than 50 genes related to biogenic amines production (histidine, tyrosine and ornithine decarboxylases), virulence (sex pheromones, gelatinase, cytolysin, hyaluronidase, aggregation substance, enterococcal surface protein, endocarditis antigen, adhesion of collagen, integration factors) and antibiotic resistance (vancomycin, tetracycline, erythromycin, gentamicin, chloramphenicol, bacitracin). A few safety-related genes were detected in some strains, indicating their safety for application in fermented food products. Special attention should be given to the presence of possible virulence factors, in addition to the production of biogenic amines and antibiotic resistance. Additional in vitro and in vivo experiments could be designed for future evaluation of possible expression of detected virulence genes.

Streptococcus Salivarius Subsp Salivarius BIO5 - Toxicity Evaluation of a Possible Probiotic Strain

Probiotic bacteria, which are traditionally studied to aid intestinal functions, are also currently being researched for benefits in other parts of the body such as the oral cavity. In the case of throat infections caused by bacteria, which traditional treatment involves antibiotics, some researchers are studying the possibility of introducing special strains of commensal bacteria into the mouth that can specifically inhibit the tonsillitis agent Streptococcus pyogenes for both prevention and treatment of such disease. A PCR assay was used to identify Streptococcus salivarius subsp salivarius. Therefore, tests for the complete absence of toxicity of these strains are required to ensure their safe use in human trials. In this research, we evaluated the new Streptococcus salivarius subsp salivarius BIO5 strain for toxicity factors, as follows: clinical, ophthalmic lesions, behavioral observations, mortality, anatomopathological examination, biopsy, hematology, serum biochemistry, and urine analysis. This strain, isolated from the oral cavity and with bacteriocinogenic activity against S. pyogenes, showed a complete absence of toxicity and thus it may be used in replacement therapy as a probiotic.

Antagonistic effect and bacteriocinogenic activity of Lactic Acid Bacteria isolated from <i>Sorghum bicolor</i>-based ‘ogi’ on food borne bacterial pathogens from cabbage

Background: Lactic acid bacteria (LAB) are important organisms recognized for fermentative ability as well as health and nutritional benefits. A large number of bacteriocins from LAB have been characterized and a number of studies have indicated the potential usefulness of bacteriocin in food preservative. The objective of this study was to evaluate the antagonistic effects and bacteriocinogenic activity of LAB isolated from Sorghum bicolor-based ‘ogi’ against selected food borne bacteria from cabbage samples. Methodology: Five samples of Sorghum bicolor-based ‘ogi’ and 5 samples of suspected infected cabbage heads were randomly collected using sterile water proof material from Abakpa main market, Abakaliki, and processed at the Applied Microbiology Laboratory of Ebonyi State University, for isolation of LAB and food borne pathogen by conventional culture and biochemical identification tests. Antagonistic effects of LAB and its bacteriocinogenic activity were determined by agar well diffusion test. Results: Three different Lactobacillus species designated A, B, and C, were isolated from the Sorghum bicolorbased ‘ogi’ and 5 bacterial species were isolated from cabbage heads; Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella, and Shigella species. The Lactobacillus species had inhibitory effect against S. aureus, E. coli, and Shigella species with inhibition zone diameters (IZD) of 19 mm, 10 mm, and 10 mm respectively. The crude bacteriocin extracts from the Lactobacillus species showed higher inhibitory activity against tested bacterial isolates at 10-1 (0.1ml) than at 10-2 dilution (0.01ml), and the inhibitory activity was higher at pH 2 than pH 6 and 7, with no activity at pH 8. Conclusion: This study showed that LAB and its extracted bacteriocin demonstrated in vitro inhibitory activity against food borne pathogens isolated from cabbage heads. There is the need to further characterize the active components of the bacteriocin for possible commercial use as preservatives and potential source of new antimicrobial agent. Keywords: Lactic acid bacteria, bacteriocin, cabbage, fermented food, ‘ogi’

Lactobacillus curvatus UFV-NPAC1 and other lactic acid bacteria isolated from calabresa, a fermented meat product, present high bacteriocinogenic activity against Listeria monocytogenes

BackgroundBacteriocins produced by lactic acid bacteria (LAB) can be considered as viable alternatives for food safety and quality, once these peptides present antimicrobial activity against foodborne pathogens and spoilage bacteria. Fermented foods, such as artisanal sausages and cured meats, are relevant sources of LAB strains capable of producing novel bacteriocins, with particular interest by the food industry.ResultsThree LAB strains (firstly named as Lactobacillus curvatus 12, L. curvatus 36 and Weissella viridescens 23) were obtained from calabresa by presenting promising bacteriocinogenic activity, distinct genetic profiles (rep-PCR, RAPD, bacteriocin-related genes) and wide inhibitory spectrum. Among these strains, L. curvatus 12 presented higher bacteriocin production, reaching 25,000 AU/mL after incubation at 25, 30 and 37 °C and 6, 9 and 12 h. Partially purified bacteriocins from L. curvatus 12 kept their inhibitory activity after elution with isopropanol at 60% (v/v). Bacteriocins produced by this strain were purified by HPLC and sequenced, resulting in four peptides with 3102.79, 2631.40, 1967.06 and 2588.31 Da, without homology to known bacteriocins.ConclusionsLAB isolates obtained from calabresa presented high inhibitory activity. Among these isolates, bacteriocins produced by L. curvatus 12, now named as L. curvatus UFV-NPAC1, presented the highest inhibitory performance and the purification procedures revealed four peptides with sequences not described for bacteriocins to date.

Characterization of the bacteriocin produced by Enterococcus italicus ONU547 isolated from Thai fermented cabbage.

Seventy-eight isolates of lactic acid bacteria from Ukraine and Thailand were screened for bacteriocinogenic activity against indicator strain Lactobacillus sakei subsp. sakei JCM 1157. One isolate showed an antagonistic activity of cell-free supernatant eliminated after the treatment with Proteinase K. Based on 16S rRNA gene sequence, this isolate was identified as Enterococcus italicus. Bacteriocin produced by this strain showed antimicrobial activity against L. sakei subsp. sakei JCM 1157, Brochothrix thermosphacta DSMZ 20171, and Listeria ivanovii subsp. ivanovii DSMZ 20750 in agar well diffusion assay. This bacteriocin was cationic and hydrophobic. The partially purified bacteriocin was thermostable, while heating of cell-free supernatant increased its activity more than twofold. Molecular mass of the partially purified bacteriocin as determined by SDS-PAGE differed from enterocin A and B previously known for E. italicus. Concentrated bacteriocin decreased the level of biofilm formation in L. sakei subsp. sakei JCM 1157 and Pseudomonas aeruginosa PAO1 in 52.5 and 48.0%, respectively (p< 0.05). We suggest that the studied bacteriocin could be a perspective antibiofilm agent in food conservation and medicine.

Antagonism of Bacteria from Dog Dental Plaque against Human Cariogenic Bacteria.

Dental caries are a process of demineralization and destruction of human teeth. They originate through many factors and are associated with biofilm formation, which consists of bacteria adhered to the teeth that form a structurally and functionally organized mass called dental plaque. Both the presence of Streptococcus mutans and the frequent consumption of sucrose correlate with a higher prevalence of caries in humans. In dogs, however, the incidence of this disease is low, due to factors such as differences in dental microbiota and/or their low consumption of sucrose. This work evaluated the antagonism of bacteria from dog's dental plaque against S. mutans, for the identification of producing strains of biotechnological products for use in preventing caries. This study used 95 bacterial isolates of canine dental plaque from the Veterinary Department at the Federal University of Viçosa, Minas Gerais, Brazil. A spot-on-the-lawn method was performed using Brain Heart Infusion agar with catalase for an initial identification of the antagonistic activity. Additional tests were conducted on the isolates classified as antagonists for confirmation of the activity, using modified Mann-Rogosa-Sharpe medium containing low dextrose concentration. These isolates were incubated at 37°C for 24 hours in anaerobiosis. The peptide nature of inhibition was evaluated using the following proteinases: proteinase K from Tritirachium album, bovine pancreatic trypsin, and type XII-A α-amylase from Bacillus licheniformis. In the initial identification of those strains exhibiting antimicrobial activity, 14 were classified as antagonists. One of the isolates (Bacillus sp.) indicated bacteriocinogenic activity, with a deformed inhibition halo on S. mutans by the addition of trypsin. These results suggest that this bacterial isolate may be applicable to biotechnological use to combat the main etiological agent of caries in humans. Further studies are needed to evaluate the bacteriocinogenic nature of the antimicrobial activities of the other 13 antagonistic bacterial isolates.

Optimization and some characteristics of bacteriocin produced by Enterococcus sp. CM9 collected from Mauritanian Camel milk

The use of bacteriocin as a bioconservation is very promising in the agri-food industry to substitute the chemical preservatives. The production of bacteriocin by lactic acid bacteria (LAB) depending on various conditions, the purpose of the present work was to assess the effect of some ingredients of medium on the bacteriocin production. Twenty-four strains of LAB of the genera Leuconostoc, Lactobacillus, and Enterococcus, isolated from camel milk, were tested for antibacterial activity and bacteriocin production. Among these strains, three isolates showed bacteriocinogenic activity, two Enterococcus strains (bacteriocin CM9, bacteriocin CM18), and one Leuconostoc strain (bacteriocin CHBK310). The bacteriocin produced by Enterococcus sp CM9 was subject of optimisation study. The modified MRS with nitrogen sources in media containing tryptone, meat extract and yeast extract and with potassium sources in media containing 2% of K2HPO4 allowed higher activity with inhibition zone of 10 mm and this production remained stable at incubation temperatures from 25 to 40°C with an inhibition zone which reached 12 mm at 25°C. The diffusion of this bacteriocin in the neutrality condition, allowed a better evaluation of its inhibitory effect. The activity of the bacteriocin was not affected, neither by acidic or basic pH nor by heat treatments, its activity remaining stable even after 2 weeks at -20 and 4°C. The bacteriocin CM9 belonged to class II, had a molecular weight of 7.6 kDa. These results indicated that the growth and diffusion conditions have a role in the bacteriocin production and its activity.

Antibacterial and Synergistic Activity Against β-Lactamase-Producing Nosocomial Bacteria by Bacteriocin of LAB Isolated From Lesser Known Traditionally Fermented Products of India

There is an ever-growing need to control antibiotic-resistance owing to alarming resistance to commonly available antimicrobial agents for which contemporary and alternative approaches are being explored. The present study assessed the antibacterial activity of bacteriocins from lactic acid bacteria (LAB) from lesser known traditionally fermented products of India for their synergistic potential with common antibiotics against clinical β-lactamases producing pathogens. A total of 84 isolates of LAB were screened for their antibacterial efficacy against Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Bacillus cereus as well as against clinical pathogens harbouring β-lactamase genes such as blaCTX-M,blaVIM,blaIMP, blaSHV and blaNDM. Synergistic activity of bacteriocins were determined in combination with antibiotics namely, cefotaxime, polymyxin B, imipenem and tigecycline. Purified bacteriocins from Lactobacillus, Pediococcus and Enterococcus inhibited the growth of β-lactamase harbouring clinical pathogens which significantly higher inhibitions when compared with antibiotics alone. Minimum inhibitory concentration of the extracts ranged from 6.66 to 26.66 mg/ml and 10 to 33.33 mg/ml for Pediococcus pentosaceus LU11 and Lactobacillus plantarum LS6. The bacteriocinogenic activity of LAB opens scope for bioprospection of antibacterial components in the current struggle against increasing pandrug resistance and slowing down the expansion of multi-drug resistance.

Evaluation of bacteriocinogenic activity, safety traits and biotechnological potential of fecal lactic acid bacteria (LAB), isolated from Griffon Vultures (Gyps fulvus subsp. fulvus).

BackgroundLactic acid bacteria (LAB) are part of the gut microbiota and produce ribosomally synthesized antimicrobial peptides or bacteriocins with interest as natural food preservatives and therapeutic agents. Bacteriocin-producing LAB are also attractive as probiotics. Griffon vultures (Gyps fulvus subspecies fulvus) are scavenger birds that feed almost exclusively on carrion without suffering apparent ill effects. Therefore, griffon vultures might be considered a reservoir of bacteriocin-producing lactic acid bacteria (LAB) with potential biotechnological applications.ResultsGriffon vulture feces were screened for LAB with antimicrobial activity, genes encoding bacteriocins, potential virulence determinants, susceptibility to antibiotics, genotyping and characterization of bacteriocins. In this study, from 924 LAB evaluated 332 isolates (36 %) showed direct antimicrobial activity against Gram-positive bacteria only. The molecular identification of the most antagonistic 95 isolates showed that enterococci was the largest LAB group with antimicrobial activity (91 %) and E. faecium (40 %) the most identified antagonistic species. The evaluation of the presence of bacteriocin structural genes in 28 LAB isolates with the highest bacteriocinogenic activity in their supernatants determined that most enterococcal isolates (75 %) encoded multiple bacteriocins, being enterocin A (EntA) the largest identified (46 %) bacteriocin. Most enterococci (88 %) were resistant to multiple antibiotics. ERIC-PCR and MLST techniques permitted genotyping and recognition of the potential safety of the bacteriocinogenic enterococci. A multiple-step chromatographic procedure, determination of the N-terminal amino acid sequence of purified bacteriocins by Edman degradation and a MALDI TOF/TOF tandem MS procedure permitted characterization of bacteriocins present in supernatants of producer cells.ConclusionsEnterococci was the largest LAB group with bacteriocinogenic activity isolated from griffon vulture feces. Among the isolates, E. faecium M3K31 has been identified as producer of enterocin HF (EntHF), a bacteriocin with remarkable antimicrobial activity against most evaluated Listeria spp. and of elevated interest as a natural food preservative. E. faecium M3K31 would be also considered a safe probiotic strain for use in animal nutrition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0840-2) contains supplementary material, which is available to authorized users.

ATIVIDADE ANTIMICROBIANA DE BACTÉRIAS ENDOFÍTICAS ISOLADAS DE Jacaranda decurrens Cham. (CAROBINHA-DO-CAMPO)

Bacteriocins are antibiotics classified as natural products, in other words, secondary metabolites produced by bacteria. Endophytic, micro-organisms that have plants as hosts in at least one life stage, are a good example of bacteriocin producers. The aim of this work was to evaluate the antimicrobial activity probably due to bacteriocin production by endophytic bacteria isolated from Jacarranda decurrens Cham. against different indicator strains and the bioactive metabolites sensibility to temperature (7580oC) and to trypsin in two different media. It was used 10 endophytic bacterial isolates previously isolated from Jacaranda decurrens Cham. 70% of the isolated presented antimicrobial activity, evidenced by inhibition halos in agar plates against at least one of the 15 indicators strains. The antimicrobial compounds generated by the isolates CAR 4, CAR 5 and CAR 7 were thermolabile and resistant to trypsin. The metabolites produced by CAR 6 were sensible to the heat and the enzymatic treatment and the isolates CAR 2, CAR 4, CAR 5 and CAR 7 also produced substances sensible to these conditions. The production of the antimicrobial compounds just happened in media 523 and it was not observed the presence of bacteriophages. Substances with bacteriocinogenic activity and with broad spectrum of action against pathogenic organisms was produced by the endophytic bacteria from the medicinal plant, thus exhibiting interesting potential to be applied as antimicrobials and in biological control.

English

The aims of this study were to identify bacteriocinogenic activity in 13 enterococci isolated from fecal samples of wild South American (Arctocephalus australis) and Subantarctic fur seals (Arctocephalus tropicalis); to determine the physicochemical characteristics and antimicrobial spectrum of antimicrobial compounds against Gram-positive and Gram-negative bacteria; and to evaluate the presence of bacteriocin structural genes by PCR. Out of 13 enterococci screened for antimicrobial activity, five enterococci showed activity against Listeria monocytogenes ATCC 35152, an important pathogen linked to food. Of these, only the E. mundtii strain J5 maintained the activity after the pH was adjusted (pH 6.5). The activity of antimicrobial compounds from the E. mundtii strain J5 (ACs-J5) was lost after proteolytic enzyme treatment; however, the activity was maintained after heat, pH (acidic and basic conditions) and chemical treatment. ACs-J5 showed narrow spectrum activity. Only the mundticin KS gene was detected in the J5 strain and no plasmid was present. In conclusion, the properties presented by ACs-J5 make it a valuable biopreservative in food industries in avoiding pathogenic microorganisms such as L. monocytogenes and it should be a good candidate for probiotic application. Key words: Antimicrobial compounds, Enterococcus mundtii, wild fur seal, antilisterial activity.

English

The detection of bacteriocinogenic potential of Enterococcus sp. isolates from Algerian raw milk coded LO4 and LO12 and from traditional butter coded BRO2 was carried on M17 buffered medium. PCR amplification of Enterococcus sp. DNA using specific enterococcal primers gave 733 bp fragments. The phylogenetic analysis using the neighbour joining method further supported the identification of the three strains as Enterococcus faecium . These bacteria were bacteriocinogenic against Pseudomonas sp , Proteus mirabilis and E. faecium . Lyophilisate extracts were tested for sensitivity to enzymes, heating and effect of pH. Complete inactivation in bacteriocinogenic activity was observed after treatment with proteolytic enzymes. The antibacterial activity from E faecium LO12 was stable (1280 AU/ml) for range pH 2 to 12. Maximal activity from BRO2 strain was at pH 7 (20480 AU/ml) and from LO4 strain was at pH 7 and 6 (2560 AU/ml). Antibacterial activities of E. faecium BRO2 (5120 AU/ml) and E. faecium LO12 (640 AU/ml) remained stable at 60°C for 30 min. The antibacterial activity of . E faecium LO4 was stable at 100°C for 30 min (5120 AU/ml).

Pediococcus pentosaceus SB83 as a potential probiotic incorporated in a liquid system for vaginal delivery.

Pediococcus pentosaceus SB83 is a bacteriocinogenic culture having potential use as a vaginal probiotic. The objective of this study was to evaluate the behaviour of P. pentosaceus SB83 incorporated in a liquid system for eventually formulating a gel for vaginal delivery. The vaginal probiotic incorporated into glycerol was able to survive in simulated vaginal fluid at normal vaginal pH (4.2) and at pH of vaginal infections (5.5 and 6.5). The probiotic can be stored at 4 °C for a longer period of time than at room temperature, however, after 13 weeks of storage at low temperature, there was a total loss of viable cells. The probiotic strain incorporated into glycerol showed bacteriocinogenic activity in simulated vaginal fluid, although the antimicrobial activity against Listeria monocytogenes declined during storage. This study showed the behaviour of P. pentosaceus SB83 in glycerol and in simulated vaginal fluid. However, it is necessary to optimise the formulation to produce an actively probiotic vaginal gel.

Evaluation of characteristics ofPediococcusspp. to be used as a vaginal probiotic

The aim of our research was to select, identify and characterize an isolate of lactic acid bacteria to be considered as a vaginal probiotic. Thirty-five isolates of Pediococcus spp. showed bacteriocinogenic activity against Listeria monocytogenes and the ability to survive in simulated vaginal fluid (SVF) at pH 4.2. One isolate of Pediococcus spp. was selected and characterized to evaluate its safety before the use as vaginal probiotic. Pediococcus pentosaceus SB83 did not show the presence of virulence factors such as the production of gelatinase, lipase and DNase, haemolytic activity, nor the presence of virulence genes (genes esp, agg, gelE, efaAfm, efaAfs, cylA, cylB and cylM). Pediococcus pentosaceus SB83 was considered sensitive to chloramphenicol, gentamicin, streptomycin, kanamycin, erythromycin and ampicillin. This strain was considered resistant to tetracycline and vancomycin. Pediococcus pentosaceus SB83 was a biofilm producer at different pH values (4.2, 5.5 and 6.5) in SVF and in de Man, Rogosa and Sharpe medium. The in vitro results provide a basis for the use of P. pentosaceus SB83 as a vaginal probiotic, to prevent colonization by L. monocytogenes in pregnant women. The application of vaginal probiotics could have the potential for preventing vaginal infections and consequently reduce abortion and neonatal infections.