Indicator Strains Research Articles

Characterization and Antimicrobial Studies of Iturin-Like and Bogorol-Like Lipopeptides From Brevibacillus spp. Strains GI9 and SKDU10.

Accession numbers for whole-genome sequence of Brevibacillus sp. strain GI9 and SKDU10 are CAGD01000001 to CAGD01000061 and LSSO00000000, respectively. Members of the genus Brevibacillus have been demonstrated to produce a variety of bioactive compounds including polyketides, lipopeptides and bacteriocins. Lipopeptides are non-ribosomally synthesized surface-active compounds with antimicrobial, antitumor, and immune-stimulatory activities. They usually exhibit strong antifungal and antibacterial activities and are considered as promising compounds in controlling fungal diseases. In this study, we have characterized two lipopeptides from Brevibacillus sp. strains GI9 and SKDU10. The corresponding lipopeptides were purified by reverse-phase high-performance liquid chromatography. Mass analysis and characterization by MALDI-TOF-MS (Matrix-assisted laser desorption ionization time-of-flight mass spectrometry) analysis revealed production of an iturin-like lipopeptide by strain GI9 and bogorol-like lipopeptide by strain SKDU10. Both lipopeptides exhibited broad spectrum antibacterial activity and inhibited the growth of various fungi. They showed minimum inhibitory concentration (MIC) values between 90 and 300 μg/ml against indicator strains of bacteria and drug-resistant Candida indicator strains. The lipopeptides did not show phytotoxic effect in seed germination experiments but caused hemolysis. Further, both lipopeptides inhibited the growth of fungi on fruits and vegetables in in vitro experiments, thereby exhibited potential use in biotechnological industry as effective biocontrol agents.

Antibacterial Activity of Mangrove Root Extracts from Ngurah Rai Mangrove Forest, Denpasar-Bali

The increasing rate of antimicrobial resistance in the past decades has motivated the search for novel antibacterial compounds to overcome infectious diseases. Among diverse natural sources, mangrove ecosystems offer untapped sources of biological active compounds for future antibacterial medicine. This research was aimed to evaluate antibacterial activities of crude extracts of four dominant mangrove plants from the Ngurah Rai Mangrove Forest namely Rhizophora mucronata, Avicennia marina, Rhizophora apiculata, and Sonneratia alba. Roots of these four plants were extracted using methanol, chloroform, and n-hexane. These crude extracts were tested against two Gram positive bacteria (Staphylococcus aureus and Streptococcus mutans) and two Gram negative bacteria (Escherichia coli dan Klebsiella pneumoniae) by disc difussion assay. We found that 3 mg/mL of N-hexane crude extracts from R. apiculata yielded the highest zone of inhibition of 8.64 mm against S. aureus. While, 3 mg/mL of chloroform crude extract of R. apiculata yielded the highest inhibition of 19.83 mm against S. mutans. Unfortunately, no zone of inhibition was observed when crude extracts were tested against Gram negative indicator strains. Our results indicate that the root crude extracts of R. apiculata yielded the highest zone of inhibition against Gram positive indicator strains compared to root crude extracts of R. mucronata, S. alba, and A. marina. Further research is required to determine the antibacterial activities of the mangrove crude extracts against other bacterial indicator strains to determine their spectrum of activities.

Evaluation of the rCIM for carbapenemase detection in Enterobacterales and Pseudomonas aeruginosa and description of the TSBrCIM, an optimized variant

ObjectivesThe rapid Carbapenem Inactivation Method (rCIM) was evaluated with a strain collection of 164 and 69 carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa, respectively, that produced various carbapenemases. For an improved carbapenemase detection in Enterobacterales, an optimized variant of the rCIM named TSBrCIM was developed. MethodsBacterial isolates were incubated with two meropenem disks in distilled water (rCIM) or tryptic soy broth (TSBrCIM). After centrifugation, the supernatant was incubated with a susceptible E. coli indicator strain in tryptic soy broth. Growth of the indicator strain implied carbapenemase activity in the test strain. ResultsThe rCIM detected 100/113 carbapenemase-producing Enterobacterales, resulting in a sensitivity of 88.5% and a specificity of 94.1%. For P. aeruginosa, sensitivity and specificity were 96.0% and 100%, respectively. The TSBrCIM was able to detect 105/113 carbapenemase-producing Enterobacterales, resulting in a sensitivity of 92.9% and a specificity of 96.1%. ConclusionThis study shows that the TSBrCIM can be valuable tool for detection of carbapenemases in Enterobacterales in the clinical laboratory, while the rCIM showed the best results for carbapenemase detection in P. aeruginosa.

THE EFFECT OF BACTERIOCIN ENTEROCOCCUS ITALICUS ONU 547 AND ESSENTIAL OILS ON THE GROWTH OF OPPORTUNISTIC MICROORGANISMS

Purpose. To evaluate the effectiveness of bacteriocin of Enterococcus italicusONU 547 and essential oils individually and in combination against indicatorstrains of opportunistic pathogens. Methods. The antagonistic activity of essential oils and bacteriocin was determined by the optical density of the bacterial suspension of test strains (Salmonella enterica NCTC 6017, Escherichia coli АТСС 25922, Pseudomonas aeruginosa АТСС 27853, Pseudomonas putida KT 2440, Enterococcus faecalis АТСС 29212, Klebsiella pneumoniae АТСС 10031,Staphylococcus aureus АТСС 25923). The index of fractional inhibitory activity(FIC) was calculated by adding the FIC values of bacteriocin E. italicus ONU 547and the studied essential oils. The results. The maximum antimicrobial effect was caused by the essential oils of Anisum officinalis and Melissa officinalis, which suppressed the growth of test strains more than 50.0%. When using bacteriocin of E. italicus ONU 547 suppression of viability of indicator strains did not exceed 30.0%. Experimental combinations of essential oils and bacteriocin caused 4 types of consequences: synergy effect; additive effect; antagonistic effect; interactiveeffect (no interaction effect). In most cases, the combined action of bacteriocinand essential oils caused an additive effect. Conclusions. This study demonstrated the potential of using different combinations of natural antimicrobial compounds. The obtained results provide grounds for further development and optimization ofcombinations of essential oils and probiotic strains of microorganisms for use in food and pharmaceutical biotechnology.

The Influence of Environmental Conditions on the Antagonistic Activity of Lactic Acid Bacteria Isolated from Fermented Meat Products.

The aim of this study was to determine the impact of environmental conditions on the antimicrobial properties of 21 lactic acid bacteria strains in the selected indicator bacteria. To assess the antimicrobial activity of the whole bacteria culture (WBC), the agar well diffusion method was used. The interference of LAB strains with the growth of the selected indicator bacteria was evaluated by incubating co-cultures in the food matrix. Based on the conducted research, it was found that environmental conditions have a significant impact on the antimicrobial activity of lactic acid bacteria strains. The highest antimicrobial activity was recorded under optimal conditions for the development of LAB, the incubation time being different depending on the indicator strain used. The tested LAB strains were characterized by a high ability to inhibit indicator strains, especially in the food matrix. These results led us to further characterize and purify the antimicrobial compound produced by lactic acid bacteria taking into account changing environmental conditions.

Pool water disinfection by ozone-bromine treatment: Assessing the disinfectant efficacy and the occurrence and in vitro toxicity of brominated disinfection by-products

Pool water is continuously circulated and reused after an extensive treatment including disinfection by chlorination, ozonation or UV treatment. In Germany, these methods are regulated by DIN standard 19643. Recently, the DIN standard has been extended by a new disinfection method using hypobromous acid as disinfectant formed by introducing ozone into water with naturally or artificially high bromide content during water treatment.In this study, we tested the disinfection efficacy of the ozone-bromine treatment in comparison to hypochlorous acid in a flow-through test rig using the bacterial indicator strains Escherichia coli, Enterococcus faecium, Pseudomonas aeruginosa, and Staphylococcus aureus and the viral indicators phage MS2 and phage PRD1. Furthermore, the formation of disinfection by-products and their potential toxic effects were investigated in eight pool water samples using different disinfection methods including the ozone-bromine treatment. Our results show that the efficacy of hypobromous acid, depending on its concentration and the tested organism, is comparable to that of hypochlorous acid. Hypobromous acid was effective against five of six tested indicator organisms. However, using Pseudomonas aeruginosa and drinking water as test water, both tested disinfectants (0.6 mg L−1 as Cl2 hypobromous acid as well as 0.3 mg L−1 as Cl2 hypochlorous acid) did not achieve a reduction of four log10 levels within 30 s, as required by DIN 19643.The formation of brominated disinfection by-products depends primarily on the bromide concentration of the filling water, with the treatment method having a smaller effect. The eight pool water samples did not show critical values in vitro for acute cytotoxicity or genotoxicity in the applied assays. In real pool water samples, the acute toxicological potential was not higher than for conventional disinfection methods. However, for a final assessment of toxicity, all single substance toxicities of known DBPs present in pool water treated by the ozone-bromine treatment have to be analyzed additionally.

An efficient method to screen for the soil bacteria producing therapeutically effective antibiotics.

The discovery of novel therapeutic antimicrobials has become an urgent issue in response to the global crisis of the spread of multi-drug-resistant bacteria. In this report, we propose an efficient screening method for antimicrobial agents with therapeutic potential from soil bacteria. With this method, colonies of the soil bacteria were formed first on agar plates containing only an extract of soil, followed by an overlay of soft agar containing the pathogens, an antibiotic target. Then, we selected the colonies that formed the inhibitory zones on soft agar and evaluated the therapeutic efficacy of their culture supernatants using a silkworm bacterial infection model. Using Staphylococcus aureus as an indicator strain to obtain bacteria that produce therapeutically effective antimicrobials, we succeeded in reducing the screening size by 20-fold compared to the conventional method. An analysis of 86 antibiotics producers identified in this study indicated that the majority belonged to Streptomyces sp. and Lysobacter sp., well-known producers of secondary metabolites. Besides, the presence of eight genera and 37 species among the identified species indicated the diversity of antibiotic producers. Based on the finding of our study, we propose this method as an efficient way to discover novel antimicrobial agents that are therapeutically effective.

Antibacterial and antifungal activities of hydroalcoholic hands products sold in Côte d’Ivoire during covid-19

In the midst of the COVID-19 pandemic, hydroalcoholic products are widely used for hand disinfection. Côte d'Ivoire has also opted for this barrier measure. Ivorian markets and supermarkets have been filled with new hydroalcoholic products of various compositions and colors, certified or not by the Ivorian standardization agency. It was important to verify the antimicrobial efficacy of these hydroalcoholic products. To do this, we tested 16 hydroalcoholic products collected from supermarkets in Abidjan. The microbial load on the hands of 144 volunteers was determined before and after hand rubbing. These hydroalcoholic products were also tested for antibacterial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia and Proteus mirabilis; and antifungal activity against Aspergillus fumigatus and Penicillium chrysogenum. The results of this study showed that hydroalcoholic products tested significantly reduced the microbial load on the hands after friction. The germ inhibition rate was between 94.99 and 99.97%. Of the 16 hydroalcoholic products, only 3 showed antibacterial and antifungal activity on all indicator strains. In contrast, 4 showed no antibacterial and antifungal activity on these strains. The low efficacy of hydroalcoholic products tested in vitro is an indicator of the lack of quality control of these products. Some of them could not therefore guarantee the health security of the populations.

Paeonol Attenuates Quorum-Sensing Regulated Virulence and Biofilm Formation in Pseudomonas aeruginosa.

With the prevalence of multidrug-resistant bacteria and clinical -acquired pathogenic infections, the development of quorum-sensing (QS) interfering agents is one of the most potential strategies to combat bacterial infections and antibiotic resistance. Chinese herbal medicines constitute a valuable bank of resources for the identification of QS inhibitors. Accordingly, in this research, some compounds were tested for QS inhibition using indicator strains. Paeonol is a phenolic compound, which can effectively reduce the production of violacein without affecting its growth in Chromobacterium violaceum ATCC 12472, indicating its excellent anti-QS activity. This study assessed the anti-biofilm activity of paeonol against Gram-negative pathogens and investigated the effect of paeonol on QS-regulated virulence factors in Pseudomonas aeruginosa. A Caenorhabditis elegans infection model was used to explore the anti-infection ability of paeonol in vivo. Paeonol exhibited an effective anti-biofilm activity against Gram-negative bacteria. The ability of paeonol to interfere with the AHL-mediated quorum sensing systems of P. aeruginosa was determined, found that it could attenuate biofilm formation, and synthesis of pyocyanin, protease, elastase, motility, and AHL signaling molecule in a concentration- and time-dependent manner. Moreover, paeonol could significantly downregulate the transcription level of the QS-related genes of P. aeruginosa including lasI/R, rhlI/R, pqs/mvfR, as well as mediated its virulence factors, lasA, lasB, rhlA, rhlC, phzA, phzM, phzH, and phzS. In vivo studies revealed that paeonol could reduce the pathogenicity of P. aeruginosa and enhance the survival rate of C. elegans, showing a moderate protective effect on C. elegans. Collectively, these findings suggest that paeonol attenuates bacterial virulence and infection of P. aeruginosa and that further research elucidating the anti-QS mechanism of this compound in vivo is warranted.

Purification and Characterization of a New Halocin HA4 from Haloferax larsenii HA4 Isolated from a Salt Lake.

Halocins are antimicrobial peptides secreted by different members of haloarchaea. Halocin HA4 was purified from Haloferax larsenii HA4 using combination of ultrafiltration and chromatographic techniques. It was found to be ~ 14kDa with unique N-terminal sequence, H2N-AEEEIFXPDX, which did not show homology with the known sequence suggesting a new/novel compound. It was found to be heat resistant up to 100°C, stable at pH 2.0-10.0, and retained complete activity in the presence of different organic compounds such as methanol, ethanol, acetone, isopropanol, ethyl acetate, Tween 80, acetonitrile, SDS, Triton X-100, and urea. However, complete activity was reduced after the treatment with trypsin, papain, and proteinase K suggesting proteinaceous nature of the compound. The cytocidal nature of halocin HA4 was evidenced with complete loss of viable count of indicator strain, H. larsenii HA10. The change in FTIR spectrum of halocin-treated cells suggested halocin HA4 interacts with cell membrane and nucleic acids of the target cells. Thus, we report a new halocin inhibitory to related strains and may be applied in the preservation of salted foods and leather hides in the respective industries.

Antimicrobial Activity and Functional Genes of Actinobacteria from Coastal Wetland.

Isolation of culturable actinobacteria from coastal wetlands and screening of their potential biological activities are important for the development of new marine natural products. We collected and isolated 109 actinobacteria from the Sanggou Bay and the Swan Lake wetlands, in the coast of Weihai, China. Of the 109 isolates, 104 had antimicrobial activity against at least one indicator strain. The 35 strains with the strongest inhibitory effects were chosen for the screening of the biosynthesis gene clusters of polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS). Four strains with the PKS gene, six strains with the NRPS gene, and three strains with both genes were detected. Eight of the 13 strains with PKS or NRPS genes belong to the genera Streptomyces, and other strains belonged to genus Micromonospora, Nocardiopsis, Rhodococcus, Saccharomonospora, and Staphylococcus. Our results reveal that the culturable actinobacteria isolated from coastal wetlands showed broad-spectrum antimicrobial activities, and some strains with antimicrobial activities possessed PKS and NRPS genes. Thus, culturable actinobacteria from coastal wetlands may contain potential new bioactive substances.

Novel Strategy for the Development of Antibacterial TiO2 Thin Film onto Polymer Substrate at Room Temperature.

This work demonstrates a novel method to deposit an antibacterial TiO2 thin film on a polymer substrate at room temperature. A combination of sol–gel and photon assistance was used in the experiment in order to avoid any thermal processes of thin film crystallization. The morphological photograph of samples indicated that the TiO2 thin film was perfectly coated on the PVC substrate without any cracks or pinholes. Chemical analysis by EDS and XPS reported that the thin film consisted of titanium (Ti), oxygen (O), and carbon (C). The Raman spectrum proved that the thin film was the anatase phase of TiO2 and, furthermore, that it was contaminated with carbon remaining from the photon assistance process. In addition, the optical band gap of the thin film was 3.35 eV, suggesting that the photocatalytic activity of TiO2 should occur under UV-A radiation. The bacteria viability assay was examined using E. coli and S. typhimurium as indicator strains under UV-A irradiation (365 nm) at different times. The data from OD and CFU count revealed that >97% of bacteria were killed after 60 min of irradiation, and the bacteria were completely killed at 120 min for E. coli and 180 min for S. typhimurium.

Genome mining of a marine-derived Streptomyces sp. PDH23 isolated from sponge in Da Nang sea for secondary metabolite gene clusters

The streptomyces is one of the best characterized ubiquitous filamentous bacteria from the actinobacteriaclass. They are known to produce thousands of specialized metabolite biosynthesis gene clusters (SMBG). Their SMBG clusters have multiple activities ranging from antimicrobial, antitumor, antiviral and probiotic. Streptomyces strain and their isolates with interesting biological activities against gram-positive and gram-negative indicator strains was recently characterised. Currently, they are employed in more than half of all antibiotics used in human and veterinary medicine. With the increase in drug resistance bacteria, it is important to mine for new natural chemicals.In this study, screening via disk-diffusion agar method revealed that Streptomyces sp. PDH23 isolated from the Rhabdastrellaglobostellata marine sponge sample from Da Nang, Vietnam produce antimicrobial agents with a wide spectrum of activities. This species can produce highly active enzymes, which breakdown celluloses, amyloses and proteins. On top of that they are shown to restrict the grow of the gram positive Bacillus cereus ATCC14579 (BC), Staphylococcus aureus ATCC25923 (SA), the gram-negativeVibrio parahaemolyticus ATCC17802 (VP) and the Candida albicans ATCC10231 fungus (CA). They are antimethicillin-resistant S. aureus(MRSA) ATCC33591 andmethicillin-resistantS. epidermidis (MRSE) ATCC35984. The taxonomy of PDH23 was characterized using 16S rRNA analysis. Whole genome sequencing of PDH23 showed 8594820 base pairs with GC content of 72.03%. Mining of secondary metabolites reveals gene clusters responsible for the biosynthesis of known and/or novel secondary metabolites, including different types of terpene, NRPS-like , PKS, PKS-like, hglE-KS, betalactone, melanin, t1pks, t2pks, t3pks, nrps, indole, siderophore, bacteriocin, ectoine, butyrolactone, phenazine.

Lactic Acid Bacterium With Antimicrobial Properties From Selected Malay Traditional Fermented Foods

Traditional or local fermented foods have been the favourite sources for Lactic acid bacteria (LAB) used for starter cultures. Traditional food such as fermented cassava ‘tapai ubi’, fermented glutinous rice ‘tapai pulut’ and fermented shrimp paste ‘belacan’ have been local heritage consumed as Malay delicacies. In this work, 33 LAB samples were isolated from tapai ubi, tapai pulut and belacan and out of these only 5 LAB isolates (PG, PH, BG, UG and UL) showed inhibitory properties against selected indicator organisms (Bacillus subtilis, Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus). Morphologically, isolate PG, PH, BG are cocci, UL is rod and UG is coccobacillus. Biochemically, isolates (PG, PH, BG UL and UG) are found to be Gram positive, non motile, lactose fermenter and catalase negative. The 16s Ribosomal RNA gene sequencing was carried out and each was identified with an accession number (PB: MT645488, PH: MT645489; BG: MT645490 UG: MT645491 and UL MT645492). Isolates PG and PH from tapai pulut belonged to Pediococcus pentosaceus (at 99% and 98%, respectively). Meanwhile, isolate from Belacan BG belonged to Enterococcus faecium (99%), and those from fermented shrimp, UG and UL belonged to Weissella confusa (99%), and Lactobacillus fermentum (98%), respectively. Majority of the isolates demonstrated broad spectrum inhibition against both Gram positive and negative indicator strains. Compared to the rest of isolates, PH exhibited the highest antibacterial activity against Bacillus subtilis. These results suggested that isolate PH are the most potent isolates which is producing antimicrobial agent with potential as food preservatives.

Antimicrobial properties of Lactobacillus cell‐free supernatants against multidrug‐resistant urogenital pathogens

The healthy vaginal microbiota is dominated by Lactobacillus spp., which provide an important critical line of defense against pathogens, as well as giving beneficial effects to the host. We characterized L. gasseri 1A‐TV, L. fermentum 18A‐TV, and L. crispatus 35A‐TV, from the vaginal microbiota of healthy premenopausal women, for their potential probiotic activities. The antimicrobial effects of the 3 strains and their combination against clinical urogenital bacteria were evaluated together with the activities of their metabolites produced by cell‐free supernatants (CFSs). Their beneficial properties in terms of ability to interfere with vaginal pathogens (co‐aggregation, adhesion to HeLa cells, biofilm formation) and antimicrobial activity mediated by CFSs were assessed against multidrug urogenital pathogens (S. agalactiae, E. coli, KPC‐producing K. pneumoniae, S. aureus, E. faecium VRE, E. faecalis, P. aeruginosa, P. mirabilis, P. vulgaris, C. albicans, C. glabrata). The Lactobacilli tested exhibited an extraordinary ability to interfere and co‐aggregate with urogenital pathogens, except for Candida spp., as well as to adhere to HeLa cells and to produce biofilm in the Lactobacillus combination. Lactobacillus CFSs and their combination revealed a strong bactericidal effect on the multidrug resistant indicator strains tested, except for E. faecium and E. faecalis. The antimicrobial activity was maintained after heat treatment but decreased after enzymatic treatment. All Lactobacilli showed lactic dehydrogenase activity and production of D‐ and L‐lactic acid isomers on Lactobacillus CFSs, while only 1A‐TV and 35A‐TV released hydrogen peroxide and carried helveticin J and acidocin A bacteriocins. These results suggest that they can be employed as a new vaginal probiotic formulation and bio‐therapeutic preparation against urogenital infections. Further, in vivo studies are needed to evaluate human health benefits in clinical situations.

Diversity and characterization of temperate bacteriophages induced in Pasteurella multocida from different host species

BackgroundBacteriophages play important roles in the evolution of bacteria and in the emergence of new pathogenic strains by mediating the horizontal transfer of virulence genes. Pasteurella multocida is responsible for different disease syndromes in a wide range of domesticated animal species. However, very little is known about the influence of bacteriophages on disease pathogenesis in this species.ResultsTemperate bacteriophage diversity was assessed in 47 P. multocida isolates of avian (9), bovine (8), ovine (10) and porcine (20) origin. Induction of phage particles with mitomycin C identified a diverse range of morphological types representing both Siphoviridae and Myoviridae family-types in 29 isolates. Phage of both morphological types were identified in three isolates indicating that a single bacterial host may harbour multiple prophages. DNA was isolated from bacteriophages recovered from 18 P. multocida isolates and its characterization by restriction endonuclease (RE) analysis identified 10 different RE types. Phage of identical RE types were identified in certain closely-related strains but phage having different RE types were present in other closely-related isolates suggesting possible recent acquisition. The host range of the induced phage particles was explored using plaque assay but only 11 (38%) phage lysates produced signs of infection in a panel of indicator strains comprising all 47 isolates. Notably, the majority (9/11) of phage lysates which caused infection originated from two groups of phylogenetically unrelated ovine and porcine strains that uniquely possessed the toxA gene.ConclusionsPasteurella multocida possesses a wide range of Siphoviridae- and Myoviridae-type bacteriophages which likely play key roles in the evolution and virulence of this pathogen.

Biopreservative Action of Bacteriocin from Pediococcus pentosaceus on the Microbial Load of Apple Juice

Abstract: Aim: The aim of the study is to explore the bio preservative role of Pediococcus pentosaceus. Background: Bacteriocins are proteinaceous or peptidic in nature produced by lactic acid bacteria and generally recognized as safe (GRAS). It ranges from 2 to 200kDa in molecular weight. It inhibits the growth of similar or closely related bacterial strains. Materials and Methods: In this experiment, “Appam batter” has been taken as our sample, collected from Vellore city. The sample was fermented for seven and fourteen days simultaneously from which 1mL of the samples were taken and inoculated in 100mL of production media consist of 3% skim milk. The bacteria were allowed to grow for 24 hrs and serially diluted and spread plate was done on MRS agar plate. Seventeen bacterial strains were isolated. The preliminary assays were carried out to identify the bacteria as Lactobacillus species, such as Gram staining and catalase. All the strains were screened for bacteriocin by agar well diffusion assay. The strains which showed zone of inhibition was further subjected to antibacterial activity. Results: The isolated strains were found to show a clear zone of inhibition against Listeria monocytogenes MTCC 5260 used as the indicator strain. Further the isolated strains were tested for antimicrobial activity against certain food borne pathogens which includes Staphylococcus aureus MTCC 5257, Salmonella typhi MTCC2501, Escherichia coli MTCC 2089 and Pseudomonas aeruginosa MTCC 2242. The isolated strain VITAB01 showed a broad spectrum activity against all the pathogens with a highest zone of inhibition of 13mm, 12800(AU/mg) and thus subjected to 16srRNA molecular level analysis and found out to be Pediococcus pentosaceus MH134499. The isolate upon characterization showed to be heat stable at 60°C and optimum pH 6. On purification it has a specific activity of 325.20(AU/ mg) with a final yield of 3.12. The molecular weight of the bacteriocin was found to be 17kDa. Conclusion: The supernatant was mixed with apple juice and checked for its bio preservative effect. Decrease in colonies was found to be 26.82%. Key words: Appam batter, Lactic Acid Bacteria, Purification, Bacteriocin, Apple juice, Preservative.

Biopreservation of pineapple wine using immobilized and freeze dried microcapsules of bacteriocin producing L. plantarum.

Bacteriocin producing L. plantarum (ATCC 8014) was immobilized (MC) and freeze dried (FD) to conduct preliminary study on its potential in biopreservation of pineapple wine. Cell survival in both simulated gastric and intestinal juice was significantly better for MC and FD than free cells (FC).The antimicrobial activity and bacteriocin production of L. plantarum was detected against L. acidophilus, A. aceti, S. cerevisiae, E. coli, S. aureus and B. subtilis as indicator strains. Bacteriocin activity from MC revealed high zone of inhibition as compared to FC. In wine, bacteriocin found effective at 3.5 pH. Significant decrease of total soluble solids and sugar observed in wine treated with MC and FC. FD and MC treated wine was organolepticaly more accepted as compared to FC however, there was no significant difference in overall acceptability of pineapple wine under all treatments at P < 0.05.

Veratraldehyde as a food additive produced by the marine isolate Streptomyces diastaticus LC360811

Twelve actinomycete isolates were derived from 6 sediment samples collected from the Red Sea coast, Egypt. The marine isolate, RS10, the most potent candidate, proved its capability to produce antimicrobial compound(s) that strongly inhibit both Gram-positive and Gram-negative bacteria. RS10 was identified by 16S rRNA gene sequencing as Streptomyces diastaticus LC360811. Culture supernatant of S. diastaticus LC360811 was extracted using n-butanol and tested against bacterial indicator strains using the disc diffusion method. The crude extract was partially purified using column chromatography and assessed for antimicrobial activity. Fraction no. 35 showed the highest antimicrobial activity against Acinatobacter sp. (34 mm), Pseudomonas aeruginosa ATCC 9027 (30 mm), Candida albicans (26 mm), Staphylococcus aureus ATCC 47077 (25 mm), Aeromonas hydrophila (23 mm),Streptococcus iniae (22 mm)and Borditella sp. (18 mm). This active fraction was then identified as veratraldehyde using spectroscopic techniques: GC-MS-MS and HPLC (diode array detector) and compared with the authentic reference. Veratraldehyde as a natural preservative proved to be a good candidate to preserve the flavor of juice, yogurt, and fermented milk and was able to control the growth of bacterial pathogens compared to the non-treated products till day fourteen.

Growth and adhesion inhibition of pathogenic bacteria by live and heat-killed food-origin Lactobacillus strains or their supernatants.

The study aimed to evaluate qualitatively and quantitatively the antimicrobial capacity of 10 potential probiotic Lactobacillus strains against model enteropathogens and spoilage microorganisms. The probiotic strains (live and heat-killed forms) were also assessed for their ability to inhibit adhesion of selected pathogens to Caco-2 cells. The largest inhibition zones (the diffusion method) were connected with the usage of whole bacteria cultures (WBC), also high and moderate with cell-free supernatant (CFS) and the lowest with cell-free neutralized supernatant (CNS). The highest antagonistic activity of Lactobacillus strains was observed against L. monocytogenes strains, moderate activity against Salmonella, Shigella, Escherichia coli, Pseudomonas and, the lowest against S.aureus, Bacillus and Enterococcus. The inhibition of adhesion to Caco-2 cells was very high in the case of E. coli, Salmonella and L. monocytogenes, and moderate in the case of S.aureus. On average, the inhibition effect was higher when pathogenic bacteria were treated by WBC, than heat-killed Lactobacillus. Although, in most samples, the effect was not significantly different (P> 0.05). The strains Lb. brevis O24 and Lb. rhamnosus K3 showed the biggest overall antimicrobial properties, and were most effective in adherence inhibition of investigated indicator strains. These bacteria or their metabolites can be used for the production of various foods or pharmaceutical products.