Growth Of Foodborne Pathogenic Bacteria Research Articles

Purification, characterization, and identification of a novel bacteriocin produced by Lacticaseibacillus casei KLS1, and its antimicrobial mechanism against Staphylococcus aureus

Staphylococcus aureus (S. aureus) and its biofilm were recognized as one of the major threats to food safety and human health. Bacteriocins produced by Lacticaseibacillus species have been demonstrated to inhibit the growth of foodborne pathogenic bacteria and their biofilm formation. Herein, a novel bacteriocin KLS1 from Lacticaseibacillus casei KLS1 was extracted by ethyl acetate and purified using an AKTA Pure 25 protein chromatography purification system. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses revealed that the molecular mass of bacteriocin KLSI was 3786.91 Da and the amino acid sequence was DTSASIASNKSETNDLLKQIEAANTEVINLNKQID. Bacteriocin KLS1 was stable at pH 2.0∼6.0, sensitive to proteases, and showed excellent thermal stability. Furthermore, bacteriocin KLS1 exhibited broad-spectrum antimicrobial activity against both Gram-positive and Gram-negative bacteria, even fungi. The crystal violet staining assay indicated that bacteriocin KLS1 significantly reduced the relative percentage of S. aureus biofilm (P < 0.05). Meanwhile, bacteriocin KLS1 was found to significantly decrease the metabolic activity of S. aureus by Cell Counting Kit-8 assay (P < 0.05). In addition, scanning electron microscopy and confocal laser scanning microscope showed that bacteriocin KLS1 disrupted the structure of S. aureus biofilm and cell membrane integrity, leading to cell deformation and leakage of contents. These results suggested that bacteriocin KLS1 might have the potential to serve as a biological preservative in the food industry.

Physicochemical, microbial, and sensory characteristics of yogurt with Persian shallot (Allium hirtifolium Boiss) and probiotic bacteria.

The aim of this study was to investigate the characteristics of yogurt prepared with the addition of Persian shallot and probiotic bacteria. The effect of Persian shallot on the viability of probiotic bacteria (Lactobacillus acidophilus and Bifidobacterium bifidum) was evaluated. Furthermore, the antimicrobial effects of shallot and probiotic bacteria on Listeria monocytogenes and Escherichia coli species were investigated. The experiments were performed on days 0, 1, 7, 14, and 21. The results showed that the survival of lactic acid bacteria increased significantly in the presence of shallots (p < .05). The addition of two different probiotic bacteria to the yogurt samples inhibited the pathogenic bacteria. While E. coli bacteria had a 3-log reduction, L. monocytogenes did not grow at all in the presence of probiotic bacteria and shallots. Based on these experiments, it was concluded that the addition of shallots not only increased the survival of probiotic bacteria but also reduced the growth of food-borne pathogenic bacteria. In addition, the addition of probiotic bacteria increased the acceptance of sensory properties of yogurt samples.

Evaluation of bioactive low‐density polyethylene (LDPE) nanocomposite films in combined treatment with irradiation on strawberry shelf‐life extension

A low-density polyethylene (LDPE) film reinforced with cellulose nanocrystals (CNCs) with an encapsulated bioactive formulation (cinnamon essential oil+silver nanoparticles) was developed for preservation of fresh strawberries. Antimicrobial activity of the active LDPE films was tested against Escherichia coli O157:H7, Salmonella typhimurium, Aspergillus niger, and Penicillium chrysogenum by agar volatilization assay. The optimal condition of the films showed ≥75% inhibitory capacity against the tested microbes. Strawberries were stored with different types of films: Group 1 (control): (LDPE+CNCs+Glycerol), Group 2: (LDPE+CNCs+Glycerol+AGPPH silver nanoparticles), Group 3: (LDPE+CNCs+Glycerol+cinnamon), Group 4: (LDPE+CNCs+Glycerol+active formulation), and Group 5: (LDPE+CNCs+Glycerol+active formulation+0.5kGy γ-radiation) at 4°C for 12 days. Weight loss (WL) (%), decay (%), firmness (N), color, and total phenolics and anthocyanin content of the strawberries were measured. Results showed that the most effective LDPE-nanocomposite film for reducing the microbial growth was LDPE+CNCs+Glycerol+active formulation film (Group 4). When combined with γ-irradiation (0.5kGy), the LDPE+CNCs+Glycerol+active formulation (Group 5) significantly reduced both decay and WL by 94%, as compared to the control samples after 12 days of storage. Total phenols (from 952 to 1711mg/kg) and anthocyanin content (from 185 to 287mg/kg) increased with storage time under the different treatments. The mechanical properties, water vapor permeability (WVP), and surface color of the films were also tested. Though the WVP of the films were not influenced by the types of antimicrobial agents, they did significantly (p≤0.05) change color and mechanical properties of the films. Therefore, combined treatment of active film and γ-irradiation has potential as an alternative method for extending the shelf-life of storage strawberries while maintaining fruit quality. PRACTICAL APPLICATION: Bioactive Low-density polyethylene (LDPE) nanocomposite film was developed in the study by incorporating active formulation (essential oil and silver nanoparticle) to extend the shelf life of stored strawberries. The bioactive LDPE-based nanocomposite film along with γ-irradiation could be used to preserve fruits for long-term storage by controlling the growth of foodborne pathogenic bacteria and spoilage fungi.

Analysis of Industrial Bacillus Species as Potential Probiotics for Dietary Supplements.

So far, Bacillus species bacteria are being used as bacteria concentrates, supplementing cleaning preparations in order to reduce odor and expel pathogenic bacteria. Here, we discuss the potential of Bacillus species as 'natural' probiotics and evaluate their microbiological characteristics. An industrially used microbiological concentrates and their components of mixed Bacillus species cultures were tested, which may be a promising bacteria source for food probiotic preparation for supplementary diet. In this study, antagonistic activities and probiotic potential of Bacillus species, derived from an industrial microbiological concentrate, were demonstrated. The cell free supernatants (CFS) from Bacillus licheniformis mostly inhibited the growth of foodborne pathogenic bacteria, such as Escherichia coli O157:H7 ATCC 35150, Salmonella Enteritidis KCCM 12021, and Staphylococcus aureus KCCM 11335, while some of Bacillus strains showed synergistic effect with foodborne pathogenic bacteria. Moreover, Bacillus strains identified by the MALDI TOF-MS method were found sensitive to chloramphenicol, kanamycin, and rifampicin. B. licheniformis and B. cereus displayed the least sensitivity to the other tested antibiotics, such as ampicillin, ampicillin and sulfbactam, streptomycin, and oxacillin and bacitracin. Furthermore, some of the bacterial species detected extended their growth range from the mesophilic to moderately thermophilic range, up to 54 °C. Thus, their potential sensitivity to thermophilic TP-84 bacteriophage, infecting thermophilic Bacilli, was tested for the purpose of isolation a new bacterial host for engineered bionanoparticles construction. We reason that the natural environmental microflora of non-pathogenic Bacillus species, especially B. licheniformis, can become a present probiotic remedy for many contemporary issues related to gastrointestinal tract health, especially for individuals under metabolic strain or for the increasingly growing group of lactose-intolerant people.

토마토 농가 환경에서 분리한 Bacillus cereus의 열저항성 분석

Bacillus cereus (B. cereus) is a spore forming bacteria with a highly adhesive ability on the food surface and which expresses concern about commercial sterilization due to heat resistance. In this study, the heat challenge was performed at 60℃ for 60 min to derive the importance of the inactivation of bacteria by time during heating 14 isolates of B. cereus from the tomato farm environment. As a result, the final cell counts of B. cereus reduced after heating were –3.6 Log CFU/mL on average (minimum: –2.8 Log CFU/mL, maximum: –4.7 Log CFU/mL). Reduced cell counts of B. cereus after heating for 60 min ranged from 0.5 Log CFU/mL to 2.4 Log CFU/mL. Remained B. cereus after heating can recover in an appropriate environment, and cause foodborne illness. B. cereus existed in the farm environment during the cultivation stage of agricultural products can be transferred to agricultural products through various routes such as soil, toilet handles and worker gloves, thus, the management of B. cereus in a farm environment is essential. In addition, improper sterilization, manufacturing, processing and packaging in the food processing stage cannot be expected to inhibit the complete growth of foodborne pathogenic bacteria, and the risk of foodborne illness can be increased. Therefore, thorough management of these processes is considered important.

티베트 요거트에서 분리한 유산균의 병원성 세균 항균 효과 연구

Yogurt is produced by bacterial fermentation of milk and contains lactic acid bacteria (LAB), which produce various metabolites such as organic acid, hydrogen peroxide, and bacteriocin. This study aimed to investigate cell-free supernatants (CFS) of LAB isolated from Tibetan yogurt. CFS (TY1, TY2, TY3, TY4, TY5, TY6, and TY7) from selected strains of LAB were co-incubated with four different foodborne pathogenic bacteria, namely E. coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus. Inhibition of foodborne pathogenic bacterial growth was not affected in the presence of CFS (pH 6.5). In contrast, CFS without neutralization completely inhibited the growth of the bacteria. Furthermore, when the concentration of CFS (without neutralization) was changed to 1:4 and 1:8, a difference in inhibition was observed between Gram-positive and Gram-negative bacteria. CFS more effectively inhibited the growth of Gram-negative E. coli O157:H7 and S. Typhimurium than Gram-positive L. monocytogenes and S. aureus. These results suggest that organic acids in LAB may inhibit the growth of foodborne pathogenic bacteria, particularly Gram-negative bacteria.

Anti-Parasitic Activity of Cherry Tomato Peel Powders.

Trichomoniasis in humans, caused by the protozoal parasite Trichomonas vaginalis, is the most common non-viral sexually transmitted disease, while Tritrichomonas foetus causes trichomonosis, an infection of the gastrointestinal tract and diarrhea in farm animals and domesticated cats. As part of an effort to determine the inhibitory effects of plant-based extracts and pure compounds, seven commercially available cherry tomato varieties were hand-peeled, freeze-dried, and pounded into powders. The anti-trichomonad inhibitory activities of these peel powders at 0.02% concentration determined using an in vitro cell assay varied widely from 0.0% to 66.7% against T. vaginalis G3 (human); from 0.9% to 66.8% for T. foetus C1 (feline); and from 0.0% to 81.3% for T. foetus D1 (bovine). The organic Solanum lycopersicum var. cerasiforme (D) peels were the most active against all three trichomonads, inhibiting 52.2% (G3), 66.8% (C1), and 81.3% (D1). Additional assays showed that none of the powders inhibited the growth of foodborne pathogenic bacteria, pathogenic fungi, or non-pathogenic lactobacilli. Tomato peel and pomace powders with high content of described biologically active compounds could serve as functional food and feed additives that might help overcome adverse effects of wide-ranging diseases and complement the treatment of parasites with the anti-trichomonad drug metronidazole.

Antibacterial Activity of Clove Oil against Foodborne Pathogenic Bacteria and Sensory Attributes in Clove Oil-Enriched Dairy Products: A Preliminary Study

This study was conducted to evaluate the antibacterial activity against Cronobacter sakazakii and Salmonella enteritidis as well as the sensory attributes of milk products supplemented with various concentrations (control, 0.5%, 1.0%, 1.5%, and 2.0%) of clove oil. In this study, clove oil was shown to have strong antibacterial activities. In addition, all the samples were assessed by ten researchers trained in five sensory attributes, namely, taste, flavor, color, texture, and overall acceptability. Compared to the control, 5% clove oil supplemented was the best in market milk, while in yogurt and kefir, 1.0% supplementation was the best. In terms of sensory attributes, the low score of color and flavor of market milk, yogurt, and kefir is attributed to the characteristics of the supplemented clove oil. Consequently, this study presents the possibility of producing bio-functional milk products supplemented with clove oil, and for controlling the growth of foodborne pathogenic bacteria in milk products using clove oil.

유산균을 이용한 유청 바이오컨버전 산물의 병원성 세균 항생물막 효과

Whey is a major by-product of cheese manufacture and contains many valuable constituents, such as β-lactoglobulin, lactoferrin and immunoglobulin. The current study determined the anti-biofilm activity of bioconversion of whey by Lactobacillus plantarum (LP-W), L. rhamnosus GG (LR-W), L. brevis (LB-W) and Enterococcus faecium (EF-W) against foodborne pathogenic bacteria, Escherichia coli O157:H7 and Listeria monocytogenes. When the foodborne pathogenic bacteria were co-incubated with LP-W, LR-W, LB-W or EF-W, biofilms by E. coli O157:H7 and L. monocytogenes were significantly reduced by all bioconversion of whey. Moreover, LP-W, LR-W, LB-W and EF-W also dramatically reduced pre-formed biofilm by E. coli O157:H7 and L. monocytogenes, suggesting that the bioconversion of whey effectively suppress the development and disruption of biofilm by foodborne pathogenic bacteria. Furthermore, in order to determine the growth kinetics of E. coli O157 and L. monocytogenes planktonic cells in the presence the bioconversion of whey, LP-W, LR-W, LB-W and EF-W did not significantly inhibited the growth of foodborne pathogenic bacteria, implying that the bioconversion of whey reduces the biofilm without the decrease of bacterial growth. Taken together, these results suggest that bioconversion of whey by lactic acid bacteria could be a promising agent for the reduction of microbial biofilm.

Characterization of Weissella confusa DD_A7 isolated from kimchi

Foodborne pathogenic bacteria like, Escherichia coli 0157:H7, Bacillus cereus and Salmonella typhimurium are the biggest threat to food industries. Their growth in the environment and transmission of deadly diseases has become a challenge. The present study confirmed the genetic identity of DD_A7 is similar to the reported probiotic strains of Weissella confusa by analyzing the polymorphism in the conserved region of 16S-rRNA sequence. The Kimchi isolated, non-pathogenic W. confusa DD_A7 strain has shown the potential to control the growth of foodborne pathogens. Furthermore, the cell-free culture supernatant of DD_A7 shows the potential to rapture the membrane integrity of E. coli 0157:H7 by influencing the Ca++ ion channels. The safety concern associated with the usage of DD_A7 strain was also determined by testing its antibiotic susceptibility against different antibiotics and confirmed its non-toxic behavior on mammalian cells. Nevertheless, the strain has also encompassed several applications such as isolation of amylolytic and proteolytic enzymes. Collectively, the study will help to control the growth of foodborne pathogenic bacteria using the studied probiotic strain. In addition, the study will also help to construct a species-specific probe in future for the identification of the non-pathogenic strain of W. confusa for its application in food industries.

Antagonistic Activities and Probiotic Potential of Lactic Acid Bacteria Derived From a Plant-Based Fermented Food.

In this study, antagonistic activities and probiotic potential of lactic acid bacteria (LAB) derived from a plant-based fermented food, kimchi, were demonstrated. The cell free supernatants (CFS) from Lactobacillus curvatus KCCM 43119, Leuconostoc mesenteroides KCCM 43060, Weissella cibaria KCTC 3746, and W. koreensis KCCM 41517 completely inhibited the growth of foodborne pathogenic bacteria, while neutralized CFS (pH 6.5) partially inhibited the growth. The competition, exclusion, and displacement of foodborne pathogenic bacteria by the LAB strains from adhesion to HT-29 cells were investigated. The LAB strains were able to compete with, exclude, and displace the foodborne pathogenic bacteria. However, the degree of inhibition due to the adhesion was found to be a LAB strain-dependent phenomenon. The LAB strains showed high coaggregation with foodborne pathogenic bacteria, and they also exhibited high resistance to acidic condition. Except W. cibaria KCTC 3746, all LAB strains were capable of surviving in the presence of bile salts. Furthermore, while all LAB strains were resistant to chloramphenicol, kanamycin, streptomycin, gentamicin, and erythromycin, only W. cibaria KCTC 3746 and W. koreensis KCCM 41517 displayed resistance to vancomycin. These results suggest that the LAB strains derived from kimchi exerted antagonistic activities against foodborne pathogenic bacteria with probiotic potential.

Viability of and Escherichia coli O157:H7 and Listeria monocytogenes in a delicatessen appetizer (yogurt-based) salad as affected by citrus extract (Citrox©) and storage temperature

The antimicrobial effect of citrus extract (at 1 mL/kg [C1] and 2 mL/kg [C2]) on naturally occurring microbiota and inoculated pathogens (E. coli O157:H7 and L. monocytogenes at ca. 6 log cfu/g) in the traditional Greek yogurt-based salad Tzatziki stored at 4, 10, or 21 °C, was examined. Lactic acid bacteria (LAB) were high (8.0–8.5 log cfu/g) and varied only minimally for both the control (untreated) and the citrus extract-treated salad samples, whereas the higher citrus extract concentration yielded the lowest yeast populations, irrespective of temperature, during the entire storage period. Populations of inoculated E. coli (6 log cfu/g) declined in both untreated and citrus extract-treated samples from day 0–70, 35, and 15 at 4, 10, and 21 °C, respectively. Citrus extract had a significant effect on the survival of the inoculated E. coli O157:H7, with reductions of 2.8–4.8 log cfu/g in the citrus extract-treated samples at the end of the storage period. Our data show that L. monocytogenes survived in both untreated and citrus extract-treated samples during the entire storage period, irrespective of the storage temperature. The higher concentration of citrus extract had a significant effect on the survival of L. monocytogenes in the treated samples, and reductions of 1.5–3.0 logs were noted on final day 70, 35 and 15 at 4, 10 and 21 °C, respectively. The results of our study demonstrated the potential of citrus extract as a natural compound that can control the growth of food-borne pathogenic bacteria, such as E. coli O157:H7 and L. monocytogenes in Tzatziki, a yogurt-based salad.

Inhibitory Effects of Gallic Acid Isolated from Caesalpinia mimosoides Lamk on Cholangiocarcinoma Cell Lines and Foodborne Pathogenic Bacteria.

Gallic acid was isolated from Caesalpinia mimosoides Lamk and the structure s identified based on spectroscopic analysis and comparison with authentic compound. In this study we compared the ability of natural gallic acid (nGA) and commercial gallic acid (cGA) to inhibit the proliferation of cholangiocarcinoma cell lines (M213, M214) and foodborne pathogenic bacteria (Salmonella spp. and Plesiomonas shigelloides). Both nGA and cGA had the same inhibitory effects on cell proliferation by inducing apoptosis of cholangiocarcinoma cell lines. In addition, nGA inhibited growth of foodborne pathogenic bacteria in the same manner as cGA. Our results suggest that nGA from Caesalpinia mimosoides Lamk is a potential anticancer and antibacterial compound. However, in vivo studies are needed to elucidate the specific mechanisms involved.

The ability of Schisandra chinensis fruit to inhibit the growth of foodborne pathogenic bacteria and the viability and heat resistance of Bacillus cereus spores

SummaryThe objective of this study was to investigate the influence of Schisandra chinensis fruit on the growth of spoilage and pathogenic bacteria and on the viability and heat resistance of Bacillus cereus spores. Schisandra chinensis fruit was extracted with one of three different solvents (50% ethanol, 100% ethanol and distilled water), and the extracts exhibited antimicrobial activity against all the bacteria tested. Particularly, the ethanol extracts of S. chinensis fruit had the strongest activity, in a concentration‐dependent manner. Fractionation of extracts by ion chromatography revealed that the antimicrobial activity of S. chinensis fruit is mainly due to organic acids such as citric acid and malic acid. Meanwhile, S. chinensis fruit extract (10%) significantly reduced the viability and heat resistance of B. cereus spores. Therefore, this study suggests that S. chinensis fruit extract has potential as a natural food preservative and/or sanitising agent for the reduction of spoilage and pathogenic contamination.

Comparison of Oxygen‐ and Nitrogen‐Enriched Atmospheres on the Growth of Listeria Monocytogenes Inoculated on Poultry Breast Fillets

AbstractThe growth behavior of Listeria monocytogenes in the presence of typical spoilage microorganisms on poultry breast fillets (Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, Lactobacillus spp., total viable count) was investigated. The aim of the study was to compare the growth of L. monocytogenes under oxygen‐ and nitrogen‐enriched atmospheres and to figure out possible interactions between L. monocytogenes and typical spoilage microorganisms on skinless poultry breast fillets. Therefore, the natural meat surface was inoculated with L. monocytogenes and packed under two commonly used gas atmospheres (70% O2/30% CO2 and 70% N2/30% CO2). The atmosphere was monitored over the storage period and typical sensory attributes (color, odor, texture, drip loss and general appearance) were evaluated. The results show that the storage under 70% N2/30% CO2 favored the growth of L. monocytogenes in comparison with the 70% O2/30% CO2. Under nitrogen, L. monocytogenes reached a maximal bacterial count of 5.7 (log10 cfu/g) after approximately 500 h of storage, but no specific microorganism could be identified responsible for the favored growth. The growth of L. monocytogenes was suppressed in the oxygen‐enriched atmosphere, whereas B. thermosphacta dominated the spoilage flora. The results indicate that the combination of high oxygen with carbon dioxide and possible interactions with the spoilage background flora cause a delay of the L. monocytogenes growth under 70% O2/30% CO2.Practical ApplicationsFresh poultry meat has become an increasingly popular food during the last 10 years due to its beneficial nutritional composition. From the microbiological point of view, raw poultry meat is sensitive for microbial growth because of its physical and chemical properties. In this context, the prediction of the growth of foodborne pathogenic bacteria e.g., Listeria monocytogenes is of vital importance to ensure a safe poultry production. Therefore, packaging under modified atmosphere conditions is widely established to improve the quality, shelf life as well as safety aspects. Taking into account that the growth of L. monocytogenes is also influenced by the natural spoilage flora of poultry reflects that interactions between the microorganisms have to be considered while packaging poultry filets under modified atmosphere conditions. The present study shows how two commonly used gas mixtures for poultry influence the outgrowth of L. monocytogenes in the presence of the natural background flora.

Antibacterial activity of pectic-based edible films incorporated with Mexican lime essential oil

Edible films have been used as carriers of foods additives such as antioxidant or antimicrobial agents. Lime essential oil has demonstrated to act as an antimicrobial agent on food systems which can be incorporated into a film matrix. In this research edible films were prepared with two different raw matters, lime bagasse pectic extract and lime pomace pectic extract at 0.70, 0.85 and 1.00% pectin equivalents. Mexican lime essential oil was incorporated to a film-forming solution at 0, 500 and 1000 mg L−1 and 0.70% glycerol was added as plasticizer. Edible films antibacterial activity against food-borne pathogenic bacteria (Escherichia coli O157:H7, Salmonella Typhimurium, Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes) was investigated by the disc diffusion method, with zones of inhibition measured after 24 h of incubation. The higher inhibition zone was against E. coli (20.6 ± 1.17 mm). Edible films prepared with pectic extracts (Mexican Lime bagasse and pomace) presented higher inhibition against Gram negative bacteria, but those prepared with bagasse pectic extract were more effective against all five bacteria studied. Pectic extracts edible films incorporated with Mexican lime essential oil inhibited the growth of foodborne pathogenic bacteria and can be useful in the preservation of food to increase shelf life.

Anti-listerial synergism of leaf essential oil of Metasequoia glyptostroboides with nisin in whole, low and skim milks

ObjectiveTo examine the individual and synergistic anti-listerial effect of nisin and leaf essential oil of Metasequoia glyptostroboides (M. glyptostroboides) against one of the leading foodborne pathogens Listeria monocytogenes (L. monocytogenes) ATCC 19116 in milk samples. MethodsThe whole (8%), low (1%) and skim (no fat content) milk samples were inoculated with L. monocytogenes ATCC 19116 along with leaf essential oil of M. glyptostroboides or nisin alone as well in combinations. ResultsIn this study, the leaf essential oil at the concentrations of 2% and 5% revealed strong anti-listerial effect against L. monocytogenes ATCC 19116 in all categories of milk samples. Nisin at the concentrations of 250 and 500 IU/mL displayed a strong inhibitory effect against ATCC 19116 as compared to the control group. Additionally, synergistic combinations of leaf essential oil (1%) and nisin (62.5, 125, 250 and 500 IU/mL) also had a remarkable anti-listerial synergism in all the tested milk samples including whole, low and skim milk after 14 days. ConclusionsAs a major finding, the leaf essential oil of M. glyptostroboides might be a useful candidate for using in food industry to control the growth of foodborne pathogenic bacteria as confirmed by its potent anti-listerial synergistic effect with nisin against L. monocytogenes ATCC 19116 in different milk samples.

Characterization and purification of a new bacteriocin with a broad inhibitory spectrum produced byLactobacillus plantarumlp 31 strain isolated from dry-fermented sausage

Characterization and purification of a new bacteriocin produced by Lactobacillus plantarum LP 31 strain, isolated from Argentinian dry-fermented sausage. Lactobacillus plantarum LP 31 strain produces an antimicrobial compound that inhibits the growth of food-borne pathogenic bacteria. It was inactivated by proteolytic enzymes, was stable to heat and catalase and exhibited maximum activity in the pH range from 5.0 to 6.0. Consequently, it was characterized as a bacteriocin. It was purified by RP (reverse-phase) solid-phase extraction, gel filtration chromatography and RP-HPLC. Plantaricin produced by Lact. plantarum LP 31 is a peptide with a molecular weight of 1558.85 Da as determined by Maldi-Tof mass spectrometry and contains 14 amino acid residues. It was shown to have a bactericidal effect against Pseudomonas sp., Staphylococcus aureus, Bacillus cereus and Listeria monocytogenes. The bacteriocin produced by Lact. plantarum LP 31 may be considered as a new plantaricin according to its low molecular weight and particular amino acid composition. In view of the interesting inhibitory spectrum of this bacteriocin and because of its good technological properties (resistance to heat and activity at acidic pH), this bacteriocin has potential applications as a biopreservative to prevent the growth of food-borne pathogens and food spoilage bacteria in certain food products.

Inhibitory Effect of Melastoma candidum D. Don Acetone Extract on Foodborne Pathogenic Bacteria Survival in Food Products

Melastoma candidum D. Don, a Taiwanese folk medicinal plant, has high levels of antibacterial and bactericidal activity. Our aim was to determine whether and to what extent an acetone extract of this plant inhibits the growth of foodborne pathogenic bacteria. M. candidum acetone extract had marked inhibitory effect on test bacteria introduced into sliced pork, which was then stored at 4°C. At the end of storage (day 12), the bacterial concentrations dropped by 1.59 to 2.91 log CFU/g compared with the control. In steamed rice stored at 30°C, a 0.2% extract decreased initial (before storage) concentrations of Bacillus cereus from 2.01 log CFU/g to an undetectable level, which remained for at least 24 h. After 72 to 168 h of storage, test bacterial concentrations were reduced by 2.59 to 5.66 log CFU/g. In fresh noodles stored at 30°C, both initial and final bacterial concentrations were decreased. At the end of storage (72 to 168 h), test bacteria concentrations were reduced by 1.85 to 2.88 log CFU/g. Overall, M. candidum acetone extract had an inhibitory effect on foodborne pathogenic bacteria in different food model systems.

Effect of Chaff Vinegar on the Growth of Food-Borne Pathogenic Bacteria

The growth inhibitiory effect of chaff vinegar against various food-borne pathogenic bacteria was evaluated. Bacterial growth was evaluated in chaff vinegar at concentrations of 15, 30, 50, 65, 80, and 100% using the paper disc diffusion method and 0.5, 1.0, 1.5, 1.8, 2.0, 2.2 and 2.5% in broth. In the paper disc diffusion assay, chaff vinegar showed a clear zone on both the Gram-positive bacteria; Listeria monocytogenes, Staphylococcus aureus and Gram-negative bacteria; Escherichia coli O157:H7, Salmonella Typhimurium, and Vibrio parahaemolyticus. Chaff vinegar exhibited the greatest growth inhibition for V. parahaemolyticus. The bactericidal effect of chaff vinegar on the E. coli O157:H7 was tested at concentrations ranging from 0.5 to 2.5% (v/v) in the LB broth media. Chaff vinegar retarded the lag phase time of the growth curve in proportion in a concentration-dependent manner. Chaff vinegar at 2.5% completely inhibited the growth of E. coli O157:H7.