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ABSTRACT: The purpose of this study is to determine the survival and nisin production behaviors of two strains of Lactococcus lactis under different stress conditions that represent the food ecosystem. In this respect, the survival ratios of two nisin producers
were determined under different pH, temperature, NaCl, and bile salt concentrations. Then, nisin production levels of the
strains were determined at each stress conditions. Both strains had similar growth or inactivation patterns under the same
stress conditions. NaCl and bile salt stresses on the survival ratio of the strains could be successfully described by the
exponential decay function, whereas Gaussian function produced good fits for temperature and pH stresses. The nisin activity
of two nisin producers (in their mid-exponential and/or early stationary phase) decreased dramatically under all stress conditions,
except osmotic (NaCl) and low temperature applications. The results of this study showed that two nisin producers had similar
adaptive responses under severe stress conditions, which could be described by appropriate mathematical equations. Moreover,
the effect of harsh environment on the nisin activity of L. lactis strains depends on the stress factors applied.
Applied Biochemistry and Biotechnology 04/2012; 158(2):387-397. · 1.94 Impact Factor
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ABSTRACT: Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed
that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45,
and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation
with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer.
Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded
the loss of nisin in the late phase of the fermentation.
Journal of Industrial Microbiology and Biotechnology 04/2012; 36(4):481-490. · 2.73 Impact Factor
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ABSTRACT: Nisin production in continuous cultures of bioengineered Lactococcus lactis strains that incorporate additional immunity and regulation genes was studied. Highest nisin activities were observed at
0.2h–1 dilution rate and 12.5g l–1 fructose concentration for all strains. Recombinant strains were able to produce greater amounts of nisin at dilution rates
below 0.3h−1 compared to the control strain. However, this significant difference disappeared at dilution rates of 0.4 and 0.5h–1. For the strains LL27, LAC338, LAC339, and LAC340, optimum conditions for nisin production were determined to be at 0.29,
0.26, 0.27, and 0.27h–1 dilution rates and 11.95, 12.01, 11.63, and 12.50gl–1 fructose concentrations, respectively. The highest nisin productivity, 496IUml–1h–1, was achieved with LAC339. The results of this study suggest that low dilution rates stabilize the high specific nisin productivity
of the bioengineered strains in continuous fermentation. Moreover, response surface methodology analysis showed that regulation
genes yielded high nisin productivity at wide ranges of dilution rates and fructose concentrations.
Journal of Industrial Microbiology and Biotechnology 04/2012; 36(6):863-871. · 2.73 Impact Factor
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[show abstract]
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ABSTRACT: Nisin production in continuous cultures of bioengineered Lactococcus lactis strains that incorporate additional immunity and regulation genes was studied. Highest nisin activities were observed at 0.2 h(-1) dilution rate and 12.5 g l(-1) fructose concentration for all strains. Recombinant strains were able to produce greater amounts of nisin at dilution rates below 0.3 h(-1) compared to the control strain. However, this significant difference disappeared at dilution rates of 0.4 and 0.5 h(-1). For the strains LL27, LAC338, LAC339, and LAC340, optimum conditions for nisin production were determined to be at 0.29, 0.26, 0.27, and 0.27 h(-1) dilution rates and 11.95, 12.01, 11.63, and 12.50 g l(-1) fructose concentrations, respectively. The highest nisin productivity, 496 IU ml(-1) h(-1), was achieved with LAC339. The results of this study suggest that low dilution rates stabilize the high specific nisin productivity of the bioengineered strains in continuous fermentation. Moreover, response surface methodology analysis showed that regulation genes yielded high nisin productivity at wide ranges of dilution rates and fructose concentrations.
Journal of Industrial Microbiology 05/2009; 36(6):863-71. · 1.80 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45, and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer. Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded the loss of nisin in the late phase of the fermentation.
Journal of Industrial Microbiology 02/2009; 36(4):481-90. · 1.80 Impact Factor
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ABSTRACT: Mutational analyses revealed the 21.5 kb plasmid-encoded lactose fermentation and proteolytic activity properties in Lactococcus lactis ssp. lactis MN24. Reductions in maximum specific growth rate and population density of the 21.5 kb plasmid-cured mutant of MN24 confirmed the data obtained by mutation tests. Plasmid curing, polymerase chain reaction and DNA sequence analyses data showed that the lacticin 481 operon was located on 22.4 kb plasmid. The phage resistance system in strain MN24 was identified as an adsorption inhibition type and chromosomally encoded via phage–host interaction tests and mutation analyses.
International Journal of Dairy Technology 01/2009; 62(1):118 - 125. · 1.11 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The purpose of this study is to determine the survival and nisin production behaviors of two strains of Lactococcus lactis under different stress conditions that represent the food ecosystem. In this respect, the survival ratios of two nisin producers were determined under different pH, temperature, NaCl, and bile salt concentrations. Then, nisin production levels of the strains were determined at each stress conditions. Both strains had similar growth or inactivation patterns under the same stress conditions. NaCl and bile salt stresses on the survival ratio of the strains could be successfully described by the exponential decay function, whereas Gaussian function produced good fits for temperature and pH stresses. The nisin activity of two nisin producers (in their mid-exponential and/or early stationary phase) decreased dramatically under all stress conditions, except osmotic (NaCl) and low temperature applications. The results of this study showed that two nisin producers had similar adaptive responses under severe stress conditions, which could be described by appropriate mathematical equations. Moreover, the effect of harsh environment on the nisin activity of L. lactis strains depends on the stress factors applied.
Applied biochemistry and biotechnology 10/2008; 158(2):387-97. · 1.94 Impact Factor
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ABSTRACT: The plasmid stability of three wild type Lactococcus lactis strains and their mutants was investigated at different incubation time and temperatures in two different media [M17 broth and reconstituted skim milk (RSM)]. The results showed that both incubation times and temperature are effective on plasmid loss. The plasmid profiles of wild type strains exhibited 8 to 9 distinct plasmid species with molecular weights from 2.1 to 24.0 kb. Lactose fermentation ability was found to be encoded by 22.2 (strain U70), 23.6 (strain U29) and 24.0 (strain U52) kb plasmids in the wild type strains, respectively. The stabilities of the plasmids were explained by applying a second-order polynomial modeling system. Reasonable fittings were obtained for the model and the adjusted regression coefficients (R ( 2 ) (adj)) were between 0.76 and 0.99 for the overall data. Overall, it was found that incubation time had the most profound effect on plasmid stability, with plasmid loss occurring after 72 h, while temperatures in the range of 15-40 degrees C also induced plasmid instability.
Journal of Industrial Microbiology and Biotechnology 12/2007; 34(11):729-37. · 2.73 Impact Factor
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ABSTRACT: MisL is a Salmonella enterica serotype Typhimurium fibronectin binding protein whose expression is induced during infection of mice. T-POP transposon mutagenesis identified marT as a positive regulatory element controlling expression of a misL::lacZYA transcriptional fusion. Gel shift analysis identified MarT as a transcriptional activator of the misL promoter.
Journal of Bacteriology 06/2007; 189(10):3922-6. · 3.83 Impact Factor
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ABSTRACT: This work presents the isolation and partial characterization of a new lactococcal bacteriocin produced by Lactococcus lactis ssp. lactis MC38. The bacteriocin demonstrated broad spectrum of inhibition activity against both pathogenic and food spoilage organisms, and various lactic acid bacteria. This antimicrobial substance appeared to be proteinaceous because its activity was completely inactivated by proteinase K and α-chymotrypsin. It was heat and pH stable. The apparent molecular mass of the purified bacteriocin, determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, was 8.0 kDa. The amino acid composition of the studied bacteriocin was found to be quite different from known lactococcal bacteriocins. The calculation of the number of amino acid residues in the bacteriocin molecule revealed that it contained 62 amino acids.
Journal of Food Safety. 01/2007; 27(1):17 - 29.
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ABSTRACT: A massive neutrophil influx in the intestine is the histopathological hallmark of Salmonella enterica serovar Typhimurium-induced enterocolitis in humans. Two major hypotheses on the mechanism leading to neutrophil infiltration in the intestinal mucosa have emerged. One hypothesis suggests that S. enterica serovar Typhimurium takes an active role in triggering this host response by injecting proteins, termed effectors, into the host cell cytosol which induce a proinflammatory gene expression profile in the intestinal epithelium. The second hypothesis suggests a more passive role for the pathogen by proposing that bacterial invasion stimulates the innate pathways of inflammation because the pathogen-associated molecular patterns of S. enterica serovar Typhimurium are recognized by pathogen recognition receptors on cells in the lamina propria. A review of the current literature reveals that, while pathogen recognition receptors are clearly involved in eliciting neutrophil influx during S. enterica serovar Typhimurium infection, a direct contribution of effectors in triggering proinflammatory host cell responses cannot currently be ruled out.
FEMS Immunology & Medical Microbiology 05/2006; 46(3):320-9. · 2.44 Impact Factor
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ABSTRACT: In this study, bacteriocins from two Lactococcus lactis subsp. lactis isolates from raw milk samples in Turkey designated OC1 and OC2, respectively, were characterized and identified. The activity spectra of the bacteriocins were determined by using different indicator bacteria including Listeria, Bacillus and Staphylococcus spp. Bacteriocins were tested for their sensitivity to different enzymes, heat treatments and pH values. Loss of bacteriocin activities after alpha-amylase treatment suggested that they form aggregates with carbohydrates. Molecular masses of the purified bacteriocins were determined by SDS-PAGE. PCR amplification was carried out with specific primers for the detection of their structural genes. As a result of these studies, the two bacteriocins were characterized as nisin and lacticin 481, respectively. Examination of plasmid contents of the isolates and the results of plasmid curing and conjugation experiments showed that in L. lactis subsp. lactis OC1 strain the 39.7-kb plasmid is responsible for nisin production, lactose fermentation and proteolytic activity, whereas the 16.0-kb plasmid is responsible for lacticin 481 production and lactose fermentation in L. lactis subsp. lactis OC2 strain.
Molecular Nutrition & Food Research 04/2006; 50(3):306-13. · 4.30 Impact Factor
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Infection and Immunity 02/2006; 74(1):19-27. · 4.16 Impact Factor
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Cagla Tükel,
Manuela Raffatellu,
Andrea D Humphries,
R Paul Wilson,
Helene L Andrews-Polymenis,
Tamara Gull,
Josely F Figueiredo,
Michelle H Wong,
Kathrin S Michelsen, Mustafa Akçelik,
L Garry Adams,
Andreas J Bäumler
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ABSTRACT: Knowledge about the origin and identity of the microbial products recognized by the innate immune system is important for understanding the pathogenesis of inflammatory diseases. We investigated the potential role of Salmonella enterica serotype Typhimurium fimbriae as pathogen-associated molecular patterns (PAMPs) that may stimulate innate pathways of inflammation. We screened a panel of 11 mutants, each carrying a deletion of a different fimbrial operon, for their enteropathogenicity using the calf model of human gastroenteritis. One mutant (csgBA) was attenuated in its ability to elicit fluid accumulation and GROalpha mRNA expression in bovine ligated ileal loops. The mechanism by which thin curled fimbriae encoded by the csg genes contribute to inflammation was further investigated using tissue culture. The S. Typhimurium csgBA mutant induced significantly less IL-8 production than the wild type in human macrophage-like cells. Purified thin curled fimbriae induced IL-8 expression in human embryonic kidney (HEK293) cells transfected with Toll-like receptor (TLR) 2/CD14 but not in cells transfected with TLR5, TLR4/MD2/CD14 or TLR11. Fusion proteins between the major fimbrial subunit of thin curled fimbriae (CsgA) and glutathione-S-transferase (GST) elicited IL-8 production in HEK293 cells transfected with TLR2/CD14. Proteinase K treatment abrogated IL-8 production elicited in these cells by GST-CsgA, but not by synthetic lipoprotein. GST-CsgA elicited more IL-6 production than GST in bone marrow-derived macrophages from TLR2+/+ mice, while there was no difference in IL-6 secretion between GST-CsgA and GST in macrophages from TLR2-/- mice. These data suggested that CsgA is a PAMP that is recognized by TLR2.
Molecular Microbiology 11/2005; 58(1):289-304. · 5.01 Impact Factor
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ABSTRACT: Lactococcus lactis subsp. lactis strains isolated from traditional fermented milk products in Turkey were used to determine their phage resistance against three different lactic phages. The following modes of action were examined: phage adsorption inhibition in five strains, abortive infection (heat sensitive phage resistance) in three strains, restriction/modification in four strains and blocking of phage DNA injection in one strain. The genetic nature of the phage resistance systems in these strains was determined by comparison of phage proliferation parameters, e.g. adsorption (%), EOP, burst size, latent period and production of major capsid protein, between wild-type strains and their plasmid-cured derivatives.
International Journal of Food Science & Technology 12/2001; 35(5):473 - 481. · 1.26 Impact Factor
