• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.389-397
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• 2002

Bacteriocin-producing lactic acid bacteria were isolated from kimchi. One isolate producing the most efficient bacteriocin was identified and named Lactococcus lactis B2, based on the biochemical properties and 16S rDNA sequences. The B2 bacteriocin inhibited many different Gram positive bacteria including Lactococcus, Lactobacillus, Leuconostoc, Enterococcus, Streptococcus, and Staphylococcus, but did not inhibit Gram-negative bacteria. The bacteriocin was maximally produced at temperatures between $25^{\circ}C\;and\;30^{\circ}C$ and at the initial pH of 7.0. Ninety $\%$ of the activity remained after 10 min of heat treatment at $121^{\circ}C,\;and\;100\%$, after 1 h exposure to organic solvents. The bacteriocin was purified from culture supernatant by ammonium sulfate precipitation, CM Sepharose column chromatography, ultrafiltration, and finally, by reverse-phase HPLC. A 1.58-kb fragment was amplified from B2 chromosome by using a primer set designed from the published nisA sequence. Sequencing result showed that the fragment contained the whole nisZ and 5' portion of nisB, whose gene product was involved in postmodification of nisin. The upstream sequence, however, was completely different from those of reported nisin genes.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.619-623
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• 1991

To investigate nisin production and resistance of Lactococcus lactis ssp. tactis ML (L. lactis $ML_8$, effects of medium, pH of culture broth, and cell growth on the nisin activity, and effect of nisin with or without $Ca^[2+}$ ion on the growth of L. lactzs were analyzed. In the bio-assay of nisin by the agar diffusion method, inhibition-zone diameter of Micrococcus Javus was propotional to the logarithm of nisin concentration ranged 0.5~20 unitlml (12.5~500 ng/mf). Nisin activity of the pasteurized culture filtrates of L. lactis MLs was high at pH 2!3 but was inactivated completely at pH over 6.0. Nisin production of the L. lactis $ML_8$ cultured on LTB broth increased at late logarithmic phase and reached 10.5 unitlml after 16 hr. The cell growth of L. lactis LM 0230, a plasmid free and nisin sensitive strain, was inhibited on agar medium containing 7 unitlrnl of nisin, while L. lactis $ML_8$ showed high survival ability at 20 unitld of nisin. When 40 mM $Ca^[2+}$ ion was added to Elliker broth with 8 unitlml of nisin, the growth pattern of L. lactis $ML_8$ was similiar to that on control medium which did not contain nisin and $Ca^[2+}$ ion, and this suggested that $Ca^[2+}$ increased the nisin resistance of the L. lactis.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.53-60
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• 2000

Strain BH5 was isolated from naturally fermented Kimchi and identified as a bacteriocin producer, which has bactericidal activity against Micrococcus flavus ATCC 10240. Strain BH5 was identified tentatively as Lactococcus lactis by the API test and some characteristics. Lactococcus lactis BH5 showed a broad spectrum of activity against most of the non-pathogenic and pathogenic microorganisms tested by the modified deferred method. The activity of lacticin BH5, named tentatively as the bacteriocin produced by Lactococcus lactis BH5, was detected at the mid-log growth phase, reached its maximum during the early stationary phase, and decreased after the late stationary phase. Lacticin BH5 also showed a relatively broad spectrum of activity against non-pathogenic and pathogenic microorganisms as tested by the spot-on-lawn method. Its antimicrobial activity on sensitive indicator cells was completely disappeared by protease XIV or ${\alpha}$-chymotrypsin. The inhibitory activities of lacticin BH5 were detected during treatments up to 100$^{\circ}C$ for 30 min. Lacticin BH5 was very stable over a pH range of 2.0 to 9.0 and was stable with all the organic solvents examined. The cell concentration and bacteriocin production in strain BH5 were maximum when grown at 30$^{\circ}C$ in a modified MRS medium supplemented with 0.5% tryptone, 1.0% yeast extract, and 0.5% beef extract as nitrogen sources. It demonstrated a typical bactericidal mode of inhibition against Micrococcus flavus ATCC 10240. Lacticin BH5 was purified through ammonium sulfate precipitation, ethanol precipitation, and CM-Sepharose column chromatography. The apparent molecular mass of lacticin BH5 was estimated to be in the region of 3.7 kDa, by the direct detection of bactericidal activity after SDS-PAGE. Mutant strain NO141 which was isolated by nitrosoguanidine mutagenesis produced about 4 fold more bacteriocin than the wild type.

• Microbiology and Biotechnology Letters
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• v.22 no.3
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• pp.240-245
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• 1994

Relation the phage defense mechanism of phage resistant Lactococcus lactis subsp. cremoris ATCC 11602-A1 to its cell wall components was investigated. To determine whether teichoic acid which is known to be one of the phage receptor site present on the cell wall, phage adsorption was examined after treatment 5% TCA(60%$\CIRC $C) and concanavalin A to the cell wall of A1 and parent strain. However, the adsorption rate of two strains did not change. Total amount of phosphate after TCA treatment did not change in both strains, but a difference between the two strains was observed. Ribitol and glycerol, components of teichoic acid, could not be detected in the cell walls of two strains by GC analysis. These results suggest that although teichoic acid was not present in the cell walls of both strains, the composition of cell wall of two strains was not identical. Measurement of amount of protein and SDS-polyacryamide gel electrophoresis were carried out to examine the involvement of cell wall protein in phage resistance, showing that protein is nothing to do with phage adsorption of parent strain, but phage resistance of A1 is related to protein. Cell wall carbohydrates of A1 contained rhamnose, glucose, and galactose. Total amount of carbohydrate of 1% SDS-treated A1 cell wall was reduced to the level of parent strain. The results suggest that phage resistance of A1 was due to the presence of a higher level of carbohydrates then parent strain, and to interaction of carbohydrate and protein.

• Food Science of Animal Resources
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• v.28 no.4
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• pp.457-462
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• 2008

Lactococcus lactis NK34, isolated from jeotgal (Korean traditional fermented fish), produces bacteriocin against bovine mastitis pathogens such as Staphylococcus aureus 7, S. aureus 8, Staphylococcus chromogenes 10, S. chromogenes 19, Staphylococcus hominis 9, Streptococcus uberis E290, Enterococcus faecium E372, Streptococcus agalactiae ATCC 13813, Pseudonocardia autotrophia KCTC 9455, and Staphylococcus simulans 78. Lacticin NK34 was inactivated by protease XIV but not by protease IX, protease XIII, proteinase K, $\acute{a}$-chymotrypsin, trypsin, and pepsin. Also, lacticin NK34 was stable over a pH range of 2 to 9 for 4 hr and withstood exposure to temperatures of 30-$100^{\circ}C$ for 30 min. Lacticin NK34 showed bactericidal effects against S. simulans 78. This bacteriocin was purified using ammonium sulfate precipitation, ion exchange chromatography, ultrafiltration, and hydrophobic chromatography. Tricin-SDS-PAGE of purified bacteriocin gave the same molecular weight (3.5 kDa) as nisin. The gene encoding this bacteriocin was amplified by PCR using nisin gene-specific primers. It showed similar sequences to this nisin Z gene. These results indicate that lacticin NK34 is a nisin-like bacteriocin, and could be used as an antimicrobial alternative for livestock.

• The Korean Journal of Physiology and Pharmacology
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• v.28 no.2
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• pp.153-164
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• 2024

This study aimed to identify metabolic biomarkers and investigate changes in intestinal microbiota in the feces of healthy participants following administration of Lactococcus lactis GEN-001. GEN-001 is a single-strain L. lactis strain isolated from the gut of a healthy human volunteer. The study was conducted as a parallel, randomized, phase 1, open design trial. Twenty healthy Korean males were divided into five groups according to the GEN-001 dosage and dietary control. Groups A, B, C, and D1 received 1, 3, 6, and 9 GEN-001 capsules (1 × 10¹¹ colony forming units), respectively, without dietary adjustment, whereas group D2 received 9 GEN-001 capsules with dietary adjustment. All groups received a single dose. Fecal samples were collected 2 days before GEN-001 administration to 7 days after for untargeted metabolomics and gut microbial metagenomic analyses; blood samples were collected simultaneously for immunogenicity analysis. Levels of phenylalanine, tyrosine, cholic acid, deoxycholic acid, and tryptophan were significantly increased at 5-6 days after GEN-001 administration when compared with predose levels. Compared with predose, the relative abundance (%) of Parabacteroides and Alistipes significantly decreased, whereas that of Lactobacillus and Lactococcus increased; Lactobacillus and tryptophan levels were negatively correlated. A single administration of GEN-001 shifted the gut microbiota in healthy volunteers to a more balanced state as evidenced by an increased abundance of beneficial bacteria, including Lactobacillus, and higher levels of the metabolites that have immunogenic properties.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.185-191
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• 2000

The water-soluble glucan produced by Lactococcus lactis 1370 affects the formation of dental plaque by Streptococcus mutans. In this study the factors affecting the formation of water-soluble glucan were assessed as the optical density of culture supernatant of Lactococcus lactis 1370 in the spectrophotometer. 1. The optical density of culture supernatant was high when Lactococcus lactis 1370 was cultured in M17 broth with 5% sucrose, while being low in culture supernatant of Streptococcus mutans. 2. The optical density of culture supernatant was higher when Lactococcus lactis 1370 was cultured in M17 broth with 10% sucrose than when being cultured without sucrose (p<0.05), and was higher at pH 7 than pH 5 (p<0.05). 3. The optical density of culture supernatant was the highest at $37^{\circ}C$ among $32^{\circ}C,\;37^{\circ}C\;and\;42^{\circ}C$, and was higher in the anaerobic incubator than in the aerobic incubator (p<0.05). 4. The optical density of culture supernatant was the highest in the media containing 1.0mM $CaCl_2$ (p<0.05), 2.5mM KCl (p<0.05), and 1.6mM $MgCl_2$. 5. When Streptococcus mutans was cultured in the media containing a quarter culture supernatant of Lactococcus lactis 1370 grown in M17 broth, the mean weight of produced artificial plaque was 103.0mg on the wire, whereas being significantly reduced to 5.6mg in the media containing a quarter culture supernatant of Lactococcus lactis 1370 grown in M17 broth containing 5% sucrose (p<0.05). These results indicate that the water-soluble glucan is more formed by Lactococcus lactis 1370 in the media containing sucrose or under the adequate conditions for the growth of bacteria, and inhibits the formation of artificial plaque by Streptococcus mutans.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.333-339
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• 2015

Red lip mullet Chelon haematocheilus (body weight = $468{\pm}91g$) which became sick during an outbreak of disease at mariculture facilities at Cheonsu Bay, Korea, during July-August 2013, were examined to identify the cause of the disease. Diseased mullets displayed green liver syndrome, and Lactococcus garvieae were isolated from their internal organs. Argulus sp., Trichodina sp., and/or Vibrio spp. were also discovered in some infected fish. Histopathological examination revealed that fatty liver syndrome with hepatocyte degeneration, reflected in heterokaryons, inflammatory lesions, and melanomacrophage centers ($MMC_S$), had caused fibrosis around the kidney, spleen, and blood vessels. After the outbreak, visceral fat and green liver syndrome in the mullets were consistently observed throughout the year in the same mariculture facilities, indicating that the cultured mullets suffered a chronic metabolic disorder. Although Vibrio spp. were also isolated from some individuals, L. garvieae, which is known to be a causative agent of red lip mullet mortality, was isolated from all diseased individuals. This is the first report of L. garvieae infection in cultured red lip mullet.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.840-843
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• 2000

The structure of gal/lac operon of Lactococcus lactis ssp. lactis ATCC7962 was partially characterized and the gene (galM) encoding galactose mutarotase was cloned together with the order; galA-galM-galK-galT. The galM was found to be 1,027 bp in length and encoded the protein of 37,609 Da calculated molecular mass. The deduced amino acid sequence showed a homology with GalM proteins from several other microorganisms. Thus, the galM gene was expressed in Escherichia coli and the product was identified as a 38 kDa protein which corresponded to the size estimated from DNA sequence. mutarotase activity of the IPTG inducedrecombinant was 2.7 times increased against that of the host strain.

• Journal of Microbiology and Biotechnology
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• v.16 no.5
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• pp.786-790
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• 2006

Cellular components of Lactococcus lactis ssp. lactis (heat-killed whole cells, cytoplasm, and cell walls) were tested for their in vivo immunopotentiating activity. Peritoneal macrophages from mice orally administered with heat-killed whole cells exhibited significantly greater phagocytic activity than the groups administered with cell-wall fraction or cytoplasm fraction. The cytotoxicity of natural-killer cells was the highest in the group administered with whole cells, and the production of cytokines ($IFN-\gamma$, IL-2, and IL-12) in spleen cells was significantly higher, when cellular components were injected, and it tended to be higher in the cell-wall and cytoplasm groups than in the whole-cell group. Interestingly, the cytokine production of Peyer's patch cells was high, when cytoplasm fractions were administered. These results demonstrate that whole cells and cytoplasm and cell-wall fractions of L. lactis ssp. lactis have immunopotentiating activities, which are related to the stimulation of Peyer's patches.