• 미생물학회지
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• 제54권4호
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• pp.445-447
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• 2018

한국의 전통시장에서 구입한 김치에서 분리된 Leuconostoc lactis CCK940은 sucrose와 maltose를 이용하여 중합도가 4이상인 올리고당을 생산하였다. L. lactis CCK940의 유전체는 1,741,511 bp의 2개 contig로 구성된 염색체로 조합되었으며 G + C의 비율은 43.33%로 나타났다. 염색체 DNA에서 1,698개의 코딩 유전자, 12개의 rRNA, 68개의 tRNA 유전자가 확인되었다. L. lactis CCK940은 올리고당을 생산할 수 있는 sucrose phosphorylase, maltose phosphorylase, ${\beta}$-galactosidase 등의 glucosyltransferase 생합성 유전자들을 지니고 있었다.

• Journal of Microbiology
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• 제41권2호
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• pp.63-72
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• 2003

Chronic inflammatory bowel disease (IBD) such as Crohn's disease or ulcerative colitis, affects around 2 in every 1000 individuals in western countries and its incidence, particularly amongst children, is increasing. IBD shows extreme morbidity with impact on all aspects of quality of life. If left untreated, IBD can lead to death. Conventional treatment of IBD involves powerful immunosuppressive chemotherapies and surgical intervention. Long-term anti-inflammatory medication is required and so patients are often subject to a spectrum of unpleasant side effects. Interleukin-10 (IL-10) is a cytokine that acts to suppress inflammation. When however administered by injection, the high levels of IL-10 that are distributed throughout the body also lead to side effects. Lactococcus lactis can be genetically engineered to secrete biologically active cytokines. When applied to the mucosa, these L. lactis can actively deliver such cytokines. By use of this principle we developed a new therapeutic approach for IBD. Administration of L. lactis that secretes murine IL-10 cures and prevents IBD in mice. The use of the engineered L. lactis gets around the problem of delivering IL-10, allowing dramatic reduction of the effective dose. A sincere concern exists about the possible dangers of uncontrolled, deliberate release of genetically modified microorganisms, such as could occur following application in healthcare. We engaged in the establishment of adequate means for biological growth control of engineered L. lactis by targeted gene exchange between thyA and hIL-10.

• Journal of Microbiology and Biotechnology
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• 제16권2호
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• pp.318-324
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• 2006

In order to develop an oral vaccine to prevent H. pylori infection, we have expressed the hpaA gene of H. pylori K51 isolated from Korean patients, encoding 29-kDa HpaA that is known to be localized on the cell surface and flagella sheath, in a live delivery vector system, Lactococcus lactis. The hpaA gene, amplified by PCR using the genomic DNA of H. pylori K51, was cloned in the pGEX-2T vector, and the DNA sequence analysis revealed that the hpaA gene of H. pylori K51 had 99.7% and 94.8% identity with individual hpaA genes of the H. pylori 26695 strain (U.K) and the J99 strain (U.S.A). A polyclonal anti-HpaA antibody was raised in rats using GST-HpaA fusion protein as the antigen. The hpaA gene was inserted in an E. coli-L. lactis-shuttle vector (pMG36e) to express in L. lactis. Western blot analysis showed that the expression level of HpaA in the L. lactis transformant remained constant from the exponential phase to the stationary phase, without extracelluar secretion. These results indicate that the HpaA of H. pylori K51 was successfully expressed in L. lactis, and suggest that the recombinant L. lactis expressing HpaA may be applicable as an oral vaccine to induce a protective immune response against H. pylori.

• Journal of Microbiology and Biotechnology
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• 제21권2호
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• pp.154-161
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• 2011

L. lactis sk071115 has been shown to grow more actively and generate lower levels of lactate in glucose-defined medium with nitrate than in medium with Mn(IV). By adding Mn(IV) to a L. lactis culture, lactate production was relatively reduced in combination with Mn(II) production, but cell mass production levels did not increase. Both cell-free extract and intact L. lactis cells reacted electrochemically with Mn(IV) but did not react with Mn(II) upon cyclic voltammetry using neutral red (NR) as an electron mediator. A modified graphite felt cathode with NR (NR-cathode) was employed to induce electrochemical reducing equivalence for bacterial metabolism. Cell-free L. lactis extract catalyzed the reduction of Mn(IV) to Mn(II) under both control and electrochemical reduction conditions; however, the levels of Mn(II) generated under electrochemical reduction conditions were approximately 4 times those generated under control conditions. The levels of Mn(II) generated by the catalysis of L. lactis immobilized in the NR-cathode (L-NR-cathode) under electrochemical reduction conditions were more than 4 times that generated under control conditions. Mn(II) production levels were increased by approximately 2.5 and 4.5 times by the addition of citrate to the reactant under control and electrochemical reduction conditions, respectively. The cumulative Mn(II) produced from manganese ore by catalysis of the L-NR-cathode for 30 days reached levels of approximately 3,800 and 16,000 mg/l under control and electrochemical reduction conditions, respectively. In conclusion, the electrochemical reduction reaction generated by the NR-cathode activated the biochemical reduction of Mn(IV) to Mn(II) by L. lactis.

• Journal of Microbiology and Biotechnology
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• 제15권2호
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• pp.330-336
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• 2005

Lactococcus lactis A164 is a nisin Z-producing strain isolated from kimchi. Its antimicrobial spectrum has been found to be active against most Gram-positive bacteria tested, yet inactive against Gram-negative bacteria [3]. Accordingly, to overcome this drawback, the current study attempted to express human $\beta$-defensin-l (hBD-l), which kills both Gram-positive and Gram-negative bacteria in L. lactis AI64. When the hBD-l cDNA was introduced using a nisin Z-controlled expression cassette, the L. lactis A164 transformants grew very poorly, due to the bactericidal effect of the expressed hBD-l against the transformants. Therefore, a gene fusion system was designed to reduce the toxicity of the expressed heterologous protein against the host cells. As such, the hBD-l gene was fused to the DsbC- Tag of pET -40b(+), then introduced to L. lactis A 164. The transformants expressed an intracellular 35.6-kDa DsbC-hBD-l fusion protein that exhibited slight activity against the host cells, yet not enough to strongly inhibit the cell growth. To obtain the recombinant hBD-l, the DsbC-hBD-l fusion protein was purified by nickel-affinity column chromatography, and the DsbC-Tag removed by cleaving with enterokinase. The cleaved mature hBD-l exhibited strong bactericidal activity against E. coli JM109, indicating that the recombinant L. lactis A 164 produced a biologically active hBD-I. In addition, the recombinant L. lactis A 164 was also found to produce the same level of nisin Z as the wild-type.

• Journal of Microbiology and Biotechnology
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• 제31권2호
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• pp.298-303
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• 2021

Comparative genomic analysis was performed on eight species of lactic acid bacteria (LAB)-Lactococcus (L.) lactis, Lactobacillus (Lb.) plantarum, Lb. casei, Lb. brevis, Leuconostoc (Leu.) mesenteroides, Lb. fermentum, Lb. buchneri, and Lb. curvatus-to assess their glutamic acid production pathways. Glutamic acid is important for umami taste in foods. The only genes for glutamic acid production identified in the eight LAB were for conversion from glutamine in L. lactis and Leu. mesenteroides, and from glucose via citrate in L. lactis. Thus, L. lactis was considered to be potentially the best of the species for glutamic acid production. By biochemical analyses, L. lactis HY7803 was selected for glutamic acid production from among 17 L. lactis strains. Strain HY7803 produced 83.16 pmol/μl glutamic acid from glucose, and exogenous supplementation of citrate increased this to 108.42 pmol/μl. Including glutamic acid, strain HY7803 produced more of 10 free amino acids than L. lactis reference strains IL1403 and ATCC 7962 in the presence of exogenous citrate. The differences in the amino acid profiles of the strains were illuminated by principal component analysis. Our results indicate that L. lactis HY7803 may be a good starter strain for glutamic acid production.

• Journal of Microbiology and Biotechnology
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• 제9권2호
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• pp.201-205
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• 1999

The effects of growth temperature and a carbon source on the expression of $\beta$-galactosidase gene of Lactococcus lactis ssp. lactis ATCC 7962 (L. lactis 7962) were investigated. At $25^{\circ}C$, L. lactis 7962 had a higher $\beta$-galactosidase activity than cells grown at $30^{\circ}C$ or $37^{\circ}C$, although cells grew most quickly at $37^{\circ}C$ The highest $\beta$-galactosidase activity was observed in cells grown in M17 with lactose (l %) followed by cells grown in a galactose (1 %) medium. L. lactis 7962 exhibited the minimum $\beta$-galactosidase activity in glucose media, indicating catabolite repression. When the cellular levels of $\beta$-galactosidase mRNA were examined using slot blot hybridization, no significant differences were observed between cells grown at $25^{\circ}C$ and cells at $30^{\circ}C$ or $37^{\circ}C$ in the same media. This suggests that the quantity of $\beta$-galactosidase mRNA may not be the reason for the higher $\beta$-galactosidase activities of L. lactis 7962 at $25^{\circ}C$ The level of ccpA (Catabolite Control Protein) transcript remained almost constant during the exponential growth phase irrespective of a carbon sourse.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.157-161
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• 2002

A lactic acid bacteria with ${\beta}$-gal activity was isolated from Kimchi, a traditional fermented vegetable food in Korea. The isolate was identified as a Lactococcus lactis strain and named L. lactis A2. The gene encoding ${\beta}$-gal of L. lactis A2 was cloned as a 5.8 kb PstI fragment. DNA sequencing identified the complete lacA (galactoside acetyltransferase)-lacZ (${\beta}$-galactosidase) genes together with the 3' part of upstream galT (galactose-1-phosphate uridyltransferase), and the 5'region of downstream galE (UDP-galactose-4-epimerase) genes. L. lactis A2 had the same gal/lac operon structure as in L. lactis subsp. lactis 7962. Other genes of the Leloir pathway are most likely to be located in the 5'upstream of the 5.8 kb fragment on the A2 chromosome. Sequences downstream of galE were different from those of L. lactis subsp. lactis 7962.

• Preventive Nutrition and Food Science
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• 제2권2호
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• pp.101-108
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• 1997

A lactic acid bacterium LAB3113, isolated from traditionally fermented Kimchi was found to produce bacteriocin whose activity was very specific toward lactobacilli and not effective against any other bacteria. Lactobacilli affected by the inhibitory substance included Lactobacillus delbrueckii-lactis, L. johnsonii, L. gsseri, and L. curvatus. Based upon biochemical and physiological characteristics, LAB3113 was classified as Lactococcus lactis, and its bacteriocin was named as lactococcin K3113. Lactococcus lactis. LAB3113 produced bacteriocin at th early stage of growth and the concentration of the bacteriocin did not decrease even after alt stationalry phase. Optimal temperature of bacteriocin production was $25^{\circ}C$ at the initial pH 7.0. Partially purified lactococcin K3113 was completely inactivated by protease, but not affected by lipase, lysozyme and RNase. The bacteriocin was very heat-stable even after autoclaving for 20 min. It was also stable in pH changes, an was not affected by th presence of solvents. lacotococcin K3113 appeared to act in bactericidal mode against L. delbrueckii-lactis ATCC4797. Molecular weight of lactococcin K3113 was calibrated as 10,500 dal by SDS-PAGE an activity staining. Lactococcus lactis LAB3113 had four residential plasmids of 3.7kb, 11.2kb, 15.5kb, and 48kh in molecular sizes. Plasmid profile analysis of mutant strain revealed that 15.5 kb plasmid was re-sponsible for the production of lactococcin K3113 and its immunity to the bacteriocin.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1697-1701
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• 2015

The anticancer and anti-inflammatory activities of probiotic Lactococcus lactis NK34 were demonstrated. Treatment of cancer cells such as SK-MES-1, DLD-1, HT-29, LoVo, AGS, and MCF-7 cells with 10⁶ CFU/well of L. lactis NK34 resulted in strong inhibition of proliferation (>77% cytotoxicity, p < 0.05). The anti-inflammatory activity of L. lactis NK34 was also demonstrated in lipopolysaccharide-induced RAW 264.7 cells, where the production of nitric oxide and proinflammatory cytokines (tumor necrosis factor-α, interleukin-18, and cyclooxygenase-2) was reduced. These results suggest that L. lactis NK34 could be used as a probiotic microorganism to inhibit the proliferation of cancer cells and production of proinflammatory cytokines.