• Journal of Microbiology and Biotechnology
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• 제13권2호
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• pp.202-206
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• 2003

To determine the effect of immunopotentiating activity of cellular components of Lactococcus lactis ssp. lactis, the immune function was analyzed in vitro using mice cells. When stimulated with mitogens, productions of $IFN-{\gamma}$, IL-12, $TNF-{\alpha}$, and IL-6 were enhanced in spleen cells treated with cellular components, with IL-4 production being the highest in spleen cells treated with cytoplasm fraction. Without mitogen stimulation, the productions of $IFN-{\gamma}$ and IL-12 were the highest in spleen cells treated with heat-killed whole cell. $TNF-{\alpha}$ and IL-6 productions were also high in spleen cells treated with all cellular components. Only heat-killed whole cell showed significant enhancement in natural killer cell activity. In peritoneal exudates cells, $TNF-{\alpha}$ production was enhanced significantly by all cellular components of Lactococcus lactis ssp. lactis These results indicate that the cellular components of Lactococcus lactis ssp. lactis are capable of stimulating immune cells to produce cytokines, and that both their cell walls and cytoplasm fraction contribute to these capacities.

• 한국미생물·생명공학회지
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• 제19권6호
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• pp.619-623
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• 1991

Lactococcus lactis ssp. lactis ML8(L.lactis ML8)의 nisin 생산과 저항 특성을 구명하기 위하여 배지의 종류 및 pH가 nisin의 역가에 미치는 영향, 균체의 생육에 따른 nisin의 생산특성, nisin이 균체생육에 미치는 영향 및 $Ca^[2+}$ 이온의 존재가 균주의 nisin 저항성에 미치는 영향을 조사하였다. Nisin의 역가를 Micrococcus flacus에 대하여 항생효과를 나타내는 성질을 이용하여 agar diffusion법으로 측정하였을 때, M.flavus 생육에 대한 저해직경은 nisin 농도 (0.5`20 unit/ml)의 log치에 비례하였다.

• Preventive Nutrition and Food Science
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• 제5권3호
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• pp.153-159
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• 2000

A 4.4 kb DNA fragment encompassing lacA (galactoside acetyltransferase) and lacZ($\beta$-galactosidase) genes from Lactococus lactis ssp. lactis ATCC 7962 (L. lactis 7962) was introduced ito a Lac strain, Lactococcus lactis ssp. lactis MG1363 (L. lactis MG1363) by using a lactococcal expression vector, pMG36e and expression level of lacZ was examined. Growth rates and $\beta$-galactosidase ($\beta$-gal) activities of MG1363 cells carrying recombinant plasmid, pMLZ3, on M17 broth containing different carbon sources (1%, w/v) were examined. Contrary to the expectations, MG1363 [pMLZ3] grown on lactose showed the lowest enzyme activity (17 units) and cells grown on galactose had the highest $\beta$-gal activity (41 units). Cells grown on glucose had intermediate activity (33 units). These activities are about one tenth of the values observed in L. lactis 7962 where lacZ is present as a single-copy gene in the chromosome. When the cellular concentrations of lacZ transcript were examined using slot blot hybridization, it was found that MG1363[pMLZ3] produced sufficient amounts of transcript. These results indicate that either proteolytic degradation of $\beta$-gal or other regulatory mechanism prevent the translation or accumulation of $\beta$-gal in L. lactis MG1363 cells. In regard to regulation, the presence of the ccpA gene in L. lactis MG1363 was confirmed by Southern blot.

• Journal of Microbiology and Biotechnology
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• 제16권5호
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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.

• Journal of Microbiology and Biotechnology
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• 제9권4호
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• pp.393-397
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• 1999

The gene (galE) encoding UDP-galactose-4-epimerase, operative in the galactose metabolic pathway, was cloned together with the $\beta$-galactosidase gene (lacZ) from Lactococcus lactis ssp. lactis ATCC7962 (L. lactis 7962). galE was found to have a length of 981 bps and encoded a protein with a molecular mass of 36,209 Da. The deduced amino acid sequence showed a homology with GalE proteins from several other microorganisms. A Northern analysis demonstrated that galE was constitutively expressed by its own promoter. When galactose or lactose was added into medium, the galE transcription was induced by several upstream promoters. The structure of the gal/lac operon of L. lactis 7962 was partially characterized and the gene order around galE was galT-lacA-lacZ-galE-orfX.

• Journal of Microbiology and Biotechnology
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• 제4권3호
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• pp.191-194
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• 1994

Acetoin and ammonia, the precursors of tetramethylpyrazine (TMP) having "nutty " or "roasted" flavors, were produced by cultivating Lactococcus lactis ssp. lactis biovar. diacetilactis FC1. The effects of the volume concentration ratio (VCR) of cell-free medium on the formation of TMP were investigated using a rotary evaporator at $70^{\circ}C than at 80^{\circ}C$. As the VCR increased, the formation of TMP and the conversion ratio of acetoin to TMP increased. More TMP were formed at $70^{\circ}C than at 80^{\circ}C$. As the VCR increased, the concentration of acetoin decreased implying the formation of TMP from acetoin and ammonia.

• Journal of Microbiology and Biotechnology
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• 제1권4호
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• pp.281-284
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• 1991

To investigate the optimum conditions for the production of ammonia as a precursor of tetramethylpyrazine flavor compound from arginine by Lactococcus lactis ssp. lactis biovar. diacetilactis FC1, fermentation factors such as initial pH of culture media, fermentation temperature, concentration of arginine-HC1, and sugars were examined. The optimum conditions were initial pH 5.5 of the culture media, fermentation temperature of $34^{\circ}C$, 6% (w/v) of arginine-HC1, and 1% (w/v) of galactose as a carbon source. Under the optimum fermentation conditions, 40 mmole/l of ammonia was produced after 40 h.

• Journal of Microbiology and Biotechnology
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• 제10권6호
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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.

• Food Science and Biotechnology
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• 제14권3호
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• pp.405-409
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• 2005

Cellular components of Lactococcus lactis ssp. lactis (heat-killed whole cells, cytoplasm, and cell walls) were tested for their in vivo immunopotentiating activities. Peritoneal macrophages from mice injected intraperitoneally with cell-wall fractions exhibited significantly greater phagocytic activity than groups injected with whole cells or cytoplasm fraction. Cytotoxicity of natural-killer cells was highest in cytoplasm fractions. Production of cytokines (IFN-${\gamma}$, IL-2, IL-6, and IL-12) in spleen cells was significantly higher when cellular components were injected intraperitoneally, and tended to be higher in whole-cell and cytoplasm groups than in cell-wall group. These results demonstrate lactic acid bacteria whole cells and their cytoplasm and cell-wall tractions have immunopotentiating activities.

• 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.