• Journal of Microbiology and Biotechnology
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• v.1 no.4
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• pp.285-287
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• 1991

To produce the tetramethylpyrazine (TMP) flavor compound, Lactococcuss lactis subsp. lactis biovar. diacetilactis (L. diacetilactis) FC1 was cultivated in the TMP medium containing 3% (w/v) of Na-citrate and 6% (w/v) arginine-HC1 as substrates of acetoin and $NH_3$, respectively, which are the two precursors of the TMP. After 19-day fermentation at $34^{\circ}C$, 0.57 g/l or 4.19 mmole/l of the TMP was produced. This was the first result showing that the TMP could be produced by L. diacetilactis.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.11
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• pp.1680-1685
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• 2003

Antimutagenicity of milk cultured with lactic acid bacteria isolated from dadih on the mutagenicity of heated salty and sweet tauco was examined using streptomycin dependent (SD) 510 strain of Salmonella typhimurium TA 98 as a tester culture. Cultured milk samples exhibited widely antimutagenic activity against mutagenic heated salty and sweet tauco. Lc. lactis subsp. lactis R-22, Lc. lactis subsp. casei R-35, Lc. lactis subsp. casei R-52 and E. faecalis subsp. liquefaciens R-55 exhibited no inhibitory effect on the mutagenic heated salty tauco. Mutagenicity of heated sweet tauco was inhibited by cultured milks stronger than that of heated salty tauco. Milk cultured with Lc. lactis subsp. cremoris R-48, Leuc. mesentroides R-51 and Lc. lactis subsp. casei R-68 showed high inhibition against the mutagenicity of both heated salty and sweet taucos. Antimutagenic activity of the cultured milks against mutagenic heated tauco was attributed to the bacterial cells. Among the three strains which showed high antimutagenicity, only Leuc. mesentroides R-51 was tolerant to both acid and bile; so this strain can be used as probiotic in preventing the occurrence of mutagenesis caused by mutagenic heated food like tauco.

• 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 environmental and Sanitary engineering
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• v.12 no.1
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• pp.85-95
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• 1997

Behavior of Listeria monocytogenes in Skim milk during fermentation by Lactobacillus bulgaricus YI-2 and Streptococcus lactis FYI-1 were determined. Autoclaved skim milk was inoculated with ca. 10$^{3}$ L. monocytogenes (Strain LM91-1 or LM 96-2) cells/ml, and with 5.0, 1.0, 0.5 or 0.1% of a milk culture of either L. bulgaricus TI-2 or S. lactis FYI-1. Skim milk containing ca. 10$^{3}$ L. monocytogenes was incubated at 37 or 42$\circ $C for 15 h with L. bulgaricus YI-2, and at 21 or 30$\circ $C for 15 h with S. lactis FYI-1. Cultured skim milks were stored at 4$\circ $C in the refrigerater. Samples were plated on Oxford Agar with oxford antimicrobic supplement to enumerate L. monocytogenes and on either modified MRS agar to enumerate lactic acid bacteria. L. monocytogenes survived the 15-h fermentation with S. lactis FYI-1 in all combinations of level of inoculum and temperature of incubation, but inhibition of growth ranged from 94 to 100%. When incubated with over the 1.0% of L. bulgaricus, L. monocytogenes inhibited or disappeared in fermented skim milk from 9 h after incubation. Especially, incubation at 42$\circ $C with 5.0% L. bulgaricus YI-2 as inoculum appeared to be the most effective inhibitory combination for strain LM 91-1, causing 100% inhibition in growth based on maximum papulation attained. In most instances of incubated with L. bulgaricus YI-2, growth of the pathogene appeared to be completely inhibited when the pH dropped below 4.38.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.327-332
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• 1994

Optimum conditions for the production of acetoin and ammonia as the precursors of tetramethylpyrazine(TMP) were determined using Lactococcus lactis subsp. lactis biovar. diacetylactis FC1 in a modified Lactose-citrate broth containing galactose, citrate, and arginine. The cell growth and the productivity of acetoin and ammonia were remarkably increased in an aerobic culture with 10 $\mu M$ of hematin. For the optimum conditions of acetoin and ammonia production, the concentration of citrate and arginine were adjusted to 156 mM and 50 mM after 18 hr cultivation, and citrate and galactose to 156 mM and 50 mM after 36 hr cultivation, respectively. In these conditions, acetoin and ammonia were produced to the final concentration of 127 mM and 195 mM, which were the highest concentations, respectively. The optimum conditions of the TMP production were also determined as follows; 4 hours at 121, pH 8.3, and the maximal yield of TMP under these conditions was 0.81 g/l.

• Food Science and Biotechnology
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• v.14 no.3
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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.

• Preventive Nutrition and Food Science
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• v.2 no.2
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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 the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.583-592
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• 2001

This study was undertaken to evaluate the clinical effect of inhibiting plaque formation of Lactococcus lactis 1370, a acid producing bacterium residing in the mouth. 30 children were asked to use 10ml of control mouth-wash and mouthwash containing Lactococcus lactis 1370. The plaque index and plaque area rate at 24h and 48h after the use of the mouthwashes were measured. And the number of Lactococcus lactis 1370 was counted at 1h, 3h, and 6h in the mouth. The results are as follow. 1. The mean plaque index at 24h after the use of the control mouthwash and the mouthwash containing Lactococcus lactis 1370 were 2.43 and 2.06, respectively. The inhibiting rate of plaque formation was 15% (P<0.05). 2. The mean plaque index at 48h after the use of the control mouthwash and the mouthwash containing Lactococcus lactis 1370 were 2.95 and 2.17, respectively. The inhibiting rate of plaque formation was 26%, showing more decrease than at 24h(P<0.05). 3. The mean plaque area rate at 24h after the use of the control mouthwash and the mouthwash containing Lactococcus lactis 1370 were 21.2% and 15.6%, respectively. The inhibiting rate of plaque formation was 26% (P<0.05). 4. The mean plaque area rate at 48h after the use of the control mouthwash and the mouthwash containing Lactococcus lactis 1370 were 33.0% and 17.8%, respectively. The inhibiting rate of plaque formation was 46% (P<0.05). 5. The number of Lactococcus lactis 1370 in the mouth decreased significantly from mouthwashing to 3h, but increased slightly between 3h and 6h. As seen with the above results, we think that using the mouth wash with Lactococcus lactis 1370 would prevent the formation of plaque in the mouth and can be an effective method to prevent dental caries and periodontal disease.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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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.

• Microbiology and Biotechnology Letters
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• v.41 no.4
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• pp.391-397
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• 2013

A putative cyclomaltodextrinase (LLCD) gene was cloned from the genome of Lactococcus lactis subsp. lactis KCTC 3769 (ATCC 19435), which encodes 584 amino acids with the predicted molecular mass of 68.7 kDa. KCTC 3769 shares approximately 40% of amino acid sequence identity with the CDase-family of enzymes. The dimeric enzyme with C-terminal six-histidines was heterologously expressed and purified from recombinant E. coli. LLCD showed the highest activity against ${\beta}$-cyclodextrin (CD) at pH 7.0 and $37^{\circ}C$. In particular, LLCD exhibited extremely low activity against starch and pullulan, while its CD-hydrolyzing activity was about 80 times higher than starch. Due to its much higher activity on CD over starch, LLCD has been identified as a member of CDases. However, LLCD can be distinguished from the other common CDases on the basis of its extremely low hydrolyzing activity against starch, pullulan, and acarbose.