• Journal of Microbiology
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• v.39 no.1
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• pp.11-16
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• 2001

Tentative identification of Leuconostoc lactis IH23 isolated from kimchi (a fermented vegetable product) has been described previously with 16S rDNA sequencing (Choi, 1., M. Sc. Thesis Inha Univ.1999). This strain produced the slime identified as dextran based on IR, $\^$13/C- and $^1$H-NMR spectroscopic results. Further study proved that the isolate IH23 belongs to a homogeneous genetic group with L. lactis DSM 20202$\^$T/ and L. argentinum DSM 8581$\^$T/. The results showed DNA-DNA homology of 99-100%, 16S rDNA gene sequence similarity (97.7% ), and a phylogenetic relationship although L. argentinum DSM 8581$\^$T/ had lower homology (80-91%). These data indicate that L. argentinum DSM 8581$\^$T/ and the isolate IH23 belong to an identical species with L. lactis DSM 20202$\^$T/at the genetic level, although in carbohydrate fermentation, the isolate IH23 was mast closely related to L. argentinum DSM 8581$\^$T/ and quite different from L. lactis DSM 20202$\^$T/. Here we first report the isolation of consistent phenotypic variation in Leuconostoc lactis. We also emphasize that the nomenclature of subspecies needs to be differentiated into the three strains mentioned above in Leuconostoc lactis.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.134-138
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• 2003

The secondary and tertiary structures of ${\beta}$-galactosidase from L. lactis ssp. lactis 7962 were designed using Nnpredict and Sybyl version 6.3. By using site-directed mutagenesis, the mutated enzymes, Tyr-475-phe and Glu-506-Asp, were generated based on the structural modeling of L. lactis ssp. lactis 7962. The enzymes Tyr.-475-Phe and Glu-506-Asp had <$1\%$ of the activity of the native enzyme with ONPG as substrate. The $V_{max}$ values of the mutated enzymes were greatly reduced (1,800~40,000-1314) compared with the value for the native ${\beta}$-galactosidase. However, the $K_m$ values of Tyr-475-Phe and Glu-506-Asp with ONPG, PNPG, PNPF, and PNPA were not significantly different from those of the native enzyme. The results obtained support the suggestion that Tyr-475 and Glu-506 constitute very important parts of the catalytic machinery of the ${\beta}$-galactosidase.

• Journal of Microbiology
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• v.41 no.2
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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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• v.6 no.1
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• pp.50-53
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• 1996

A cultured milk product was made by fennenting 10$\%$ reconstituted skim milk with Lactococcus lactis subsp. lactis TA29 and Saccharomyces exiguus SK2. L. lactis TA29 and S. exiguus SK2 grew up to 1.0 $\times 10^9\;and\;2.0 \times 10^6$ cfu/ml, respectively. After the fermentation 21$\%$ of lactose was hydrolyzed, pH was lowered to 4.2, and titratable acidity and alcohol concentration were increased to 0.96 and 0.023$\%$, respectively. When the fermented milk was stored at $4{\circ}C$ for 9 days, the viable cell counts for L. lactis TA29 and S. exiguus SK2 were $6.5 \times 10^5\;and\;1.6 \times 10^6$ cfu/rnl, respectively. The alcoholic fermented milk prepared in this experiment was more inhibitory against some pathogenic bacteria including C. perfringens than commercial yoghurt products tested.

• Microbiology and Biotechnology Letters
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• v.14 no.6
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• pp.487-493
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• 1986

Lactobacillus helveticus YM-1and Streptococcus lactis Ml$_3$ were inoculated together in reconstituted non-fat skim milk medium, and then their proteolytic activity and stimulatory compound for acid production were investigated. Significant difference between Lactobacillus helveticus YM-1 and Streptococcus lactis Ml$_3$was observed in the proteolytic activities. The proteolytic activity of Lactobacillus helveticus YM-1 and Streptococcus lactis Ml$_3$ was 105 $\mu\textrm{g}$/$m{\ell}$ and 30 $\mu\textrm{g}$/$m{\ell}$ when converted the amounts of hydrolysates of milk protein determined by Folin Ciocaleau phenol method into their tyrosine equivalent Stimulatory compounds in cell-free filtrate of Lactobacillus helveticus YM-1were identified as peptide with a molecular weight of approximately 4, 300 for the acid production by Streptococcus lactis Ml$_3$. Some kinds of amino acids, such as histidine, lysine, arginine and glutamic acid, were rich in acid hydrolysates of peptide. Among amino acids, histidine, glutamic acid and phenylalanine stimulated acid production, on the contrary isoleucine inhibited.

• Microbiology and Biotechnology Letters
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• v.51 no.1
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• pp.53-58
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• 2023

The glutamic acid producing strain for development savory taste enhancing foods was identified the possibility through application into soybean fermentation. To check the effects on glutamic acid production during soybean fermentation, Lactococcus lactis HY7803 was introduced as a starter. The soybean samples were analyzed on days 0, 7, 14 and 21. The numbers of bacteria decreased gradually, while the content of amino-type nitrogen increased during fermentation in the soybean with L. lactis HY7803. Glutamic acid content in soybeans with L. lactis HY7803 increased from 114.99 ± 9.37 pmol/ul on day 0 to 138.14 ± 1.76 pmol/ul on day 21, showing an overall higher amino acid content than soybeans without L. lactis HY7803 and similar content to soybeans with Aspergillus oryzae SNU-G. It was clearly distinguished through principal component analysis. Consequently, our results indicate that L. lactis HY7803 is available as a fungus replacement and may be a good starter strain for enhancing savory taste in vitro as well as soybean fermentation.

• Journal of Microbiology and Biotechnology
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• v.21 no.2
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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.

• Food Science and Biotechnology
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• v.16 no.5
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• pp.843-847
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• 2007

Strain NK34 was characterized for probiotic use. Strain NK34 was named Lactococcus lactis NK34 based on API 50 CHL kit results and 16S rDNA sequencing. L. lactis NK34 was highly resistant to artificial gastric juice (pH 2.5) and artificial bile acid. Based on results from the API ZYM kit, 4 enzymes were produced. L. lactis NK34 was resistant to all antibiotics tested except for $10\;{\mu}g/mL$ roxithromycin and $10\;{\mu}g/mL$ erythromycin. The cholesterol-lowering effect of L. lactis NK34 was about 46.9%. Concentrations of interleukin $(IL)-1{\alpha}$ in the $20{\times}$ concentrated supernatant of L. lactis NK34 was about 361 pg/mL. L. lactis NK34 was also found to inhibit the growth of colon cancer cells due to MNNG-induced DNA damage. These results demonstrate the potential of L. lactis NK34 as a health-promoting probiotic.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.924-927
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• 2003

This study was conducted to investigate the application of bifidobacteria on kimchi. Among several Bifidobacterium species, we selected Bifidobacterium lactis (DSM 10140), which is resistant to oxygen, acid and salt. Bifidobacterium lactis was cultured in a supplemented deMan, Rogosa and Sharpe (SMRS) medium under aerobic conditions. Its acid-tolerance and salt-tolerance were pH 3.0 and 3.5% (NaCl), respectively. The viability of Bifidobacterium lactis added to kimchi was confirmed by PCR, using specific primers on Bifidobacterium lactis. In sensory evaluation, kimchi containing Bifidobacterium lactis showed similar scores in overall acceptability with the control kimchi. Consequently, these results showed that it would be possible to prepare functional kimchi using Bifidobacterium.

• Food Science of Animal Resources
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• v.42 no.1
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• pp.46-60
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• 2022

In this study, angiotensin-I-converting enzyme inhibitory (ACEI) activity was evaluated in fermented goat milk fermented by lactic acid bacteria (LAB) from fermented foods and breast milk. Furthermore, the potential for ACEI peptides was identified in fermented goat milk with the highest ACEI activity. The proteolytic specificity of LAB was also evaluated. The 2% isolate was inoculated into reconstituted goat milk (11%, w/v), then incubated at 37℃ until pH 4.6 was reached. The supernatant produced by centrifugation was analyzed for ACEI activity and total peptide. Viable cell counts of LAB and titratable acidity were also evaluated after fermentation. Peptide identification was carried out using nano liquid chromatography mass spectrometry (LC-MS/MS), and potential as an ACEI peptide was carried out based on a literature review. The result revealed that ACEI activity was produced in all samples (20.44%-60.33%). Fermented goat milk of Lc. lactis ssp. lactis BD17 produced the highest ACEI activity (60.33%; IC₅₀ 0.297±0.10 mg/mL) after 48 h incubation, viable cell counts >8 Log CFU/mL, and peptide content of 4.037±0.27/mL. A total of 261 peptides were released, predominantly derived from casein (93%). The proteolytic specificity of Lc. lactis ssp. lactis BD17 through cleavage on the amino acid tyrosine, leucine, glutamic acid, and proline. A total of 21 peptides were identified as ACEI peptides. This study showed that one of the isolates from fermented food, namely Lc. lactis ssp. lactis BD17, has the potential as a starter culture for the production of fermented goat milk which has functional properties as a source of antihypertensive peptides.