• 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.

• Journal of Microbiology and Biotechnology
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• v.7 no.5
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• pp.293-298
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• 1997

A 4.6-kb HindIII fragment encompassing the complete 140-kDa ${\alpha}$-amylase gene of Lactobacillus amylovorus B 4540 was cloned into pBR322 by the shot gun method. Southern blotting and restriction mapping for the insert were performed. The recombinant 9.0-kb plasmid, pFML1, conferred ${\alpha}$-amylase activity to E. coli and Lactococcus lactis hosts when introduced by electroporation. SDS-PAGE and zymography confirmed the production of 140-kDa ${\alpha}$-amylase and its proteolytic degradation products with enzyme activity in transformants. Total ${\alpha}$-amylase activity of E. coli $DH5{\alpha}$ cells harboring pFML1 was 1.8 units and most activity was detected from cell pellets. Total enzyme activity of L. lactis subsp. lactis MG1363 transformant was five to ten-fold lower than that of E. coli cell but more than half of the activity was detected in the culture supernatant.

• Journal of Life Science
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• v.25 no.2
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• pp.180-188
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• 2015

The bacterial strain isolated from Kimchi showed antibacterial activity against Micrococcus luteus IAM 1056. The selected strain was identified as Lactococcus lactis by 16S rRNA nucleotide sequence analysis and named as Lactococcus sp. KD 28. The treatment of culture supernatant with proteinase K removed antibacterial activity, indicating its proteinaceous nature, a bacteriocin. This bacteriocin was sensitive to hydrolytic enzymes such as ${\alpha}$-chymotrypsion, trypsin, proteinase K, lipase, ${\alpha}$-amylase and subtilisin A. The bacteriocin was highly thermostable and resistant to heating at $80^{\circ}C$ for up to an hour but 50 % of the total activity was remained at $100^{\circ}C$ for 30 min. The pH range from 2.0 to 8.0 had no effect on bacteriocin activity and it was not affected by solvents such as acetonitrile, isopropanol, methanol, chloroform and acetone up to 50% concentration. The bacteriocin showed antibacterial activity against M. luteus IAM 1056, Lactobacillus delbrueckii subsp. lactis KCTC 1058, Enterococcus faecium KCTC 3095, Bacillus cereus KCTC 1013, B. subtilis KCTC 1023, Listeria ivanovii subsp. ivanovii KCTC 3444, Staphylococcus aureus subsp. aureus KCTC 1916, B. megaterium KCTC 1098 and B. sphaericus KCTC 1184. The bacteriocin was purified through ammonium sulfate concentration, SP-Sepharose chromatography and RP-HPLC. The molecular weight was estimated to be about 3.4 kDa by tricine-SDS-PAGE analysis.

• Journal of Korean Medicine for Obesity Research
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• v.16 no.1
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• pp.11-18
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• 2016

Objectives: To confirm microbiological change and cytoprotective effect of Samjung-hwan (SJH) which fermented by Lactic acid bacteria from natural fermented SJH. Methods: SJH was fermented by Lactobacillus brevis and Lactococcus lactis subsp. lactis from natural fermented SJH. After 1 week of fermentation, we analysed pH and microbial profiling. We also performed measuring total polyphenol total flavonoid contents and 1,1-Diphenyl-2-picryhydrazyl (DPPH) free radical scavenging activity to investigate antioxidant ability. Cell viability was performed by using HepG2 cell. Results: pH of lactic acid bacteria inoculated group and non-inoculated group was decreased and total counts of lactic acid bateria for both group was increased after fermentation of SJH. Total polyphenol and flavonoid contents and DPPH free radical scavenging activity was increased in both group. Total polyphenol contents of lactic acid bacteria Inoculated group is more increased than non-inoculated group. HepG2 cell viability was increased in both group. Conclusions: SJH fermentd by Lactobacillus brevis and Lactococcus lactis subsp. lactis shows change in microbiological character and has cytoprotective effect. Further studies are required for investigating function of lactic acid bacteria during fermentation of SJH.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1433-1442
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• 2018

To identify and quantify the effects of a combination of dietary $1{\times}10^8CFU/g$ Lactococcus lactis subsp. lactis I2 ($LI_2$) and 0.1% ${\beta}$-glucooligosaccharides (BGO) on the growth and immunity of olive flounder (Paralichthys olivaceus), a feeding experiment was conducted. Flounder ($14{\pm}0.5g$) were divided into two groups and fed control and synbiotic feeds for 8 weeks. Investigations were carried out on growth and feed utilization, innate immunity, serum biochemical parameters, intestinal lactic acid bacterial (LAB) viability, microvillus length, and changes in the expression levels of genes encoding pro-inflammatory cytokines (tumor necrosis factor $[TNF]-{\alpha}$, interleukin $[IL]-1{\beta}$, and IL-6). Results demonstrated the synbiotic diet had significantly better (p < 0.05) responses in terms of weight gain and specific growth rate, three innate immune parameters (respiratory burst, serum lysozyme, and superoxide dismutase), intestinal LAB viability, and the relative $TNF-{\alpha}$ expression level (p < 0.05). Moreover, after challenge with Streptococcus iniae ($1{\times}10^8CFU/ml$), the synbiotically fed group exhibited significantly higher (p < 0.05) protection against streptococcosis, validating the observed changes in immune parameters and induction of the cytokine-encoding gene. Therefore, according to the results of the present study, synbiotic feed ($LI_2+BGO$) increased growth, modulated innate immune parameters and protected olive flounder against streptococcosis.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.171-178
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• 2021

In this study, exosomal-like nano-vesicles derived from probiotics were isolated and various physiological activities were evaluated on the skin. This study show that Lactococcus lactis subsp. lactis (LL) are incubated, and then isolated LL derived exosomal nanovesicles (LVs) at the range of 70 ~ 200 nm by high-pressure homogenizer and ultrafiltration. The vesicle numbers were an average of 1.81 × 10¹¹ particles/mL. This study finds out the bacterial nanovesicles' beneficial effect on the skin. Fibrillin (FBN1) gene expression increased by 23% in fibroblast cells. Fibronectin (FN1) and filaggrin (FLG) gene expression increased by 65% and 400% in keratinocytes. We could see that cornified envelope (CE) formation ability was increased by 30% compared to the control group. Furthermore, collagen type I alpha 1 (COL1A1) protein expression increased by 83% compared to the UV-irradiated control group. These results suggest that LVs could help skin barrier improvement and used as an ingredient for cosmetics or pharmaceuticals.

• Food Science of Animal Resources
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• v.28 no.1
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• pp.82-90
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• 2008

Two strains of pure lactic acid bacteria capable of forming both acid and slime were isolated from the kefir made of goat milk. The isolated strains observed by morphological and physiological properties, and their 16S rDNA partial sequence were identified as Streptococcus salivarius subsp. thermophilus(LFG-1) and Lactococcus lactis subsp. lacits(LFG-2) with over 99% homology. The optimum temperature of Str. salivarius subs. thermophilus LFG-1 for growth was $40-45^{\circ}C$, and its generation time was 40.6 minutes. The final pH of cultured broth by Str. salivarius subsp. thermophilus LFG-1 and the commercial strain Str. thermophilus Body-1 for 24hr at $37^{\circ}C$ were 4.30 and 4.55, respectively. The coagulative activity of Str. salivarius subsp. thermophilus LFG-1 was almost as strong as that of commercial strain Str. thermophilus Body-1. However, the LFG-2 strain showed lower coagulative activity than Str. thermophilus Body-1. The survival rate of lactic acid bacteria were between 22-29% in 0.3% bile extract. At pH 1.0 all of the bacteria were killed, and most of lactic acid bacteria died against pH 3.0. However, all lactic acid bacteria survived well at pH 4.5.

• Journal of Microbiology and Biotechnology
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• v.28 no.8
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• pp.1293-1298
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• 2018

Phosphomannomutase (ManB) converts mannose-6-phosphate (M-6-P) to mannose-1-phosphate (M-1-P), which is a key metabolic precursor for the production of GDP-D-mannose used for production of glycoconjugates and post-translational modification of proteins. The aim of this study was to express the manB gene from Escherichia coli in Lactococcus lactis subsp. cremoris NZ9000 and to characterize the encoded enzyme. The manB gene from E. coli K12, of 1,371 bp and encoding 457 amino acids (52 kDa), was cloned and overexpressed in L. lactis NZ9000 using the nisin-controlled expression system. The enzyme was purified by Ni-NTA column chromatography and exhibited a specific activity of 5.34 units/mg, significantly higher than that of other previously reported ManB enzymes. The pH and temperature optima were 8.0 and $50^{\circ}C$, respectively. Interestingly, the ManB used in this study had two substrate specificity for both mannose-1-phosphate and glucose-1-phosphate, and the specific activity for glucose-1-phosphate was 3.76 units/mg showing 70% relative activity to that of mannose-1-phosphate. This is the first study on heterologous expression and characterization of ManB in lactic acid bacteria. The ManB expression system constructed in this study canbe used to synthesize rare sugars or glycoconjugates.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.829-835
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• 2000

The ptsH and ptsI genes of Lactococus lactis subsp. lactis ATCC 7962 (L. lactis 7962), encoding the general proteins of phosphotransferase system (PTS) components, HPr and enzyme I, respectively, were cloned and characterized. A 1.3 kb PCR product was obtained using a primer set that was hybridized to the internal region of the L. lactis 7962 pts HI genes and then subcloned into a low-copy number vector, pACYC184. The 5' upstream and 3' downstream region from the 1.3 kb fragment were subsequently clone using the chromosome walking method. The complete ptsHI operon was constructed and the nucleotide sequences determined. Two ORFs corresponding to HPr (88 amino acids) and enzyme I (575 amino acids) were located. The ptsHI genes of L. lactis 7962 showed a very high homology (84-90%) with those genes from other Gram-positive bacteria. A primer extension analysis showed that the transcription started at either one of two adjacent bases upstream of the start codon. Using a Northern analysis, two transcripts were detected; the first, a 0.3 kb transcript corresponding to ptsH and the second, a 2 kb transcript corresponding to ptsH and ptsI. The transcription level of ptsH was higher than that of ptsI. The concentration of the ptsH transcript in cells grown on glucose was similar to that in cells grown on lactose, yet higher than that in cells grown on galactose. The ptsI transcript was scarcely detected in cell grown on lactose or galactose. The ptsI transcript was scarcely detected in cells grown on lactose or galactose. The results of a sequence analysis and Northern blot confirmed that the ptsH and ptsI genes of L. lactis 7962 were arranged in an operon like other known ptsHI genes and the expression of the ptsHI genes was regulated at the transcriptional level in response to the carbon source.

• Microbiology and Biotechnology Letters
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• v.30 no.2
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• pp.116-122
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• 2002

The partial 165 rDNA sequences of 6 lactic acid bacterial strains isolated from Kimchi were determined. Two strains were Leuconostoc mesenteroides and the rest were incorrectly classified and turned out to be Lactobacillus. As the case of dairy lactic acid bacteria, the strains isolated from Kimchi also had cell-envelope proteinase (CEP) activity. As the result of partial CEP gene amplification with CEP-specific primers, the expected 1.2-kb amplificate was obtained not from Leu. mesenteroides but from Lactobacillus strains. The deduced amino acid sequence of PCR product amplified from the genomic DNA of Lactobacillus pentosus KFR1821 showed 95％ and 92％ homology with those of PrtPs from Lactococcus lactis subsp. cremoris and Lactobacillus paracasei subsp. paracasei, respectively. The PCR amplificate was used as a probe and the result of Southern hybridization illuminated the location of CEP gene in chromosomal DNA of Lb. pentosus KFR1821.