• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2001.06a
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• pp.154-154
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• 2001

• Microbiology and Biotechnology Letters
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• v.29 no.3
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• pp.155-161
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• 2001

A bactriocin produced by Lactrococcus sp. HY449 was purified by sequential purfication steps such as n-propanol-acetone precipitation ion -exchange chromatography using CM-Sequential CL6B. gel filtration chromatography using Sephacry HR100 and reverse-phase chromatography using pro RPC HR 5/10. Reverse-phase chromatography the final step of the purfication yielded a single symmetrical peak of bacteriocin activity The purification resulted in final yield of 3.25% and 413.35 fold increase of the specific activity of bacteriocin. The active fraction from reverse-phase chromatography was used for N-terminal amino acid analysis . The purified bacteriocin contained isoleucine, leucine, methionine, and glycine at but N-terminal end no aromatic amino acids. Calculation of the number of amino acid residues in the bacteriocin revealed that it is consisted of 32 residues assuming the molecular weight of bacteriocin to be about 3.6kDa. Edman degrandation elucidated amino acid residues of the first four of the N-terminus to be $NH_2$-Ile-Leu-Pro-GIn.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1052-1056
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• 2004

A secretion signal sequence-selection vector (pGS40) was constructed based on an $\alpha$-amylase gene lacking a secretion signal and employed for selecting secretion signals from Lactococcus lactis ssp. cremoris LM0230 chromosomal DNA. Six fragments were identified based on their ability to restore $\alpha$-amylase secretion in E. coli, and among these, a fragment, S405, conferred the highest secretion activity (84%) in E. coli. Meanwhile, S407, which conferred poor secretion activity in E. coli, was quite active in L. lactis. The results suggested that the efficiency of a secretion signal depended on the host. All six fragments had an open reading frame (ORF) fused to the reporter gene, and the potential Shine-Dalgamo (SD) sequence and putative promoter sequences were located upstream of the ORF. Deduced amino acid sequences from the six fragments did not show any homology with known secretion signals. However, they contained three distinguished structural features and cleavage sites, commonly found among typical secretion signals. The characterized secretion signals could be useful for the construction of food-grade secretion vectors and gene expression in LAB.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1152-1157
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• 2005

The effect of carbon sources on nisin Z biosynthesis in Lactococcus lactis subsp. lactis A164 was studied in batch culture using M17 broth containing different carbon sources. Among the eleven carbon sources tested, glucose, sucrose, and lactose were suitable carbon sources for cell growth of L. lactis A164. In particular, cells grown on lactose produced at least 3-fold greater amount of nisin Z than those on other carbon sources. Galactose resulted in less amount of cell mass than did sucrose or glucose, but gave a higher level of nisin Z activity. Northern blot analysis revealed. that lactose increased the transcription of the nisZ pre-peptide gene. Although galactose was less efficient than lactose, it increased the transcription of nisZ along with a higher level of nisin Z than did sucrose and glucose. These results suggest that the increased nisin Z production is correlated with the induction of nisZ by lactose and galactose. Among all the carbon sources tested, no remarkable differences were observed in nisRK and nisFEG transcripts, indicating that the lactose- or galactose-mediated induction is unique to the nisZ promoter.

• Journal of Microbiology and Biotechnology
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• v.16 no.11
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• pp.1799-1808
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• 2006

A food-grade integration vector based on site-specific recombination was constructed. The 5.7-kb vector, pIMA20, contained an integrase gene and a phage attachment site originating from bacteriophage A2, with the ${\alpha}$-galactosidase gene from Lactobacillus plantarum KCTC 3104 as a selection marker. pIMA20 was also equipped with a controllable promoter of nisA ($P_{nisA}$) and a signal peptide-encoding sequence of usp45 ($SP_{usp45}$) for the production and secretion of foreign proteins. pIMA20 and its derivatives mediated site-specific integration into the attB-like site on the Lactococcus lactis NZ9800 chromosome. The vector-integrated recombinant lactococci were easily detected by the appearance of blue colonies on a medium containing $X-{\alpha}-gal$ and also by their ability to grow on a medium containing melibiose as the sole carbon source. Recombinant lactococci maintained these traits in the absence of selection pressure during 100 generations. The ${\alpha}-amylase$ gene from Bacillus licheniformis, lacking a signal peptide-encoding. sequence, was inserted downstream of $P_{nisA}\;and\;SP_{usp45}$ in pIMA20, and the plasmid was integrated into the L. lactis chromosome. ${\alpha}-Amylase$ was successfully produced and secreted by the recombinant L. lactis, controlled by the addition and concentration of nisin.

• Journal of Microbiology and Biotechnology
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• v.9 no.2
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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.

• Food Science of Animal Resources
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• v.37 no.3
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• pp.402-409
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• 2017

A novel peptide having free radical scavenging activity was separated, using an on-line high-performance liquid chromatography (HPLC) - ABTS screening method, from bovine skim milk fermented by Lactococcus lactis SL6 (KCTC 11865BP). It was further purified using reverse phase-HPLC (RP-HPLC) and sequenced by RP-HPLC-tandem mass spectrometry. The amino acid sequence of the identified peptide was determined to be Phe-Ser-Asp-Ile-Pro-Asn-Pro-Ile-Gly-Ser-Glu-Asn-Ser-Glu-Lys-Thr-Thr-Met-Pro-Leu-Trp (2,362 Da), which is corresponding to the C-terminal fragment of bovine ${\alpha}_{s1}$-casein (f179-199). The hydroxyl radicals scavenging activity ($IC_{50}$ $28.25{\pm}0.96{\mu}M$) of the peptide chemically synthesized based on the MS/MS data showed a slightly lower than that of the natural antioxidant Trolox ($IC_{50}$ $15.37{\pm}0.52{\mu}M$). Furthermore, derivatives of the antioxidant peptide were synthesized. The antioxidative activity of the derivatives whose all three proline residues replaced by alanine significantly decreased, whereas replacement of two proline residues in N-terminal region did not affect its antioxidative activity, indicating that $3^{rd}$ proline in C-terminal region is critical for the antioxidative activity of the peptide identified in this study. In addition, N-terminal region of the antioxidant peptide did not show its activity, whereas C-terminal region maintained antioxidative activity, suggesting that C-terminal region of the peptide is important for antioxidative activity.

• Journal of fish pathology
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• v.11 no.2
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• pp.137-141
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• 1998

Temperate phages were effectively induced from presumptive lysogenized cells of 96 strains out of 111 strains of L. garvieae No. 44 strains (phage type B) as the host cell. Similar cultures in distilled water-based TSB did not induce lytic infection in these cells. These temperate phages were also effectively induced by ultraviolet irradiation. All phages isolated were lytic only to L. garvieae No. 44 strain and the lytic nature was different from those of PLgY, PLgW, and PLgS. The virions appeared extracellularly after 1h of induction culture and increased in number until reaching the maximum of $10^6$ PFU/ml after 12h. This phage production was lower than that ($10^{10}$ PFU/ml) of the virulent phage.

• Food Science of Animal Resources
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• v.40 no.2
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• pp.155-171
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• 2020

Fermented products, including sausages, provide several health benefits, particularly when probiotics are used in the fermentation process. This study aimed to examine the cytotoxicity (against Caco-2 and MCF-7 cell lines), antihypertensive activity via angiotensin-converting enzyme (ACE) inhibition, antioxidant capacity, antidiabetic activity via α-amylase and α-glucosidase inhibition, proteolysis rate, and oxidative degradation of fermented camel and beef sausages in vitro by the novel probiotic Lactococcus lactis KX881782 isolated from camel milk. Moreover, camel and beef sausages fermented with commercial starter culture alone were compared to those fermented with commercial starter culture combined with L. lactis. The degree of hydrolysis, antioxidant capacity, cytotoxicity against Caco-2 and MCF-7, α-amylase, α-glucosidase, and ACE inhibitory activities were higher (p<0.05) in fermented camel sausages than beef sausages. In contrast, the water and lipid peroxidation activity were lower (p<0.05) in camel sausages than beef sausages. L. lactis enhanced the health benefits of the fermented camel sausages. These results suggest that camel sausage fermented with the novel probiotic L. lactis KX881782 could be a promising functional food that relatively provides several health benefits to consumers compared with fermented beef sausage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.8
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• pp.1066-1071
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• 2012

In this study we investigated the change in antigenicity and allergenicity of Meju, a traditional Korean soybean product, by fermentation via 3 different microorganisms. The steamed soybeans were fermented with Lactococcus lactis subsp. lactis and/or Aspergillus oryzae and/or Bacillus subtilis. Proteins in soybean were degraded after fermentation. Antigenicity or allergenicity were analysed by immunoblotting and ELISA using soybean protein-specific polyclonal antibodies or soybean allergic patient sera. The best degradation was achieved by three step fermentation using nisin-producing Lactococcus lactis subsp. lactis IFO12007, A. oryzae and B. subtilis. Allergenicity and antigenicity were also starkly reduced after three step fermentation. The three-step fermentation method developed in our lab suggests an excellent alternative to reduce the allergenicity of soybeans.