• Food Science of Animal Resources
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• v.42 no.6
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• pp.1009-1019
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• 2022

In recent years, biocontrol of foodborne pathogens has become a concern in the food industry, owing to safety issues. Listeria monocytogenes is one of the foodborne pathogens that causes listeriosis. The major concern in the control of L. monocytogenes is its viability as it can survive in a wide range of environments. The purpose of this study was to isolate lactic acid bacteria with antimicrobial activity, evaluate their applicability as a cheese starter, and evaluate their inhibitory effects on L. monocytogenes. Lactococcus lactis strain with antibacterial activity was isolated from raw milk. The isolated strain was a low acidifier, making it a suitable candidate as an adjunct starter culture. The commercial starter culture TCC-3 was used as a primary starter in this study. Fresh cheese was produced using TCC-3 and L. lactis CAU2013 at a laboratory scale. Growth of L. monocytogenes (5 Log CFU/g) in the cheese inoculated with it was monitored during the storage at 4℃ and 10℃ for 5 days. The count of L. monocytogenes was 1 Log unit lower in the cheese produced using the lactic acid bacteria strain compared to that in the cheese produced using the commercial starter. The use of bacteriocin-producing lactic acid bacteria as a starter culture efficiently inhibited the growth of L. monocytogenes. Therefore, L. lactis can be used as a protective adjunct starter culture for cheese production and can improve the safety of the product leading to an increase in its shelf-life.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.823-830
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• 2023

Lactococcus lactis is a lactic acid bacterium and used in the dairy food industry. The ameliorating effects of Lactobacillus species on atopic dermatitis (AD) have been extensively studied, but the specific effect of L. lactis strains has not yet been investigated. In this study, the efficacy of L. lactis LB 1022, isolated from natural cheese, was evaluated using RAW 264.7, HMC-1 and HaCaT cell lines and an ovalbumin-sensitized AD mouse model. L. lactis LB 1022 exhibited nitric oxide suppression and anti-allergy and anti-inflammatory activity in vitro. Oral administration of L. lactis LB 1022 to AD mice significantly reduced the levels of IgE, mast cells, and eosinophils, and a range of T cell-mediated T helper Th1, Th2, and Th17-type cytokines under interleukin (IL)-10, transforming growth factor-β (TGF-β), thymus and activation-regulated chemokine (TARC), and thymic stromal lymphopoietin (TSLP). In addition, L. lactis LB 1022 treatment increased the concentration of short-chain fatty acids. Overall, L. lactis LB 1022 significantly modulated AD-like symptoms by altering metabolites and the immune response, illustrating its potential as candidate for use in functional food supplements to alleviate AD.

• Journal of Animal Science and Technology
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• v.65 no.3
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• pp.679-682
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• 2023

The Lactococcus taiwanensis strain K_LL004 was isolated from the gut of a grasshopper (Oxya chinensis sinuosa) collected from local farm in Korea. L. taiwanensis strain K_LL004 is the functional probiotic candidate with an ability to hydrolyse plant polysaccharides. The complete genome of the L. taiwanensis strain K_LL004 contains one circular chromosome (1,995,099 bp) with a guanine + cytosine (GC) content of 38.8%. Moreover, 1,929 Protein-coding sequence, 19 rRNA genes, and 62 tRNA genes were identified based on results of annotation. L. taiwanensis strain K_LL004 has a gene, which encodes hydrolytic enzymes such as beta-glucosidase and beta-xylosidase, that hydrolyzes plant polysaccharides.

• Journal of Dairy Science and Biotechnology
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• v.41 no.3
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• pp.138-148
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• 2023

In this study, Lactococcus lactis subsp. hordniae JNU533 (JNU533) was isolated from Swiss-type cheese, and the bacteriocin produced by this strain was characterized. The spot-on-lawn assay was used to determine the antimicrobial spectrum and characteristics of the JNU533-derived bacteriocin. Results confirmed that the JNU533-derived bacteriocin inhibited the growth of lactic acid bacteria. The size of the bacteriocin was approximately 4.9 kDa, and it was heat- and pH-stable under various temperature and pH conditions. Furthermore, the possibility of using JNU533 as a starter culture in the manufacturing of fermented dairy products was assessed. A single colony of JNU533 was inoculated into 10% skim milk containing 0.5% glucose to investigate its characteristics in milk culture. The decrease in the pH was similar to that elicited by Lactobacillus delbrueckii subsp. bulgaricus. Furthermore, the results confirmed that JNU533 inhibited the growth of various bacteria and could be used as a milk fermentation starter. This study highlights the characteristics of the bacteriocin produced by JNU533 and the growth features of this strain in a skim milk medium.

• Korean Journal of Microbiology
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• v.47 no.1
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• pp.74-80
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• 2011

Bacteriocin-producing lactic acid bacterium having antagonistic activity against Bacillus cereus, was isolated from Kimchi. The selected strain was identified as Lactococcus lactis by the Bergey's manual and 16S rDNA analysis, and named as L. lactis ET45. The bacteriocin was stable in the pH range 3.0-11.0. The bacteriocin was active over a wide temperature range from $40^{\circ}C$ to $121^{\circ}C$. Optimal culture condition for producing bacteriocin was obtained by growing the cells on MRS medium at pH 7.5 and $30^{\circ}C$ for 18 h. Antibacterial activity of the bacteriocin was completely disappeared by proteinase K, and this means that bacteriocin is a proteinous substance. The molecular weight of bacteriocin was estimated to be about 4.5 kDa by tricine sodium dodecyl sulfate polyacryamide gel electrophoresis (TSDS-PAGE).

• 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.

• Journal of fish pathology
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• v.14 no.2
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• pp.71-80
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• 2001

The purpose of this study was to investigate the microbiological characteristics and the distributions of the bacteria causing streptococcicosis occurred in marine fish farm, Korea. Many kinds of cultures fishes suffered from the disease accompanied with typical symptoms, including darkening of the skin, exophthalmia, petechiae inside of the opercula and distended abdomen. The isolates from the diseased fishes were compared with Lactococcus garvieae by biochmical, biophysical and serological methods and polymerase chain reaction(PCR) assay. We isolated 35 strains of the geuns Streptococcus from the diseased olive flounder, Paralichthys olivaceus, yellow tail, Seriola quinqueradiata and Korean rockfish, Sebastes schlegeli. 15 strains out of the isolates were identified to L. garvieae and the others were not because of their different biochemical and biophysical charateristics. Seven strains of the isolates were agglutinated by rabbit serum raised against L. garvieae $KG^+$ phenotypic cells(ATCC49156)as a reference strain. Twenty-one strains of the isolates identified to L. garvieae since they were formed the expected band through performing PCR assay using specific primers, pLG-1(5'-CATAACAATGAGATCGC-3') and pLG-2(5'-GCACCCCGCGGTTG-3'). In the present study, it showed that L. garvieae was a dominant strain causing streptococcicosis in the tested area due to occurrence of 21 strains as L. garvieae out of all the isolates, 9 atrains as Streptococcus sp. and 5 strains as Enterococcus sp.

• 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.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.21-34
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• 2021

Chitosan nanoparticles (CNPs) and Lactococcus lactis (L. lac.) were used as adsorbents to evaluate the adsorption performance of endocrine hormones, which are phthalates, in the healthy food packages. CNPs were produced through the cross bond with tripolyphosphate (TPP), and L. lac.-CNPs were prepared through the introduction of L. lac. during the preparation. The various functional groups of all adsorbents were identified using Fourier transform infrared spectroscopy (FTIR). Adsorption isotherm and adsorption kinetic confirmed the adsorption behavior and mechanism of CNPs, L. lac. and L. lac.-CNPs. The adsorption behavior of DBP and DEP for all particles was more suitable for the Freundlich adsorption isotherm model than for the Langmuir adsorption isotherm model, which means that the surface of the particles is heterogeneous. The adsorption mechanism was more suitable for the Pseudo-2nd-order model than for the Pseudo-1st-order model. This means that due to the presence of various functional groups on the particle surface, the adsorption of DBP and DEP is dominated by chemical adsorption such as electrostatic attraction and hydrogen bonding rather than physical adsorption. Finally, it was confirmed that the preparation of CNPs and L. lac.-CNPs can be performed easily and quickly, and it could be used as a cheaper adsorbent that can effectively remove phthalates.

• 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.