• Journal of Microbiology and Biotechnology
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• 제9권3호
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• pp.282-291
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• 1999

Lactic acid bacteria were isolated from Kimchi and screened for bacteriocin. A total of 99 strains showed antimicrobial activity when grown on solid media, yet only 10 showed antimicrobial activity in liquid media. Strain H-559, identified as Lactococcus lactis subsp. lactis, exhibited the strongest inhibitory activity and was active against pathogenic bacteria including Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus as well as other lactic acid bacteria. The antimicrobial substance produced by L. lactis subsp. lactis H-559 was confirmed to be a bacteriocin by the treatment of $\alpha$-chymotrypsin, and protease type Ⅸ and ⅩIV. The bacteriocin activity remained stable between pH 2.0 and pH 11.0 and during heating for 10 min at $100^{\circ}C$. The bacteriocin production started in the exponential phase and stopped in the stationary phase. L. lactis subsp. lactis H-559 showed the highest bacteriocin activity at a culture temperature of $25^{\circ}C$, and an inverse relationship between the bacteriocin productivity and mean growth rate at different culture temperatures was observed. The mean growth rate and bacteriocin productivity of L. lactis subsp. lactis H-559 increased as the initial pH of the media increased.

• Journal of Dairy Science and Biotechnology
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• 제41권3호
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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.

• 생명과학회지
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• 제6권1호
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• pp.27-33
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• 1996

치즈숙성과정 중에서 Lactococcus lactis subsp. cremoris KH (lac$^{+}$ prt$^{+}$ ) and KHA (lac$^{-}$ prt$^{-}$ )의 혼합균에 의하여 일어나는 반응을 연구하였다. 혼합균의 성장 특징은 한쪽 균의 도움에 의하여 같이 성장하는 특징을 나타내었으며, 이 혼합균의 단백질분해효소의 양은 충분히 적었다. 이 결과로부터 치즈숙성과정 중에 홈합균의 균밀도가 높게 유지되더라도, 이 혼합균에 의하여 생성되는 쓴 맛의 생성량은 큰 문제가 되지 않는다는 결론을 얻을 수 있다. 그러므로, 치즈 숙성 과정을 촉진시키는데 있어서 KHA1의 혼합균은 좋은 치즈스타터균의 하나라고 할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제4권4호
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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.

• 한국미생물·생명공학회지
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• 제22권3호
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• pp.240-245
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• 1994

Relation the phage defense mechanism of phage resistant Lactococcus lactis subsp. cremoris ATCC 11602-A1 to its cell wall components was investigated. To determine whether teichoic acid which is known to be one of the phage receptor site present on the cell wall, phage adsorption was examined after treatment 5% TCA(60%$\CIRC $C) and concanavalin A to the cell wall of A1 and parent strain. However, the adsorption rate of two strains did not change. Total amount of phosphate after TCA treatment did not change in both strains, but a difference between the two strains was observed. Ribitol and glycerol, components of teichoic acid, could not be detected in the cell walls of two strains by GC analysis. These results suggest that although teichoic acid was not present in the cell walls of both strains, the composition of cell wall of two strains was not identical. Measurement of amount of protein and SDS-polyacryamide gel electrophoresis were carried out to examine the involvement of cell wall protein in phage resistance, showing that protein is nothing to do with phage adsorption of parent strain, but phage resistance of A1 is related to protein. Cell wall carbohydrates of A1 contained rhamnose, glucose, and galactose. Total amount of carbohydrate of 1% SDS-treated A1 cell wall was reduced to the level of parent strain. The results suggest that phage resistance of A1 was due to the presence of a higher level of carbohydrates then parent strain, and to interaction of carbohydrate and protein.

• Journal of Microbiology and Biotechnology
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• 제4권3호
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• pp.191-194
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• 1994

Acetoin and ammonia, the precursors of tetramethylpyrazine (TMP) having "nutty " or "roasted" flavors, were produced by cultivating Lactococcus lactis ssp. lactis biovar. diacetilactis FC1. The effects of the volume concentration ratio (VCR) of cell-free medium on the formation of TMP were investigated using a rotary evaporator at $70^{\circ}C than at 80^{\circ}C$. As the VCR increased, the formation of TMP and the conversion ratio of acetoin to TMP increased. More TMP were formed at $70^{\circ}C than at 80^{\circ}C$. As the VCR increased, the concentration of acetoin decreased implying the formation of TMP from acetoin and ammonia.

• Journal of Microbiology and Biotechnology
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• 제3권4호
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• pp.217-223
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• 1993

To investigate the nature and location of the nisin-resistance determinant of Lactococcus lactis subsp. lactis 7962 (L. lactis 7962), a total plasmid DNA prepared from L. lactis 7962, a nisin producer, was used to transform L. lactis subsp. lactis LM0230, a plasmid-free and nisin-sensitive strain, by protoplast mediated transformation procedures. All of the nisin-resistant transformants acquired the ability to utilize sucrose at the same time, confirming the close linkage between these two determinants in L. lactis 7962. The plasmid DNA profiles of a few selected nisin-resistant transformants were examined by agarose gel electrophoresis. No common plasmid was found among the transformants and some small plasmids previously not present in L. lactis 7962 were detected. These transformants were named as L. lactis KL1, KL2, KL3, KL4, or KL5, respectively based on their plasmid profiles. Growth curves of all transformants were similar to that of L. lactis LM0230, but different from that of L. lactis 7962. L. lactis KL5 showed the highest level of resistance to nisin, growing up to 1, 200 IU nisin/ml after 40 hr incubation. Some nisin-sensitive derivatives of KL1 or KL2 were obtained by plasmid curing experiments. The plasmid DNA profiles of the nisin-sensitive KL1 derivatives were apparently the same as that of the KL1. All of the nisin-sensitive KL2 derivatives were plasmid-free, but a nisin-resistant strain with no apparent plasmid was also obtained. These results indicate that the nisin-resistance of the $Nis^r$ transformants is presumably mediated by the chromosomally located gene(s) rather than plasmid-encoded gene(s).

• 한국식품영양학회지
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• 제14권1호
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• pp.59-64
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• 2001

돼지고기 등심의 표면에 Lactococcus lactis subsp. Jactis ATCC l1454 유산균 배양액 3.96 log units의 처리구는 4$^{\circ}C$ 저장 1일 이후 대조구의 TBA가와 유의적 차이가 없었다 (P>0.05). 유산균 배양액 3.96 log units 처리구의 Hunter color L*과 b*가는 저장 동안 대조구와 유의적 차이가 없었다. 그러나 유산균 배양액 4.10과 4.23 log units 처리구의 Hunter a*가는 4$^{\circ}C$ 저장 1일과 6일 이후 대조구와 유의적 차이 (P<0.05)를 나타내었다. 유산균 배양액 4.10과 4.23 log units 처리구의 육즙유출율은 4$^{\circ}C$ 저장 4일 이후부터 처리구와 대조구 사이에 유의적 차이를 나타내었다.

• Asian-Australasian Journal of Animal Sciences
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• 제17권12호
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• pp.1741-1745
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• 2004

Administration of milk and fermented milks produced from indigenous dadih lactic acid bacteria on serum lipids and bile acids, fecal bile acids and microflora was estimated in hypercholesterolemic rats. Anaerobic lactic acid bacteria decreased and coliforms increased in the feces of the control group; however, the number of fecal lactic acid bacteria remained unchanged when rats were administered milk and fermented milks. Only fermented milk made from Lc. lactis subsp. lactis IS-10285 significantly reduced serum total cholesterol, LDL cholesterol and total bile acids. Milk and fermented milks did not influence the HDL cholesterol. Triglyceride and phospholipid levels were significantly lower in the rats fed fermented milk of Lc. lactis subsp. lactis IS-10285 than rats fed milk and fermented milk of Lc. lactis subsp. lactis IS-29862, but not significantly different from the control group. Hypocholesterolemic effect of Lc. lactis subsp. lactis IS-10285 was attributed to its ability to suppress the reabsorption of bile acids into the enterohepatic circulation and to enhance the excretion of bile acids in feces of hypercholesterolemic rats.

• Journal of Dairy Science and Biotechnology
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• 제37권2호
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• pp.129-135
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• 2019

This study investigated the effects of heat-treated and non-heat-treated bovine lactoferrin on the growth of Lactococcus lactis subsp. cremoris JCM 20076. The addition of heat-treated and non-heat-treated bovine lactoferrin in adjusted MRS medium stimulated the growth of Lc. cremoris JCM 20076. Heat-treated bovine lactoferrin had a greater impact on the growth of Lc. cremoris JCM 20076 compared to that with non-heat-treated bovine lactoferrin. Bovine lactoferrin heated at $65^{\circ}C$ for 30 min stimulated the growth of the bacteria more than that heated at $80^{\circ}C$ for 5 min. Furthermore, the growth of Lc. cremoris JCM 20076 increased substantially with heat-treated bovine lactoferrin at a concentration of 1 mg/mL.