• Microbiology and Biotechnology Letters
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• v.44 no.1
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• pp.26-33
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• 2016

Dominant lactic acid bacteria (LAB) strains were isolated from traditional fermented foods to obtain rare ${\gamma}$-aminobutyric acid (GABA)-producing LAB. Out of 147 isolates, 23 strains that could produce GABA with 1% (w/v) L-monosodium glutamate (MSG) were first isolated. After further screening of these rare GABA-producing LAB by analysis of the glutamate decarboxylase and 16S rRNA gene sequences, Enterococcus faecium JK29 was isolated, and 1.56 mM of GABA was produced after 48 h cultivation in basic de Man, Rogosa, and Sharpe (MRS) medium. To enhance GABA production by E. faecium JK29, the culture conditions were optimized. When E. faecium JK29 was cultivated in optimized MRS medium containing 0.5% (w/v) sucrose and 2% (w/v) yeast extract with 0.5% (w/v) MSG, GABA production reached 14.86 mM after 48 h cultivation at initial conditions of pH 7.5 and $30^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.40 no.4
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• pp.389-395
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• 2012

T-RFLP (terminal restriction fragment length polymorphism) analysis, one of the most highly adopted culture-independent microbial community analysis methods, was applied to evaluate the colonization of probiotics in experimental animal gut. Lactic acid bacteria that exhibited cinnamoyl esterase activity were isolated from Korean fermented vegetables and identified by 16S ribosomal RNA sequence analysis. Lactobacillus plantarum KK3, which demonstrated high chlorogenic acid hydrolysis by cinnamoyl esterase activity, and acid/bile salt resistances, was cultured, freeze-dried, and fed to mice and the microbiota in their feces were monitored by T-RFLP analysis. The T-RF of L. plantarum was detected in the feces of mice after the start of administration and lasted at least 31 days after the initial 7 day feeding. T-RFLP analysis was considered a useful tool to evaluate the gut colonization of probiotic L. plantarum. In order to prove that L. plantarum was from viable cells, we reisolated L. plantarum in the feces using cinnamoyl esterase activity media as the screening step. The colonization of L. plantarum KK3 in the mouse gut was confirmed by this research.

• Microbiology and Biotechnology Letters
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• v.36 no.2
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• pp.121-127
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• 2008

A strain IDCC 9203 isolated from infant feces was identified as Lactobacillus johnsonii on the basis of 16S rDNA sequence analysis. L. johnsonii IDCC 9203 was highly resistant to acid (MRS broth at pH 2.3) and bile (MRS broth with 0.3% oxgall). The antibacterial activities of L. johnsonii IDCC 9203 was examined against Salmonella typhimurium KCTC 2054. The growth of S. typhimurium KCTC 2054 was inhibited by the cell-free culture supernatant (at pH 4.0) of L. johnsonii IDCC 9203 as well as by the respective control (MRS broth at pH 4.0). Antimicrobial effect against S. typhimurium KCTC 2054 of L. johnsonii IDCC 9203 was probably due to the lactic acid. By an in vitro cell adhesion model, L. johnsonii IDCC 9203 preincubated or coincubated with Caco-2 cells reduced the adhesion of S. typhimurium KCTC 2054 to Caco-2 cells by 74% or 47.1%, respectively. Also in an in vivo model, L. johnsonii IDCC 9203 was colonized in mice intestines which were disrupted by ampicillin treatment. Its proliferation in the mice intestines reduced abnormal salmonella growth from $10^9CFU/g$ feces to $10^5CFU/g$ feces as an indigenous level. The results obtained in this study suggest that L. johnsonii IDCC 9203 may be a potential probiotic strain.

• Journal of Microbiology and Biotechnology
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• v.27 no.5
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• pp.925-932
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• 2017

Changes in the metabolite profiles of Lactobacillus sakei and its growth media, based on different culture times (0, 6, 12, and 24 h), were investigated using gas chromatography-mass spectrometry (MS) and liquid chromatography-MS with partial least squares discriminant analysis, in order to understand the growth characteristics of this organism. Cell and media samples of L. sakei were significantly separated on PLS-DA score plots. Cell and media metabolites, including sugars, amino acids, and organic acids, were identified as major metabolites contributing to the difference among samples. The alteration of cell and media metabolites during cell growth was strongly associated with energy production. Glucose, fructose, carnitine, tryptophan, and malic acid in the growth media were used as primary energy sources during the initial growth stage, but after the exhaustion of these energy sources, L. sakei could utilize other sources such as trehalose, citric acid, and lysine in the cell. The change in the levels of these energy sources was inversely similar to the energy production, especially ATP. Based on these identified metabolites, the metabolomic pathway associated with energy production through lactic acid fermentation was proposed. Although further studies are required, these results suggest that MS-based metabolomic analysis might be a useful tool for understanding the growth characteristics of L. sakei, the most important bacterium associated with meat and vegetable fermentation, during growth.

• Food Science and Preservation
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• v.23 no.3
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• pp.326-334
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• 2016

Omija (Schizandra chinensis) extract (OE) was fermented by using Lactobacillus plantarum EJ2014 to produce a beverage fortified with gamma-aminobutyric acid (GABA). After 2 days of fermentation in the presence of 2% monosodium glutamate (MSG) and 0.5% yeast extract (YE), the four-fold-diluted OE showed a higher viable cell count ($2.2{\times}10^9CFU/mL$) and lower acidity (1.2%) than that of the unfermented OE. In particular, addition of MSG as a precursor resulted in a small increase in the initial pH. MSG (2%) was completely converted to GABA (0.92%) during lactic acid bacteria fermentation for 3 days. Furthermore, the acidity of the fermented OE decreased from 1.74% to 0.56%. In addition, the original red color of the OE disappeared during LAB fermentation. However, when the fermented OE was mixed with 50% of the original OE, the original red color was recovered, with 19.56 and 13.92 for Hunter L and a values, respectively. The mixture of 50% original OE and 50% fermented OE showed the highest sensory score including the highest overall preference. In conclusion, the OE fortified with GABA and probiotics was produced by fermentation with a static culture, L. plantarum EJ2014.

• Food Science of Animal Resources
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• v.29 no.1
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• pp.15-23
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• 2009

In order to develop a new starter for fermented milk, 2082 bacteria were isolated from raw milk. The strain that showed excellent acid forming and ${\gamma}$-aminobutyric acid (GABA) production ($711.40{\mu}g/g$ D.W) characteristics after incubation at $37^{\circ}C$ for 18 hr was selected and identified as Lactobacillus acidophilus by the result of API carbohydrate fermentation pattern and 16S rDNA sequence. L. acidophilus RMK567 was investigated for its physiological characteristics. RMK67 strain showed good GABA production compared with commercial lactic acid bacteria. The optimum growth temperature of L. acidophilus RMK567 was $40^{\circ}C$ and cultures took 15 hr to reach pH 4.3. L. acidophilus RMK567 showed higher sensitivity to penicillin-G, novobiocin, as compared to other 14 different antibiotics. However, it showed more resistance to kanamycin, neomycin, streptomycin. It showed higher leucine arylamidase and ${\beta}$-galactosidase activities compared to 16 other enzymes. It was comparatively tolerant to bile juice and able to survive at pH 2 for 3 hr. It showed resistence to Escherichia coli, Salmonella typhimurium and Staphylococcus aureus with rates of 29.2%, 39.1% and 51.4%, respectively. Based on these and previous results, L. acidophilus RMK567 could be an excellent starter culture for fermented milk with excellent GABA contents.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.12
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• pp.1798-1807
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• 2002

This study was conducted to investigate lactobacillus salivarius subsp. salivarius having probiotic properties to be used as the health adjuncts with fermented milk products. Acid- and bile-tolerant lactobacillus salivarius subsp. salivarius was isolated with lactobacilli MRS broth from faeces of 80 healthy persons (infants, children and adults). It was used as a probiotic strain in fermented milk products. The pH of fermented milk decreased from pH 6.7 to 5.0 and titratable acidity increased from 0.3% to 1.0% by L. salivarius subsp. salivarius (isolation strain 20, 35, and 37), when incubated for 36 h at 37$^{\circ}C$. The number of viable cell counts of fermented milk was maximized at this incubation condition. The SDS-PAGE evidenced no significant change of casein but distinct changes of whey protein were observed by isolated L. salivarius subsp. salivarius for titratable acidity being incubated by 0.9-1.0% at 37$^{\circ}C$. All of the strains produced 83.43 to 131.96 mM of lactic acid and 5.39 to 26.85 mM of isobutyric acid in fermented products. The in vitro culture experiment was performed to evaluate ability to reduce cholesterol levels and antimicrobial activity in the growth medium. The selected L. salivarius subsp. salivarius reduced 23-38% of cholesterol content in lactobacilli MRS broth during bacterial growth for 24 h at 37$^{\circ}C$. All of the isolated L. salivarius subsp. salivarius had an excellent antibacterial activity with 15-25 mm of inhibition zone to E. coli KCTC1039, S. enteritidis KCCM3313, S. typhimurium M-15, and S. typhimurium KCCM40253 when its pH had not been adjusted. Also, all of the isolated L. salivarius subsp. salivarius had partial inhibition zone to E. coli KCTC1039, E. coli KCTC0115 and S. enteritidis KCCM3313 when it had been adjusted to pH 5.7. The selected strains were determined to have resistances of twelve antibiotic. Strains 27 and 35 among the L. salivarius subsp. salivarius showed the highest resistance to the antibiotics. These results indicated that some of the L. salivarius subsp. salivarius (strain 27 and 35) are considered as effective probiotic strains with a potential for industrial applications, but the further study is needed to establish their use as probiotics in vivo.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.205-210
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• 1983

Extracellular $\beta$-galactosidase was prepared from a culture of Lactobacillus sporogenes, a spore-forming lactic acid bacterium. The enzyme functioned optimally at pH 6.8 and at 6$0^{\circ}C$ o-nitrophenyl-$\beta$-D-galactopyranoside (ONPG) in 0.05M sodium phosphate buffer. The activation energy of the enzymatic hydrolysis of ONPG was about 16,000 cal/mole below $50^{\circ}C$ and 11,300 cal/mole above the temperature. It was fairly stable over a pH range from 4.0 to 8.0 losing only less than 30% of its activity after hearting at 6$0^{\circ}C$ and pH 6.8 for 3 hours. Metal ions showed no significant effect on the enzyme activity, whereas L-cysteine exerted a slight stimulatory effect at the concentration of 10mM. The km values were 1.48mM for ONPG and 64.5mM for lactose. Hydrolysis of ONPG by the enzyme was product-inhibited by galactose (Ki=13.3mM, competitive inhibition) and by glucose(Ki= 11.4mM, uncompetitive type). The enzyme activity was also noncompetitively inhibited in the presence of lactose (Ki= 17.8mM).

• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.311-318
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• 2002

A new bacteriocin producing lactic acid bacteria having antagonistic activity against Lactobacillus plantarum, was isolated from Kimchi. It was identified as Leuconostoc mesenteroides, and designated as Leuconostoc mesenteroides B7. The bacteriocin from Leuconostoc mesenteroides B7 named as bacteriocin B7 was stable in the pH range $2.5{\sim}9.5$. Bacteriocin B7 was active over a wide temperature range from $4^{\circ}C$ to $120^{\circ}C$. It was inactivated by proteinase K, trypsin, ${\alpha}-chymotrypsin$, and protease treatments indicating its proteinous nature. Tricine-SDS-PAGE of the purified bacteriocin B7 showed the presence of a single band, having a molecular mass of about 3,500 dalton. Mixed culture of the producer and the indicator, Lb. plantarum KFRI 464 or Lb. delbruekii KFRI 347, increased production of bacteriocin B7. This result suggested the presence of bacteriocin inducing factor in the indicator strain. The inducing factor was localized in cell debris and intracellular faction of the indicator cell, Lb. plantarum KFRI 464. Treatment of the inducing factor with proteinase K destroyed inducing activity. This result strongly suggested that the inducing factor is a protein.

• Food Science and Preservation
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• v.22 no.6
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• pp.851-858
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• 2015

This study was designed to improve the sensory characteristics and mitigate the bitter taste of Platycodon gradiflorum. It was aimed at investigating the qualitative properties of fermented P. gradiflorum after repeated steaming and drying treatments. P. gradiflorum was heated for 2 hr at $95^{\circ}C$, being the first and third treatments compared afterwards. Lactobacillus plantarum, at a concentration of 10%, was used as starter culture. As a result, the third steaming process and the addition of starter improved the physical and chemical properties of P. gradiflorum i.e., crude saponin and total polyphenol contents increased significantly. Moreover, P. gradiflorum steamed three times and fermented by L. plantarum showed the higher overall preference score. Our results indicated that the three-time steaming and drying was an effective manufacturing process for the production of high-quality fermented P. gradiflorum. Lactic acid-fermented P. gradiflorum also could have a potential use as a valuable resource for the development of functional products.