• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.1221-1224
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• 2007

현재 기업들 간의 전화비를 줄이고 각종 VoIP 부가 서비스를 위해 VoIP 시스템의 도입이 시작 되었다. 이에 VoIP 전화기들 간의 각 기능을 최대한 활용하기 위해 현재 VoIP 시장의 90%를 차지하고 있는 H.323 게이트웨이(Gateway)간의 H.323 프로토콜의 구현차이로 인한 문제점이 발생되기 시작되었다. 본 논문은 VoIP Gateway상에 H.323 프로토콜 통신을 하면서 프로토콜 연결 상 구현의 차이로 인해 VoIP 서비스에 비정상적인 작동으로 호가 종료가 되거나 음성이 들리지 않는 현상 및 전화기의 부가서비스를 사용할 수 없는 문제를 해결하기 위해 H.323 프로토콜의 작동을 분석하고 이기종간의 H.323프로토콜 신호가 호환되지 않을 경우 이를 해결하기 위해 H.323 프로토콜상의 H.245 시그널링 (signaling)을 Media gateway 서버를 이용해 구현한 RFC 2833 DTMF-compliant 프로토콜을 사용하여 H.323 프로토콜 처리함으로써 이기종간의 Call transfer, Hold 그리고 Conferenct 기능에 대한 호환성이 개선됨을 보여 준다.

• Microbiology and Biotechnology Letters
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• v.43 no.3
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• pp.219-226
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• 2015

Acetic acid bacteria (AAB) were isolated from vinegar fermented through traditional methods in Namhae county, Gyeongnam, the Republic of Korea. The isolated strains were Gram negative, non-motile, and short-rods. Three selected strains were identified as either Acetobacter pasteurianus or Acetobacter aceti by 16S rRNA gene sequencing. A. pasteurianus NH2 and A. pasteurianus NH6 utilized ethanol, glycerol, D-fructose, D-glucose, D-mannitol, D-sorbitol, L-glutamic acid and Na-acetate. A. aceti NH12 utilized ethanol, n-propanol, glycerol, D-mannitol and Na-acetate. These strains grew best at 30℃ and an initial pH of 3.4. They were tolerant against acetic acid at up to 3% of initial concentration (v/v). The optimum conditions for acetic acid production were 30℃ and pH 3.4, with an initial ethanol concentration of 5%, resulting in an acetic acid concentration of 7.3−7.7%.

• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.242-249
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• 2003

Antimicrobial activity of Caesalpina sappan L. extract (CS extract) against animal husbandry disease-related bacteria was studied. The CS extracts showed a significant antimicrobial activity against Gram(+) bacteria and this antimicrobial activity was most significant against Staphylococcus epidermidis. Minimum inhibitory concentrations (MIC) of CS was in the range of 0.8∼16 mg/ml and 0.8∼10 mg/ml, in the case of MeOH extracts and EtOH extracts, respectively. In addition, the antimicrobial activity of each solvent fraction was most significant with EtOAc layer. The antimicrobial activities of CS extracts against most microbial strains were stable by either heat treatment or acid treatment, whereas those against S. aureus and Sal. typhimurium were reduced by acid treatment. The inhibitory effect of CS extracts on microbial cell growth was further examined by the addition of 0, 100, 300, and 500 ppm of CS extracts into growth medium. The growth of gram(+) bacteria, S. aureus and S. epidermidis, was inhibited for 72 hours in all ranges of CS extracts added, but the growth of gram(-) bacteria was only inhibited when at least 100 ppm of CS extracts were added. Taken together, the antimicrobial activities of CS extracts were more effective against gram(+) bacteria compared to those against gram(-) bacteria.

• Microbiology and Biotechnology Letters
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• v.39 no.4
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• pp.390-396
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• 2011

Lactobacillus sakei is known to be the most populous lactic acid bacteria in over-ripened kimchi. Twenty three strains of Leuconostoc species inhibiting the growth of Lb. sakei were isolated from kimchi and amongst these the Leuconostoc mesenteroides strain CK0122 exhibited the highest antagonistic activity against Lb. sakei. The culture supernatant of the strain CK0122 was fractionated by a molecular weight cutter and lyophilized. The fraction with a molecular weight of less than 3,000 Da showed antagonistic activity against Lb. sakei. The antibacterial activity of the active fraction was sensitive to proteinase K treatment, confirming its proteinaceous nature (bacteriocin). The crude bacteriocin was active in the pH range of 4 to 7 and extremely stable after 15 min of heat treatment at $121^{\circ}C$. The crude bacteriocin inhibited the growth of Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Alcaligenes xylosoxydans, Flavobacterium sp., and Salmonella typhimurium.

• Microbiology and Biotechnology Letters
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• v.37 no.1
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• pp.24-32
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• 2009

The KNUC25 strain isolated from over-fermented whole Chinese cabbage kimchi was examined for its physiological characteristics using API 50 CHL system assay and identified as Lactobacillus paraplantarum by analysis of whole-cell protein SDS-PAGE pattern assay and similarity of 16S rDNA sequence. L. paraplantarum KNUC25 had a broad antimicrobial activity spectrum from Gram positive to Gram negative bacteria. Scanning electron micrograph analysis showed that KNUC25 might attack to cell surface of indicator cells and destruction can lead to inhibition of the cell growth. The antimicrobial substance of the KNUC25 strain was stable to various degrading enzymes and at high temperature and not a plasmid-born matter. Resistance to proteolytic enzymes showed that an antimicrobial activity of KNUC25 might not be caused by proteinous substance. Maximum production of antimicrobial substance was the exponential growth phase at $30^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.37 no.4
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• pp.350-354
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• 2009

A Gram-negative, alginate lyase-producing bacterium was isolated from the Haeundae Coast, Korea. The isolated strain N7151-6 produced alginate lyase. The optimal temperature and pH for growth were found to be $30^{\circ}C$ and pH 8.0, respectively. This strain can be grown at the NaCl concentration of 0-7% (w/v). Analysis of 16S rDNA sequence and physiological profiling indicated that the strain N7151-6 belonged to Pseudomonas sp. The enzyme alginate lyase produced by Pseudomonas sp. N7151-6 was partially purified by ultrafiltration (MWCO= 30 kDa). The optimum pH and temperature for the activity of the purified enzyme were found to be 7.0 and $30^{\circ}C$, respectively. The enzyme was stable at the pH range of 5.0-9.0 and temperature range of $23-30^{\circ}C$. The total activity of alginate lyase produced was reached about 110 unit/L.

• Microbiology and Biotechnology Letters
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• v.36 no.1
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• pp.82-85
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• 2008

Hyungbangjihwang-Tang (HT), an Oriental herbal formula, has been known to play a role which helps to recover vigor of human in the Orient. In this study, antibacterial substance (HTI) was purified from the ethyl-acetate extracts of HT by using $SiO_2$ column chromatography and HPLC, and the antibacterial effects of HTI were investigated. By using the CLSI broth micro-dilution assay, the activity of HTI was evaluated against human pathogenic Gram-positive and Gram-negative bacterial strains including the clinical isolates of methicillin-resistant Staphylococcus aureus. The results demonstrated that HTI showed broad spectrum antibacterial activities against all bacterial strains tested. In conclusion, HTI is an interesting new molecule for its potential in anti-infective drug discovery and for future studies on activity-structure relationship through analysis of its chemical structure.

• Microbiology and Biotechnology Letters
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• v.30 no.2
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• pp.151-156
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• 2002

This study was performed to obtain the thermostable $\beta$-glycosidase producing bacteria from hot spring of volcanic area at Atagawa in Japan. KNOUC 202 was selected because it showed thermostable $\beta$-glycosidase activity in sodium phosphate buffer(pH 6.8) at $70^{\circ}C$ for 4h, and it was identified. The strain was aerobic, asporogenic bacilli, immobile, gram negative, catalase positive, oxidase positive, and pigment-producing. Optimum growth was at $70~72^{\circ}C$, pH 7.0~7.2, and it could grow in the presence of 3% NaCl. The main fatty acids in cell were iso-15:0 and iso-l7:0. 16S rRNA sequence of KNOUC 202 showed 99.9% similarity with that of Thermus thermophilus ATCC 27634(HB8). Based on morphological, physiological, biochemical characteristics, cellular fatty acids profile and 16S rRNA sequence analysis, KNOUC 202 was identified as Thermus thermophilus.

• Microbiology and Biotechnology Letters
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• v.31 no.2
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• pp.129-134
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• 2003

The purpose of the present study was to screen the effective of lactic acid bacteria (LAB) as probiotics, which are able to protect aquacultural fish pathogenic bacteria, and investigate their characterization. Twenty strains of lactic acid bacteria were isolated from fish intestine, fermented fish foods and kimchis. These bacteria were screened for antagonistic activity against fish pathogenic bacteria. Seven tested LAB strains were able to inhibit the fish pathogenic bacteria, including Vibrio anguillarum, Edwardsiella tarda, and Streptococcus sp.. Of the probiotic candidates, BK19 strain isolated from fermented pollack viscera indicated the largest inhibition activity. Moreover, this strain showed a resistance over low pH and antibiotic agents. Therefore this probiotic candidate BK19 was finally selected and identified as a probiotic strain. This particular probiotic bacteria was identified as Lactobacillus sakei BK19 by biochemical characteristics and 165 rRNA PCR amplification.

• Microbiology and Biotechnology Letters
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• v.35 no.4
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• pp.292-297
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• 2007

The unicellular green alga, Haematococcus pluvialis used as a biological production system for astaxanthin. It accumulates large amounts of the red ketocarotenoid astaxanthin when exposed to various environmental stress such as active oxygen species and high light intensities. To induce astaxanthin biosynthesis of H. pluvialis, cells were incubated in either nitrate free at $25^{\circ}C$ under continuous high light intensity ($1,000\;{\mu}mol$ photons $m^{-2}s^{-1}$) for 2 days or high light stress only. Expressions of astaxanthin biosynthetic genes such as carotenoid hydroxylase, IPP isomerase and ${\beta}$-carotene ketolase were monitored under different culture conditions by using real time RT-PCR. All the subjected genes increased their expression under highlight and N-deprivation condition where a large amount of astaxanthin was accumulated.