• 한국미생물·생명공학회지
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• 제22권5호
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• pp.522-530
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• 1994

Bacteriocin-producing lactic acid bacteria, Lactococcus sp. HY 449, was isolated from dairy products. Using response surface methodology, the various concentrations of medium compo- nents (tryptone, glucose, yeast extract, tween 80, and initial pH) were tested to find the optimum conditions for maximum bacteriocin production and growth of Lactococcus sp. HY 449. Central composite design was used to control the concentrations of medium components in the experiment. Bacteriocin production and cell growth of Lactococcus sp. HY 449 were most affected by glucose and yeast extract. Estimated optimum growth conditions of Lactococcus sp. HY 449 were as follows; tryptone 1.08%, glucose 1.129%, yeast extract 0.674%, tween 80 0.11%, and initial pH 7.19. Also estimated optimum conditions for bacteriocin production were tryptone 0.937%, glucose 1.108%, yeast extract 0.163%, tween 80 0.09%, and initial pH 6.98.

• Journal of Microbiology and Biotechnology
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• 제26권11호
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• pp.1829-1835
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• 2016

Dental caries is caused by cariogenic biofilm, an oral biofilm including Streptococcus mutans. Recently, the prevention of dental caries using various probiotics has been attempted. Lactococcus lactis HY 449 is a probiotic bacterium. The aim of this study was to investigate the effect of L. lactis HY 449 on cariogenic biofilm and to analyze its inhibitory mechanisms. Cariogenic biofilm was formed in the presence or absence of L. lactis HY 449 and L. lactis ATCC 19435, and analyzed with a confocal laser microscope. The formation of cariogenic biofilm was reduced in cultures spiked with both L. lactis strains, and L. lactis HY 449 exhibited more inhibitory effects than L. lactis ATCC 19435. In order to analyze and to compare the inhibitory mechanisms, the antibacterial activity of the spent culture medium from both L. lactis strains against S. mutans was investigated, and the expression of glucosyltransferases (gtfs) of S. mutans was then analyzed by real-time RT-PCR. In addition, the sucrose fermentation ability of both L. lactis strains was examined. Both L. lactis strains showed antibacterial activity and inhibited the expression of gtfs, a nd t he d ifference b etween both strains did not show. In the case of sucrose-fermenting ability, L. lactis HY 449 fermented sucrose but L. lactis ATCC 19435 did not. L. lactis HY 449 inhibited the uptake of sucrose and the gtfs expression of S. mutans, whereby the development of cariogenic biofilm may be inhibited. In conclusion, L. lactis HY 449 may be a useful probiotic for the prevention of dental caries.

• 한국미생물·생명공학회지
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• 제29권3호
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• pp.155-161
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• 2001

Lactrococcus sp. HY449균줄르 M17-glucose broth에 배양하여 배양 상등액으로부터 propanol-actone 침전 ion-exchange chromatography gel-filtration chromatography 및 reverse-phase chroamtography 등을 통하여 비활성 25,600,000 BU/mg 인 순수한 bacteriocin 을 정제하였다. 정제 과정 주에서 ion-exchange chromatography 단계에 서는 35.3%의회수율이 7.3%로 감소하였다. Reverse-Phase chromatography에선 3.3%의 회수율을 보였고 활성도는 413.5배로 증가하였다. Tricine-SDS 전기영도 결과 bacteriocin 은 단일 밴드로 나타났으며, N-말단 아미노산 서열 분석을 수행한 결과 $NH_2$-IIe-Leu-Pro-GIn로 확인되었다. 아미노산조정 분석결과를 바탕으로 분자량을 예측한 결과 본 bacteriocin은 32개의 아미노산으로 이루어져 있으며 분자량은 3.6kDa인 것으로 추정되었다.

• 한국미생물·생명공학회지
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• 제22권3호
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• pp.266-270
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• 1994

A bacteriocin was isolated from the supernatant fluid of M17G broth culture of Lactococcus sp. HY 449 strain, which showed strong inhibitory activity against the growth of selective indicator strain, Lactobacillus fermentum IFO3023. When the bacteriocin wasa added to the growing indicator cells or cell suspensions, viable cells and optical density were density were decreased, indicating bacteriolytic mode of action. Electron microscopic observation of indicator cells treated with bacteriocin revealed apparent damages on the cell surface and eventual lysis of cell walls.

• 한국미생물·생명공학회지
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• 제22권3호
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• pp.259-265
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• 1994

A bacteriocin-producing lactic acid bacteria was isolated from contaminated milk products, which was identified by using the API50 CH kit as Lactococcus lactis subsp. lactis with reliability of 98%. Fatty and analysia of the cell membrane showed that this strain contained same fatty acids profiles as type strain, Lactococcus lactis subsp. lactis ATCC 19435. The bacteriocin of Lactococcus sp. HY 449 showed relatively wide range of inhibition spectrum against gram positive and some gram negative bacteria such as Escherichia coli and maintained the inhibitory activity between pH2.0 and pH9.0 The thermostability of this bacteriocin was higher in acidic solution than in distilled water and was stable at 60$\circ $C for 1 hour.

• Journal of Dairy Science and Biotechnology
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• 제12권2호
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• pp.1-10
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• 1995

• Computers and Concrete
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• 제20권4호
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• pp.449-459
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• 2017

Fresh and hardened behaviors of a new hybrid fiber (steel fiber, polyvinyl alcohol fiber and calcium carbonate whisker) reinforced cementitious composites (HyFRCC) with admixtures (fly ash, silica fume and water reducer) have been studied. Within the limitations of the equipment and testing program, it is illustrated that the rheological properties of the new HyFRCC conform to the modified Bingham model. The relations between flow spread and yield stress as well as flow rate and plastic viscosity both conform well with negative exponent correlation, justifying that slump flow and flow rate test can be applied to replace the other two as simple rheology measurement and control method in jobsite. In addition, for the new HyFRCC with fly ash and water reducer, the mathematical model between the rheological and mechanical properties conform well with the quadratic function, and these quadratic function curves are always concave upward. Based on mathematical analysis, an optimal range of rheology/ flowability can be identified to achieve ideal mechanical properties. In addition, this optimization method can be extended to PVA fiber reinforced cement-based composites.

• 대한화장품학회지
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• 제28권1호
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• pp.150-165
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• 2002

The purpose of this study was to evaluate bacteriocin activity against human flora. Lactobiocin, a bacteriocin produced by Lactococcus sp. HY 449, inhibited the growth of Starphylococcus epidermidis, Starphylococcus aureus, Streptoccoccus pyogenes and Propionibacterium acnes. When crude bacteriocin was added to indicator cells during logarithmic growth, the optical density(O.D 650nm) of cells without bacteriocin increase after 5h of incubation. Whereas in the presence of bacteriocin, the O.D of cell suspensions decreased. The similar patterns were observed for absorbance readings at 280 nm and 260 nm. The release of cellular components when cell were treated with Lactobiocin suggests some degree of membrane damage or cell lysis. Scanning electron microscopy of cells following treatments with Lactobiocin in PBS buffer revealed disruptures of cell morphology. These results indicate that bacteriocin appears to cause cell lysis of tested strains. In cytotoxicity on human fibroblast, LD$\_$50/ of Lactobiocin was ca. 50 mg/ml and no change was observed cell proliferation at the same concentration. Any irritation and allergic reaction did not observed when evaluated by human patch test for Lactobiocin.

• 미생물학회지
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• 제30권6호
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• pp.444-449
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• 1992

낙동강 하구생태계에 분포한 종속영양세균의 환경 변화에 따른 군집구조의 변화를 파악하기 위해 총 858 균주를 분리하여 수리학적 방법에 의해 분석하였다. 종의 다양성(H') 은 1.54-3.49 로, 하구언 건설 전의 수치와 큰 차이가 없었으나, 균등성지수(evenness index)(J') 는 0.31-0.80 으로 감소하였다. Physiological tolerance index 중 수온에 대한 지수(P') 는 수심이 얕은 정점에서, pH 와 염분에 대한 $P_{h}$ 및 $P_{s}$ 는 담수와 해수가 교차하는 정점에서 높았다. 우점의 cluster 를 속 (genus) 수준에서 동정한 결과 Aeromonas, Vibrio, Pseudomonas, Acinetobacter-Morexella, Alcaligenes, Flavobacterium, Micrococcaceae, Enterobacteriaceae 등으로 분류되어 하구언 축조 전과 동일한 종류의 세균뷴포를 나타냈으나 그 출현비율은 달랐다. 이와 같은 결과로 미루어 하구언 축조 등에 따른 낙동강 하구역의 환경변화는 분포세균의 종류보다는 생리적 특셩에 영양을 미쳐 특정종의 우점을 나타나게 한 것으로 사료된다.

• 한국축산식품학회지
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• 제30권3호
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• pp.449-457
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• 2010

본 시험에서는 산란계에 대한 인진쑥, 녹차, 오미자, 겨우살이의 혼합 비율을 달리한 3종 추출물의 사료 내 첨가 급여가 난 생산성, 계란 품질, 혈액 특성 및 계란 저장성에 미치는 영향을 조사하기 위하여 35주령 산란계(Hy-Line Brown) 160수를 공시하여 4처리 4반복, 반복 당 10수씩 배치하고 10주간 사양시험을 실시하였다. 시험처리는 대조구(C)와 시험 사료에 혼합 비율을 달리한 3종의 추출물을 200 ppm 수준으로 첨가한 약용식물 추출물 처리구(T1, T2, T3)를 두었다. 산란율, 일 산란량 및 사료 요구율은 대조구에 비해 모든 처리구에서 유의하게 개선되었다(p<0.05). Haugh unit 및 난황색은 처리구 간 차이는 있었으나 전반적으로 대조구에 비해 유의하게 증가하였다(p<0.05). 난각질에서는 유의한 차이가 관찰되지 않았다. 혈액 내 총 콜레스테롤 함량은 대조구에 비해 모든 처리구에서 유의하게 감소하였으며(p<0.05), 중성 지방은 유의성은 나타나지 않았으나 감소하는 경향을 보였다. 간 및 신장 기능의 이상 여부를 나타내는 혈액 생화학 지표 역시 유의하게 감소하거나 감소하는 경향을 보였다(p<0.05). 혈액 총 항산화 활성은 대조구에 비해 다소 증가하는 경향을 보였으나 유의성은 인정되지 않았다. 저장 기간에 따른 Haugh unit 및 지방과 산화물가의 변화를 조사한 결과, 계란 보관 14일, 21일째에 Haugh unit이 대조구에 비해 유의하게 높았으며(p<0.05), 3일 및 7일째 역시 통계적 유의성은 인정되지는 않았으나 추출물 처리시 저장 기간에 따른 Haugh unit의 저하를 감소시키는 경향을 관찰하였다. 지방과산화물가 역시 처리 구간 차이는 있었으나 대조구에 비해 유의하게 감소하는 것을 확인할 수 있었다(p<0.05). 본 연구 결과, 인진쑥, 녹차, 오미자, 겨우살이의 혼합 비율을 달리한 약용식물 추출물의 산란계 사료 내 첨가급여는 계란 생산성을 향상시키고, 건강 유지에 긍정적인 영향을 미쳤으며, 난황색 및 Haugh unit 등의 계란 내부품질을 개선시켰을 뿐만 아니라, 저장 기간에 따른 계란의 품질 저하를 감소시켜 사료 첨가제로서의 이용 가능성을 제시하였다.