• 한국미생물·생명공학회지
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• 제52권3호
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• pp.288-297
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• 2024

Fermented cooked rice is known to have remedial properties and good for health, but there is a lack of scientific knowledge to prove their beneficial effects. In this study, we investigated the presence of antibiotic-producing bacteria in fermented cooked rice. The probiotic properties of the bioactive isolates were also investigated. A total of seven pure isolates were isolated from fermented cooked rice prepared from parboiled cooked Aus rice in the lab following traditional methods. All the isolates were gram-positive, can grow at thermophilic range of temperatures, and all but CRS9 were able to coagulate milk. Three strains exhibited moderate to high broad-spectrum antibacterial activity against the test bacteria including Shigella brodie, Bacillus cereus, Escherichia coli, Pseudomonas sp., Staphylococcus aureus, and Proteus sp. Analysis of 16S rDNA sequences of the strain CRS8 and CRS11 showed that they belong to the genus Bacillus as they exhibited >99% identity to several strains of Bacillus. Both strains could survive the highly acidic conditions and can tolerate bile acid indicating their potential to be the candidate probiotic strains. The strain CRS8 was resistant to penicillins and cephalosporins including amoxicillin, penicillin, cephalothin, however, the CRS11 was sensitive to all the antibiotics tested. This is the first report that fermented cooked rice is a source of antibiotic-producing Bacillus sp. The probiotic properties of the Bacillus isolates from fermented cooked rice were also investigated for the first time.

• 한국지반공학회논문집
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• 제23권4호
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• pp.25-32
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• 2007

도로 성토재 및 구조물 뒤채움재로 점성토 활용의 필요성이 증가함에 따라 보강재로 배수성을 갖고 있는 토목섬유 부직포가 점차 주목을 받고 있으나, 현장 보강토구조물에서 부직포의 변형거동을 분석한 사례는 거의 없으며, 그 이유는 부직포의 경우 지오그리드나 직포에 비해 강성이 작고 변형률이 크며 스트레인 게이지를 이용한 계측이 곤란하기 때문이다. 본 연구에서는 스트레인 게이지를 이용하여 부직포의 변형거동을 보다 간편하게 계측할 수 있는 방법을 제안하였고, 이를 실내시험과 2개의 실물보강토옹벽에 적용하여 유용성 여부를 검토하였다. 구속압 70kPa 하에서 실시한 실내 광폭인장시험의 경우 스트레인 게이지에 의해 계측된 부직포의 국부변형은 LVDT에 의해 계측된 전체변형과 유사한 패턴으로 거동하는 것으로 나타났다. 실물보강토옹벽에서 부직포의 변형범위는 직포나 지오그리드보다 크게 나타나나, 이들 보강재와 변형 패턴이 유사하고, 16개월 동안 정상적으로 작동하는 것으로 나타났다. 따라서, 본 연구에서 제안한 스트레인 게이지에 의한 부직포의 변형계측방법은 매우 유용한 것으로 판단된다.

• 대한토목학회논문집
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• 제28권6C호
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• pp.349-358
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• 2008

본 연구에서는 고베 공항 해저 충적 점토를 대상으로 한 신뢰성 침하 해석을 위해 각종 입력 물성치의 불확실성을 확률 통계 이론에 근거하여 조사하였고, Terzaghi 압밀 방정식을 목적 함수로 AFOSM 법을 적용하여 파괴 확률을 정식화하였다. 신뢰성 해석 결과, 목표침하량을 평균침하량 ${\pm}10%,\;{\pm}25%$로 설정한 경우, 발생확률은 각각 30~50%, 60%~90%로 나타났다. 이는 대상 지반의 확률변수의 변동계수가 과거의 연구보고 범위 내에 있음을 고려할 때, 목적함수로 Terzaghi 압밀방정식을 이용한 경우 침하량의 허용 오차 범위는 평균침하량 ${\pm}10%$가 적절할 것으로 사료된다. 또한, 감도 분석 결과 해석에 크게 영향을 미치는 인자는 압축 계수, 모델, 압밀 항복 응력의 불명확성으로 나타났다. 이는 정밀도가 높은 사전 침하량의 예측을 위해서는 현장의 응력 변형 조건을 충실하게 반영한 시험을 수행하여 신뢰도가 높은 물성치를 구하는 것이 매우 중요한 것임을 설명한다.

• Earthquakes and Structures
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• 제10권2호
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• pp.329-350
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• 2016

A parametric study was conducted to investigate the seismic deformation demands in terms of drift ratio, plastic base rotation and compression strain on rectangular wall members in frame-wall systems. The wall index defined as ratio of total wall area to the floor plan area was kept as variable in frame-wall models and its relation with the seismic demand at the base of the wall was investigated. The wall indexes of analyzed models are in the range of 0.2-2%. 4, 8 and 12-story frame-wall models were created. The seismic behavior of frame-wall models were calculated using nonlinear time-history analysis and design spectrum matched ground motion set. Analyses results revealed that the increased wall index led to significant reduction in the top and inter-story displacement demands especially for 4-story models. The calculated average inter-story drift decreased from 1.5% to 0.5% for 4-story models. The average drift ratio in 8- and 12-story models has changed from approximately 1.5% to 0.75%. As the wall index increases, the dispersion in the calculated drifts due to ground motion variability decreased considerably. This is mainly due to increase in the lateral stiffness of models that leads their fundamental period of vibration to fall into zone of the response spectra that has smaller dispersion for scaled ground motion data set. When walls were assessed according to plastic rotation limits defined in ASCE/SEI 41, it was seen that the walls in frame-wall systems with low wall index in the range of 0.2-0.6% could seldom survive the design earthquake without major damage. Concrete compressive strains calculated in all frame-wall structures were much higher than the limit allowed for design, ${\varepsilon}_c$=0.0035, so confinement is required at the boundaries. For rectangular walls above the wall index value of 1.0% nearly all walls assure at least life safety (LS) performance criteria. It is proposed that in the design of dual systems where frames and walls are connected by link and transverse beams, the minimum value of wall index should be greater than 0.6%, in order to prevent excessive damage to wall members.

• 한국식품영양과학회지
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• 제36권12호
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• pp.1617-1621
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• 2007

전주지역에서 김장시기에 수거한 김치의 미생물 조성과 관능성적간의 상관성을 조사하여 다음의 결과를 얻었다. 김치는 21 표본 중 11 표본에서 L. mesenteroides가 $8.31{\sim}11.27log\;CFU/g$의 범위에서 지배균으로, 16 표본에서 L. sakei가 $7.97{\sim}10.57log\;CFU/g$의 범위에서 차지배균으로 나타났다. 김치의 관능성적은 총균수, 지배균수, 차지배균수, 균종수 등 계량적 특성에는 유의적 상관성이 없었다. 가장 맛이 좋은 김치 3종은 모두 지배균이 L. mesenteroides, 차지배균은 L. sakei인데 비해 가장 맛이 없는 김치 3종은 지배균에 L. sakei가 많아 김치의 맛은 주요 미생물의 균종의 조합과 관련이 있었다. 효모는 8표본에서 $3.80{\sim}4.6log\;CFU/g$의 범위로 검출되었으며 모두 Saccharomyces servazzii로 동정되었다. 곰팡이는 전혀 검출되지 않았다. 효모 균수와 김치의 관능성적은 유의적 상관성이 없었다.

• Journal of Welding and Joining
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• 제23권3호
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• pp.68-75
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• 2005

The fatigue life of welded joints is associated with crack initiation and propagation life. Theses cannot be easily separated, since the definition of crack initiation is vague due to the initiation of multiple cracks that are distributed randomly along the weld toes. In this paper a method involving a notch strain and fracture mechanical approach, which considers the characteristics of welded joints, e.g. welding residual stress and statistical characteristics of multiple cracks, is proposed, in an attempt to reasonably estimate these fatigue lives. The fatigue crack initiation life was evaluated statistically, e.g. the probability of failure occurrence in 2.3, 50 and $97.7\%$, in which the cyclic response of the local stress/strain hi the vicinity of the weld toes and notch factors derived by the irregular shape of the weld bead are taken into account. The fatigue crack propagation life was simulated by using Monte-Carlo method in consideration of the Ad-factor and the mechanical behavior of mutual interaction/coalescence between two adjacent cracks. The estimated total fatigue life, $(N_T)_{P50\%}$, as a sum of crack initiation and propagation life under the probability of failure occurrence in $50\%$ showed a good agreement with the experimental results. The developed technique for fatigue lift estimation enables to provide a quantitative proportion of crack initiation and propagation life in the total fatigue life due to the nominal stress range, ${\Delta}S$.

• Journal of Microbiology and Biotechnology
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• 제23권6호
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• pp.872-877
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• 2013

In a previous study, we isolated and reported a second species of the Saccharophagus genus, Saccharophagus sp. strain Myt-1. In the present study, an alginate lyase gene (algMytC) from the genomic DNA of Myt-1 was cloned and characterized. The DNA sequence fragment obtained contained an open reading frame of 1,032 bp that encoded a protein of 343 amino acids with an estimated molecular mass of 37.6 kDa and a pI of 6.60. The deduced protein, AlgMytC, had the conserved amino acid sequences (RTELREM, QIH, YFKAGVYNQ) of the polysaccharide lyase family 7. A BLAST homology search indicated that AlgMytC shared an amino acid sequence identity of 95.9% with alg7A of S. degradans 2-40. The cloned and purified AlgMytC protein showed optimal activity at $40^{\circ}C$, and retained more than 90% of its total activity even after treatment at $25^{\circ}C$ for 24 h. AlgMytC was very alkaliphilic with an optimal pH of 9.0, and more than 90% of its activity was retained in the pH range 8.5-10.0. Moreover, AlgMytC was stable over a wide pH range. The activity of AlgMytC was also stable in the presence of various detergents.

• Applied Biological Chemistry
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• 제13권3호
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• pp.237-242
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• 1970

밀감류 등의 고미 성분의 일종인 Naringin을 분해하는 효소를 생성하는 사상균을 분리 선별하여 실용화에 알맞는 S-1 균주 효소 Naringinase의 몇가지 효소학적 성질을 검토한 결과는 다음과 같다. 1. Naringinase S-1은 Pectinase의 생성이 비교적 약하였으며 최적 활성 pH의 범위는 pH $3.0{\sim}5.0$사이었다. 2. Naringinase의 생성은 배지에 Naringin첨가에 의하여 많이 증가되었다. 3. 적당한 효소농도 이상에서는 Naringin의 분해는 0.1% 기질 농도에서는 80% 까지는 거의 직선적이었으며 고농도의 기질농도에서는 활성도가 낮았다. 4. 최적 활성 pH는 $50^{\circ}C$이었으며 열안정성은 $50^{\circ}C$에서 2시간 열처리에 의하여서는 별 역가의 감소가 없었으나 60.C에서 30분에 40% $70^{\circ}C$에서 10분만에 70%의 불활성화를 나타내었다. 5. Glucose는 효소작용에 있어 경쟁적으로 저해하였으며 저해정수는 1.5 Mol이었고 Sucrose에 의한 저해는 l Mol 농도에서 56%의 저해를 가져왔다.

• Mycobiology
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• 제30권3호
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• pp.160-165
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• 2002

Aspergillus niger has been used as a host to express many heterologous proteins. It has been known that the presence of an- abundant protease is a limiting factor to express a heterologous protein. The protease deficient mutant of A. niger was obtained using UV-irradiation. A total of $1{\times}10^5$ spores were irradiated with $10{\sim}20%$ survival dose of UV, 600 $J/m^2$ at 280 nm, and the resulting spores were screened on the casein-gelatin plates. Ten putative protease deficient mutants showing the reduced halo area around colonies were further analyzed to differentiate the protease deficient mutant from other mutant types. Among ten putative mutants, seven mutants showed significant growth defect on nutrient rich medium and two mutants appeared to be the secretory mutants, which resulted in the impaired secretion of extracellular proteins including proteases. A mutant $pro^--20$ showed reduced halo zone without any notable changes in growth rate. In addition, the starchdegrading and glucose oxidase activities in the culture filtrate of $pro^--20$ mutant showed the similar range as that of the parental strain, which suggested that the $pro^--20$ mutant ought to be the protease deficient mutant rather than a secretory mutant. The reduced proteolytic activity of the $pro^--20$ was demonstrated using SDS-fibrin zymography gel. The reduced extracellular proteolysis was quantified by casein degradation assay and, comparing with the parental strain, less than 30% residual extracellular protease activity was detected in the culture filtrate of the $pro^--20$ mutant. The bio-activity of an exogenously supplemented hGM-CSF(human Granulocyte-Macrophage Colony Stimulating Factor) in the culture filtrate of $pro^--20$ mutant was detected until eight times more diluted preparations than that of the parental strain.

• Journal of Microbiology and Biotechnology
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• 제23권1호
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• pp.56-63
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• 2013

We have characterized the putative ${\alpha}$-glucosidase gene (st2525) selected by total genome analysis from the acidothermophilic crenarchaeon Sulfolobus tokodaii strain 7. The ORF was cloned and expressed as a fusion protein in Escherichia coli, and recombinant ST2525 was purified by Ni-NTA affinity chromatography. Maximum activity was observed at $95^{\circ}C$ and pH 4.0, and the enzyme exhibited stability with half-lives of 40.1 min and 7.75 min at extremely high temperatures of $100^{\circ}C$ and $105^{\circ}C$, respectively. The enzyme retained at least 85% of its maximal activity in the pH range of 4.0-11.0. ST2525 exclusively hydrolyzed ${\alpha}$-1,4-glycosidic linkages of oligosaccharides in an exo-type manner, with highest catalytic efficiency toward maltotriose. The enzyme also displayed transglycosylation activity, converting maltose to isomaltose, panose, maltotriose, isomaltotriose, etc. From these results, ST2525 could be potentially useful for starch hydrolysis as well as novel synthesis of oligosaccharides in industry.