• Journal of Microbiology and Biotechnology
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• 제11권5호
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• pp.763-771
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• 2001

Biphenyl dioxygenase (BPDO), which catalyzes the first step in the bacterial degradation of biphenyl and polychlorinated biphenyls, was characterized in Pseudomonas sp. B4. The bphA locus containing the four structural genes encoding BPDO were cloned and sequenced. A regulatory gene as well as a putative regulatory sequence were identified upstream of this locus. A transposase-like gene was found within a 1-kb region further upstream, thereby suggesting that the bphA locus may be carried on a transposable element. The three components of the BPDO enzyme have been separately overexpressed and purified from E. coli. The ferredoxin and terminal dioxygenase components showed biochemical properties comparable to those of two previously characterized BPDOs, whereas the ferredoxin reductase exhibited an unusually high lability. The substrate selectivity of BPDO was examined in vivo using resting cell assays performed with mixtures of selected polychlorinated biphenyls. The results indicated that para-substituted congeners were the preferred substrates. In vitro studies were carried out on a BPDO complex where the reductase from strain B4 we replaced by the more stable isoform from Comamonas testosteroni B-356. The BPDO enzyme had a specific activity of $0.26{\pm}0.02 {\mu}mol {min^-1}{mg^-1}\;of\;ISP_{BPH}$ with biphenyl as the substrate. The 2,3-, 4,4'-, and 2,4,4'-chlorobiphenyls were converted to single dihydrodiols, while 2,4'-dichlorobiphenyl gave rise to two dihydrodiols. The current data also indicated that 2,4,4'-trichlorobiphenyl was a better substrate than the 4,4'-dichlorinated congener.

• Journal of Microbiology and Biotechnology
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• 제32권10호
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• pp.1325-1334
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• 2022

Global warming has accelerated in recent decades due to the continuous consumption of petroleum-based fuels. Cyanobacteria-derived biofuels are a promising carbon-neutral alternative to fossil fuels that may help achieve a cleaner environment. Here, we propose an effective strategy based on the large-scale cultivation of a newly isolated cyanobacterial strain to produce phycobiliprotein and biodiesel, thus demonstrating the potential commercial applicability of the isolated microalgal strain. A native cyanobacterium was isolated from Goryeong, Korea, and identified as Pseudanabaena mucicola GO0704 through 16s RNA analysis. The potential exploitation of P. mucicola GO0704 was explored by analyzing several parameters for mixotrophic culture, and optimal growth was achieved through the addition of sodium acetate (1 g/l) to the BG-11 medium. Next, the cultures were scaled up to a stirred-tank bioreactor in mixotrophic conditions to maximize the productivity of biomass and metabolites. The biomass, phycobiliprotein, and fatty acids concentrations in sodium acetate-treated cells were enhanced, and the highest biodiesel productivity (8.1 mg/l/d) was achieved at 96 h. Finally, the properties of the fuel derived from P. mucicola GO0704 were estimated with converted biodiesels according to the composition of fatty acids. Most of the characteristics of the final product, except for the cloud point, were compliant with international biodiesel standards [ASTM 6761 (US) and EN 14214 (Europe)].

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 2005년도 2005 Annual Meeting & International Symposium
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• pp.154-164
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• 2005

Saccharomyces cerevisiae KNU5377 is a thermotolerant strain, which can ferment ethanol from wasted papers and starch at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. This strain showed alcohol fermentation ability to convert wasted papers 200 g (w/v) to ethanol 8.4% (v/v) at 40$^{\circ}C$, meaning that 8.4% ethanol is acceptable enough to ferment in the industrial economy. As well, all kinds of starch that are using in the industry were converted into ethanol at 40$^{\circ}C$ with the almost same rate as at 30$^{\circ}C$. Hyperthermic cell killing kinetics and differential scanning calorimetry (DSC) revealed that exponentially growing cells of this yeast strain KNU5377 were more thermotolerant than those of S. cerevisiae ATCC24858 used as a control. This intrinsic thermotolernace did not result from the stability of entire cellular components but possibly from that of a particular target. Heat shock induced similar results in whole cell DSC profiles of both strains and the accumulation of trehalose in the cells of both strains, but the trehalose contents in the strain KNU5377 were 2.6 fold higher than that in the control strain. On the contrary to the trehalose level, the neutral trehalase activity in the KNU5377 cells was not changed after the heat shock. This result made a conclusion that though the trehalose may stabilize cellular components, the surplus of trehalose in KNU5377 strain was not essential for stabilization of whole cellular components. A constitutively thermotolerant yeast, S. cerevisiae KNU5377, was compared with a relatively thermosensitive control, S. cerevisiae ATCC24858, by assaying the fluidity and proton ATPase on the plasma membrane. Anisotropic values (r) of both strains were slightly increased by elevating the incubation temperatures from 25$^{\circ}C$ to 37$^{\circ}C$ when they were aerobically cultured for 12 hours in the YPD media, implying the membrane fluidity was decreased. While the temperature was elevated up to 40$^{\circ}C$, the fluidity was not changed in the KNU5377 cell, but rather increased in the control. This result implies that the plasma membrane of the KNU5377 cell can be characterized into the more stabilized state than control. Besides, heat shock decreased the fluidity in the control strain, but not in the KNU5377 strain. This means also there's a stabilization of the plasma membrane in the KNU5377 cell. Furthermore, the proton ATPase assay indicated the KNU5377 cell kept a relatively more stabilized glucose metabolism at high temperature than the control cell. Therefore, the results were concluded that the stabilization of plasma membrane and growth at high temperature for the KNU5377 cell. Genome wide transcription analysis showed that the heat shock responses were very complex and combinatory in the KNU5377 cell. Induced by the heat shock, a number of genes were related with the ubiquitin mediated proteolysis, metallothionein (prevent ROS production from copper), hsp27 (88-fold induced remarkably, preventing the protein aggregation and denaturation), oxidative stress response (to remove the hydrogen peroxide), and etc.

• 한국미생물·생명공학회지
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• 제24권3호
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• pp.274-281
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• 1996

A bacterium producing Cyclodextrin Glucanotransferase (CGTase) and Cyclodextrinase (CDase) was isolated from soil, and named as Bacillus stearothermophilus KJ16. The growth of the isolated strain occurred in two steps, and syntheses of CGTase and CDase were dependedt on the growth cycle of the cell. CGTase was constitutively synthesized during the 1st growing phase, while CDase was synthesized inducibly during the 2nd growing phase. When the midium pH was controlled at 7.0 the maximum enzyme activities of CGTase and CDase were increased by 12-fold (1300 mU/ml) and 2-fold (225 mU/ml), respectively, compared with the pH-uncontrolled batch culture. The CGTase of the isolate converted soluble starch to CDs with the ratio of $\alpha$-CD:$\beta$-CD:$\gamma$-CD=42:46:12 at $55^{\circ}C$.The optimal pH and temperature of CGTase were 6.0 and $60^{\circ}C$, respectively and the optimal pH and temperature of CDase were 6.0 and $55^{\circ}C$. The molecular weights of the purified CGTase and CDase were estimated to be 65, 000 and 68, 000 dalton, respectively. Among several substrates, $\gamma$-CD was most rapidly hydrolyzed by the purified CDase.

• Applied Biological Chemistry
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• 제41권4호
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• pp.213-217
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• 1998

An assay for cytochrome P450 monooxygenase activity by determination of the products of organophosphate oxidation via inhibition of acetylcholinesterase was described. Extracts from strains of Oryzaephilus surinamensis selected for resistance to chlorpyrifos-methyl (QVOS 102), fenitrothion (VOS F) and malathion (VOS 3), and a standard susceptible strain VOS 48, were incubated with an organophosphate in the presence of a NADPH-generating system and acetylcholinesterase. The degree of inhibition of the acetylchoinesterase activity was converted to manooxygenase activity using standard curves for the inhibition of acetylcholiesterase by chlorpyrifos-methyl-oxon, fenitrooxon and malaoxan. Activity was detectable in VOS 48 and was present at different increased levels with the different organophosphates in the three resistant strains, suggesting that different forms of P450 might be involved in organophosphate oxidation in these insects. The assays were carried out using crude insect homogenates and much smaller samples of insect material than the standard aldrin to dieldrin assay. It should be possible to use the method for determination of monooxygenase activity in single insert.

• 미생물학회지
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• 제39권2호
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• pp.102-107
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• 2003

유류오염 토양으로부터 디젤에 대한 분해능이 있는 균주를 순수분리하였고, 이들 분리 균주의 액체 배양을통하여 균체 생육과 유화활성이 우수한 균주를 최종적으로 선별하였다. 생리,생화학적 특성 및 165 rDNA 염기서열 분석을 실시한 결과, Pseudomonas sp.로 분류 되었으며, Pseudomonas sp. GENECO 1으로 명명하였다. Bioscreen C를 이용하여 디젤 분해를 위한 배양 조건을 조사한 결과 최적 배양온도는 $30^{\circ}C$, 초기 pH는 7.0로 나타났다. Gas chromatography를 이용한 배양 시간별 잔류 디젤 성분분석 결과 96시간 이내에 1.0%의 디젤을 95%이상 분해하였다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.540-543
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• 2000

본연구에서는 Rhodococcus rhodochrous IGTS8 균주를 사용하여 고농도의 유상에서 탈황효율을 높이기 위한 오일 함유비, pH, 영양물질의 영향을 조사하였다. 오일 함유비에 의한 영향은 유상이 30%이하일 경우 그리 크지 않았으며, pH 조절에 의해 50%, 영양물질의 강화에 의해 32%의 탈황효율이 증가했다. 강화배지에서 pH를 조절하며 배양한 결과, 기존의 배양에 비해 136% 탈황효율이 증가했다.

• Geomechanics and Engineering
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• 제8권5호
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• pp.707-726
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• 2015

This paper investigates the time dependent behaviour of Haarajoki test embankment on soft structured clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. To analyse the PVD-improved subsoil, axisymmetric vertical drains were converted into equivalent plane strain conditions using three different approaches. The construction and consolidation of the embankment are analysed with the finite element method using a recently developed anisotropic model for time-dependent behaviour of soft clays. The constitutive model, namely ACM-S accounts for combined effects of plastic anisotropy, interparticle bonding and degradation of bonds and creep. For comparison, the problem is also analysed with isotropic Soft Soil Creep and Modified Cam Clay models. The results of the numerical analyses are compared with the field measurements. The results show that neglecting effects of anisotropy, destructuration and creep may lead to inaccurate predictions of soft clay response. Additionally, the numerical results show that the matching methods accurately predict the consolidation behaviour of the embankment on PVD improved soft clays and provide a useful tool for engineering practice.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1526-1533
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• 2006

The aim of this research was to confirm the existence of the thermal creep degradation by hydrides of Zr-2.5Nb pressure tube materials. Small punch creep tests were performed to obtain the relationship between a creep displacement and a loading period at $300^{\circ}C$. A creep stress and a creep strain rate were also converted from the previous results. The creep material constants and the creep stress exponents at the different hydride contents were compared. Finally the hydrides of the axial and circumferential section were observed using OM, SEM and TEM. The following conclusions were made: 1) The degradation of the thermal creep by hydrides was existed and it strongly depended on the hydride contents. 2) As the hydride contents were increased, the creep stress exponents (m) were also increased. 3) Even though the hydride was not precipitated in 50 ppm materials at $300^{\circ}C$, the degradation of thermal creep was found. Therefore, it was believed that this phenomenon strongly related to the hydride precipitation at room temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1585-1587
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• 2008

Fibroblast is constantly subjected to mechanical loads in connective tissues where mechanical signals are converted to intercellular biochemical events. The aim of this study is to understand the effects of tensile stress on the neurotrophin (NT) and transforming growth factor (TGF) expression of fibroblast in vitro. Nerve growth factor (NGF) stimulates fibroblast migration, and TGF is related to tissue repair. In this study, at the uniaxial stretch of 10% strain and frequency of 0.5 Hz, different resting times of 0, 20, and 60 min are placed in between 10 min stimulations periods. Results show increase in NGF mRNA levels and a substantial decrease in NT3 mRNA after 1 hr of stimulation, indicating that the tensile stress may regulate NGF and NT3, key factors for the neurocosmetic applications. The mRNA level for TGF-${\alpha}$ and TGF-${\beta}2$ had increased up to two-folds after 1 hr of stimulation, showing that the tensile stress may control TGF, an important part of wound healing.