• 한국미생물·생명공학회지
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• 제24권6호
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• pp.733-737
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• 1996

The formation of microbial films(biofilm) by a non-sulfur phototrophic bacteria, Rhodopseudomonas capsulata, on inorganic media was studied. Porous ceramic beads(PCB) were superior to other immobilizing media for the biofilm formation in a packed-bed reactor. It was found that the formation of microbial films favored a lower hydraulic retention time, showing a higher ratio of cells attatched to the media to those suspended in the solution. The cell concentration in the biofilm reactor was as high as 11,400mg/l, which is 8-folds of the cell concentration in an ordinary suspended treatment. It was observed that the formation of micribial film by R. capsulata followed a general serial process of cell attachment, microcolony formation, and biofilm formation. The microbial films thus formed was very stable even for an extremely high volumetric BOD loading rate of 15gBOD/l day. The scanning electron micrographs of the microbial films showed that the cells were attached to both the surface and pores of the media.

• 생명과학회지
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• 제21권10호
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• pp.1473-1480
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• 2011

퍼클로레이트($ClO_4^-$)는 지표수 및 토양/지하수에서 검출되는 오염물이다. 미생물은 퍼클로레이트를 무해한 최종산물로 환원시킬 수 있으므로 퍼클로레이트제거는 미생물을 이용한 방법이 가장 적절한 것으로 알려졌다. 미생물이 퍼클로레이트를 환원시키기 위해서는 전자 공여체가 필요하다. 퍼클로레이트를 환원하기 위한 기존의 기술들은 전자 공여체로서 유기물을 사용하는 종속영양방식의 퍼클로레이트환원세균을 사용한다. 그래서 종속영양 방식으로 퍼클로레이트를 연속 제거하기 위해서는 지속적으로 유기물을 공급해야 하므로 처리비용이 많이 든다. 본 연구에서는 원소 황 입자와 활성 슬러지를 이용하여 독립영양방식의 퍼클로레이트제거가능성을 조사하였다. 입자상 황은 비교적 값이 저렴하고 활성 슬러지는 하수처리장으로부터 쉽게 구할 수 있는 장점이 있다. 회분배양 실험결과 활성 슬러지 미생물은 전자 공여체로서 황 입자가 존재할 때 퍼클로레이트를 제거할 수 있다는 것이 증명되었다. 이러한 퍼클로레이트 분해는 퍼클로레이트가 분해됨에 따라 생성되는 Cl-의 몰 농도를 통해 검증할 수 있었다. 독립영양방식의 $ClO_4^-$ 제거공정에 사용된 황 입자의 표면에 간균 형태의 미생물들이 존재한다는 것을 주사전자현미경을 통해 관찰하였다. 그래서 황 입자가 생물막을 형성하기 위한 담체로도 작용할 수 있다는 것을 알 수 있었다. 황입자가 첨가된 $ClO_4^-$ 분해성 농화 배양으로부터 채취한 생물막의 미생물군집조성은 접종균으로 사용된 활성 슬러지의 그것과는 다름이 DGGE 분석결과 나타났다.

• 한국치위생학회지
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• 제5권2호
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• pp.131-145
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• 2005

There are normal inhabitants doing medically useful functions in the body. There are many kinds of bacteria performing specific functions in the oral cavity. Two strains of lactic add bacteria were isolated from normal inhabitants of children's oral cavity, which inhibited the production of volatile sulfur compounds by anaerobic bacteria. The authors identified the isolates by 16S rDNA partial sequencing. 1. Two isolates were Gram-positive bacilli and produced hydrogen peroxide. 2. When Streptococcus mutans was cultured in the media, the mean weight of formed artificial plaque on the orthodontic wires was $124.4{\pm}30.4$ mg, whereas being reduced to $5.2{\pm}2.0$ mg and $10.6{\pm}6.6$ mg in the media cultured with Streptococcus mutans and each isolate, respectively(p<0.05). 3. The number of viable cells of Streptococcus mutans was $3.4{\times}10^9$ per ml in the cultured solution, whereas those of Streptococcus mutans in the combined culture with each of isolates were $4.6{\times}10^8$ and $2.4{\times}10^8$ per ml. 4. The optical density was 1.286 in the supernatant of Fusoacterium nucleatum after vortexing for 30 minutes, whereas in the supernatant of combined Fusoacterium nucleatum and each isolate, they were reduced to 0.628 and 00497, which the percentages of coaggregation between them were 2904% and 57.8%, respectively. 5. The optical density of Fusoacterium nucleatum precipitate was 1.794 in the culture media containing cysteine and $FeSO_4$ being reduced to 1.144 and 0.915 in the coaggregated precipitates of Fusoacterium nucleatum and each isolate. 6. The similarity values of 16S rDNA sequence between each of isolates and Lactobacillus salivarius subsp. salicinius were 99.60% and 99.73%, respectively, meaning that isolates were Lactobacillus salivarius subsp. salicinius. These results indicated that two strains isolated from children's saliva, which inhibited the formation of plaque and the production of volatile sulfur compounds, were identified as Lactobacillus salivarius subsp. salicinius.

• Environmental Analysis Health and Toxicology
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• 제14권3호
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• pp.121-126
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• 1999

The present paper describes a study of the photochemical kinetics and its oxidation mechanism of DBT. The photolysis of DBT in aqueous solution media have shown to have significant oxidation activities for the photolytic desulfurization of DBT. The oxidation effect was more pronounced in 4 % NaCl solution. A mechanism was proposed that the desulfurization process arise from the substution of sulfur by the hydroxyl radicals in different aqueous medium.

• 한국수소및신에너지학회논문집
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• 제21권1호
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• pp.12-18
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• 2010

Photobiological hydrogen production using Rhodobacter sphaeroides KD131 was studied on the effect of light intensities and nitrogen sources. Media containing malate and glutamate were shown higher hydrogen production rate than that containing succinate and $(NH_4)_2SO_4$ at the $110\;W/m^2$ illumination by halogen lamp at $30^{\circ}C$. Media lacking glutamate as the nitrogen source exhibited higher hydrogen production than that containing glutamate. Initial cell concentration was optimized to 1.0 at the absorbance of 660 nm. Hydrogen production was increased by increasing the light intensity from 0 to $216\;W/m^2$ but the increasing rate declined over $108\;W/m^2$.

• 환경생물
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• 제29권4호
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• pp.265-273
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• 2011

Bacterial diversity based on the denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA gene sequences was determined for soil samples from two abandoned mine sites and the corresponding enrichment cultures using soil sample as key inoculum. Sequencing analysis of DGGE bands obtained from both the soil samples matched mostly with sequences of uncultured and newly described organisms, or organisms recently associated with the acid mine drainage environment. However, the enrichment of soil samples in ferrous sulfate and elemental sulfur media yielded sequences that were consistent with well-known iron- and sulfur-oxidizing acidophilic bacteria. Analysis of enrichment cultures of soil samples from Dalsung mine revealed abundant ${\gamma}$-$Proteobacteria$, whereas that of Gubong mine sample displayed acidophilic groups of ${\gamma}$-$Proteobacteria$, ${\alpha}$-$Proteobacteria$, $Actinobacteria$ and $Firmicutes$. Chemical elemental analysis of the mine samples indicated that the Dalsung site contained more iron and sulfate along with other toxic components as compared with those of the Gubong site. Biogeochemistry was believed to be the primary control on the acidophilic bacterial group in the enrichment samples.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1523-1530
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• 2007

The first reduction peak of the cyclic voltammogram (CV) for sulfur reduction in dimethyl sulfoxide has been studied using time resolved Fourier transform electrochemical impedance spectroscopic (FTEIS) analysis of small potential step chronoamperometric currents. The FTEIS analysis results reveal that the impedance signals obtained during short potential steps can be resolved into electron transfer reactions of two different time constants in a high frequency region. The FTEIS method provides snap shots of impedance profiles during an earlier phase of the reaction, leading to time resolved EIS measurements. Our results obtained by the FTEIS analysis are consistent with a series of electron transfer and chemical equilibrium steps of a complex reaction, making up an ECE (electrochemical-chemical-electrochemical) mechanism postulated from the results of computer simulation.

• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.27-30
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• 2011

A sub-cooled liquid nitrogen cooling system is known as a most promising method to develop large scale superconducting apparatuses such as superconducting fault current limiters and superconducting cables [1]. Gaseous helium (GHe), gaseous nitrogen ($GN_2$) and sulfur hexafluoride ($SF_6$) are commonly used for designing an high voltage applied superconducting device as an injection gaseous medium [2, 3]. In this paper, the analysis on the dielectric characteristics of GHe, $GN_2$ and $SF_6$ are conducted by designing and manufacturing sphere-to-plane electrode systems. The AC withstand voltage experiments on the various gaseous insulation media are carried out and the results are analyzed by using finite element method (FEM) considering field utilization factors (${\xi}$). It is found that the electric field intensity at sparkover ($E_{MAX}$) of insulation media exponentially decreases according to ${\xi}$ increases. Also, the empirical expressions of the functional relations between $E_{MAX}$ and ${\xi}$ of insulation media are deduced by dielectric experiments and computational analyses. It is expected that the electrical insulation design of applied superconducting devices could be performed by using the deduced empirical formulae without dielectric experiments.

• 한국응용곤충학회지
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• 제51권4호
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• pp.357-364
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• 2012

토마토 재배에 사용되는 농자재를 이용하여 곤충 병원성 곰팡이인 Beauveria bassiana의 병원성에 끼치는 영향을 조사하였다. Chlorothalonil 등 13종의 살균제 첨가 배지에서는 B. bassiana 균사가 전혀 생장하지 못하였고 chlorothalonil 등 12종의 살균제 첨가 배지에서 균총이 형성되지 않았다. 살충제와 친환경자재를 첨가한 모든 배지에서 균사가 생장하고 포자가 형성되었지만 대부분 배지에서 무처리와 비교했을 때 유의차를 보였다. 온실가루이에 대한 살충력은 B. bassiana 단독처리일 때보다 화학살균제(polyoxin B, mandipropamid)와 친환경농자재(sulfur) 혼합시 떨어졌으며 화학살충제(pyridaben, dinotefuran)와 식물추출물 유래 친환경농자재(pyrethrum) 혼합시에는 유의차가 없었으며 온실에서 살균제인 polyoxin B의 혼합으로 온실가루이에 대한 B. bassiana의 감염력이 떨어지는 것을 확인하였다.

• 생물환경조절학회지
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• 제27권2호
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• pp.140-146
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• 2018

코이어 더스트와 수피를 동일한 비율로 혼합한 상토로 '싼타' 딸기를 수경재배할 때 기비로 혼합된 유황의 처리수준 차이가 토양용액의 중탄산 농도, pH, 식물체의 생육 및 무기원소 흡수량에 미치는 영향을 구명하기 위해 본 연구를 수행하였다. 혼합상토 조제시 유황분말을 0, 0.23, 0.45, 0.90 및 $1.80g{\cdot}L^{-1}$으로 조절하여 혼합하였고, 작물 재배 중에는 중탄산 농도를 $240mg{\cdot}L^{-1}$으로 조절한 Hoagland 용액을 관비하였다. 식물체의 생육조사 및 무기원소 함량 분석은 양액처리 140일 후에, 근권부의 화학성 분석은 매 2주 간격으로 수행하였다. 유황의 시비수준이 증가할수록 모주의 전반적인 생장이 우수하였다. 엽록소 함량을 제외한 모주의 생장조사 항목에서 무처리구가 가장 저조하였고, $0.45g{\cdot}L^{-1}$ 이상의 세 처리구 간에서 통계적인 차이가 인정되지 않았다. 유황 처리수준이 높아질수록 런너 발생 및 자묘의 생장 역시 우수해지는 경향을 보였다. 런너 길이, 모주당 발생한 자묘수 및 1번 자묘의 생체중은 $0.45g{\cdot}L^{-1}$ 보다 낮은 유황처리구보다 0.90과 $1.80g{\cdot}L^{-1}$ 처리구가 우수하였지만 두 처리 간에는 통계적인 차이가 없었다. 유황 0과 $0.23g{\cdot}L^{-1}$ 처리구는 토양용액의 중탄산 농도와 pH가 지속적으로 상승한 반면 $0.90g{\cdot}L^{-1}$ 이상 처리구에서 다소 낮아지는 경향이었다. 토양용액 내 K과 $PO_4$의 농도는 0.90과 $1.80g{\cdot}L^{-1}$가 다른 처리구보다 낮았으며, Ca과 Mg의 농도는 처리구 간에 차이가 없었다. 유황 무처리구에서 분석한 무기원소 함량이 가장 적었으며, 유황 처리수준이 높아질수록 증가하였다. 이상의 결과, 코이어 더스트와 수피 혼합상토(5:5, v/v)에서 '싼타' 딸기를 수경재배할 때 양액의 중탄산 피해를 방지하고 식물 생육을 촉진시키기 위해서는 유황을 $0.90g{\cdot}L^{-1}$ 이상 기비처리하는 것이 효과적이라 판단하였다.