• 한국환경농학회지
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• 제30권3호
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• pp.346-356
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• 2011

BACKGROUND: Chemical fungicides not only may pollute the ecosystem but also can be environmentally hazardous, as the chemicals accumulate in soil. Biological control is a frequently-used environment-friendly alternative to chemical pesticides in phytopathogen management. However, the use of microbial products as fungicides has limitations. This study isolated and characterized a three-antifungal-enzyme (chitinase, cellulase, and ${\beta}$-1,3-glucanase)-producing bacterium, and examined the conditions required to optimize the production of the antifungal enzymes. METHOD AND RESULTS: The antifungal enzymes chitinase, cellulase, and ${\beta}$-1,3-glucanase were produced by bacteria isolated from an sawmill in Korea. Based on the 16S ribosomal DNA sequence analysis, the bacterial strain AM50 was identical to Streptomyces sp. And their antifungal activity was optimized when Streptomyces sp. AM50 was grown aerobically in a medium composed of 0.4% chitin, 0.4% starch, 0.2% ammonium sulfate, 0.11% $Na_2HPO_4$, 0.07% $KH_2PO_4$, 0.0001% $MgSO_4$, and 0.0001% $MnSO_4$ at $30^{\circ}C$. A culture broth of Streptomyces sp. AM50 showed antifungal activity towards the hyphae of plant pathogenic fungi, including hyphae swelling and lysis in P. capsici, factors that may contribute to its suppression of plant pathogenic fungi. CONCLUSION(S): This study demonstrated the multiantifungal enzyme production by Streptomyces sp. AM50 for the biological control of major plant pathogens. Further studies will investigate the synergistic effect, to the growth regulations by biogenic amines and antifungal enzyme gene promoter.

• 한국해안·해양공학회논문집
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• 제32권1호
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• pp.26-38
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• 2020

설계파고 추정에 사용한 AM 자료의 IID 가정에 대한 검정을 수행하였다. 검정은 독립 검정, 분포 차이 검정으로 구분하고, 각각의 검정은 태풍, 비태풍 조건에서의 연안 격자, 연안 내부격자 각각 210개, 310개 지점의 AM 자료 세트를 대상으로 수행하였다. 독립 검정 결과, 비태풍, 태풍 자료 세트에 대하여 각각 1.8~5.3%, 1.4~6.0% 범위의 기각 비율을 보여, 대부분의 자료가 독립 검정을 만족하는 것으로 파악되었다. 한편 태풍 자료와 비태풍 자료의 분포 차이 검정은 연안 격자와 연안 내부격자 모두 검정 방법에 따라 47~79% 범위로 동일분포 가설이 기각되는 것으로 파악되었다. 따라서 극치해석에 의한 설계파고 추정에서 두 자료를 구분하여 각각 설계파고를 추정하는 과정이 적절하다.

• Food Science and Biotechnology
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• 제18권4호
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• pp.895-899
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• 2009

A new approach for the determination of acrylamide (AM) in foods by solid phase microextraction-gas chromatography (SPME-GC) was established. AM was bromized and transformed to 2-bromoacrylamide (2-BAM). 2-BAM was then extracted by a commercial SPME fiber, $75-{\mu}m$ Car/PDMS fiber, for GC detection. The influence of extraction and desorption parameters such as extraction temperature and time, stirring rate, desorption temperature, and time were studied and optimized. The mass concentration was proportional to the peak area of 2-BPA from 1.0 to 8,000 ${\mu}g/L$. The detection limit of the SPME-GC for 2-BAM was found to be 0.1 ${\mu}g/L$, and the recoveries and relative standard deviations for different food samples were 74.5 to 102.0%, and 4.2 to 9.1%, respectively. The presented method was applied to the determination of AM in fried foods.

• Tuberculosis and Respiratory Diseases
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• 제43권6호
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• pp.954-964
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• 1996

배경: 미만성 간질성 폐질환(DILD)들은 처음에 폐포염(alveolitis) 으로 시작해 섬유화로 진행하여 심한 폐기능장애를 초래하는 질병군들로서 병의 종류에 따라 침윤되는 염증세포들의 종류에 차이가 있다. 근래에 염증세포들의 침윤을 유도하는 화학주유물질들(chemokine)이 많이 발견되었는데 이들은 화학구조에 따라 C-X-C형과 C-C형으로 분류되며, 구조만 다를 뿐 아니라 작용하는 세포도 차이가 있기 때문에 주로 분비되는 화학주유물질의 종류에 따라 폐포염의 종류가 결정이될 가능성이 많다. 이에 연구자들은 폐포염과 화학주유물질과의 연관성 및 폐포대식세포 (AM)가 이들 화학주유물질의 주 근원이 되는가를 알아보기 위하여 DILD 환자들에서 cytokine을 분비하여 발병기 전에 주작용을 한다고 알려진 AM 에서의 C-X-C 형 IL-8 과 C-C 형인 MIP- 1 ${\alpha}$ 의 분비 및 BAL액내에서의 이들 화학주유물질들의 농도를 폐포염의 양상을 잘 반영한다고 알려진 BAL 액내 세포양상과 비교분석 하였다. 대상및 방법: 대상은 임상소견과 조직검사로 확진된 lPF 환자 10명, 교원성질환과 연관된 폐섬유증 환자 4명, 폐유육종중 10명과 과민성폐장염 환자 2명, 총 26명과 정상 대조군 7명이었고, 이들에서 BAL을 시행하여 그 세포구성의 변화를 관찰하고, AM을 분리배양하여 그 상청액및 BAL액에서 의 IL-8과 MIP- 1 ${\alpha}$ 의 농도를 ELISA 방법으로 측정하여 비교 분석하였다. 결과: AM 에서의 IL-8 분비는 DILD 환자들에서 $8.15{\pm}4.58$ ng/ml로 정상 대조군 ($1.10{\pm}0.93$ ng/ml)보다 유의하게 (p=0.0003) 증가하였고, AM에서 분비된 IL-8 량은 BAL액내 총세포수와 (r=0.484, p=0.0068), 또 BAL액내 dla파구의 백분률 (r=0.592, p=0.0004)및 임파구의 수효 (r=0.516, p=0.0042), AM의 백분플 (r=-0.505, 0.0032) 과 유의한 상관관계를 보여 주었다. AM에서의 MIP- 1 ${\alpha}$ 분비는 DILD환자군에서 ($2.41{\pm}1.45$ ng/ml) 정상인보다 ($0.63{\pm}0.30$ ng/ml, p=0.0031) 유의하게 증가되었으나, MIP- 1 ${\alpha}$ 의 분비량은 BAL액내 총세포수와 r=0.368, p=0.0456로 유의한 상관관계를 나타내었고, AM의 수효와 연관이 있는 경향을 (r=0.356, p=0.0579) 보어 주었을 뿐이었다. BAL 액내의 IL-8 농도는 DILD 환자군에서 ($40.4{\pm}34.5$ pg/ml)로 정상인의 $3.90{\pm}2.47$ pg/ml보다 높았고 (p=0.0094), IL-8 농도와 BAL 액내 총 세포수(r=0.484, p=0.0068), AM의 백분율(r=-0.505, p=0.0032), 임파구의 백분율 (r=0.592, p=0.0004) 및 임파구의 수효 (r=0.516, p=0.0042) 와 좋은 상관관계를 나타내어 IL-8 이 폐내 침윤된 염증세포의 종류를 결정하는데 중요한 역할을 하는 것을 시사하였다. 그러나 BAL액내 MIP- 1 ${\alpha}$ 의 농도는 정상인과 차이가 없었다. 결론: 이상의 결과로 미루어 IL-8과 MIP- 1 ${\alpha}$ 모두가 DILD의 발병기전에 작용하나, IL-8 이 폐포염의 양상을 결정하는데 더 중요한 역한을 하는 것으로 추측되었다.

• Bulletin of the Korean Chemical Society
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• 제13권1호
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• pp.32-36
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• 1992

The gas-phase pyrolysis reactions of 2-alkoxypyrimidines(II), 2-alkoxypyrazines(III), 4-ethoxypyrimidine(IV) and 3-ethoxypyridazine(V) are investigated theoretically using the AM1 MO method. These compounds pyrolyze in a concerted retro-ene process with a six-membered cyclic transition state (TS). The relative order of reactivity if (IV)>(II)>(III)>(V), which can be rationalized by the two effects arising from electron-withdrawing power of the aza-substituent: (ⅰ) Electron withdrawal from the C-O bond accelerates the rate and (ⅱ) electron withdrawal from the $N^1$-atom, that is participating in the six-membered TS, deactivates the reaction. We are unable to explain the experimental result of the greatest reactivity for pyridazine, (V), with our AM1 results. The reactivity increase accompanied by successive methylation of the ethoxy group, ethoxytert-butoxy, is due to a release of steric crowding in the activation process.

• Journal of Microbiology and Biotechnology
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• 제20권9호
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• pp.1276-1282
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• 2010

In traditional mixotrophic cultures of microalgae, all the inorganic nutrients and organic carbon sources are supplied in the medium before inoculation. In this study, however, an alternative approach was adopted in Haematococcus pluvialis Flotow, a microalga capable of growing mixotrophically on sodium acetate (Na-Ac). First, the cells were grown under 75 ${\mu}Mol$ photons $m^{-2}s^{-1}$ phototrophically without Na-Ac until the stationary phase and then exposed to five different light regimes by the addition of Na-Ac (e.g., dark, 20, 40, 75, and 150 ${\mu}Mol$ photons $m^{-2}s^{-1}$). Dry weight (DW), pigments, and especially cell number in alternative mixotrophy (AM) were higher than traditional mixotrophy (TM). Cell number in AM almost doubled up from 21.7 to $42.9{\times}10^4$ cells/ml during 5-day exposure to Na-Ac, whereas the increase was only 1.2-fold in TM. Maximum cell density was reached in 75 ${\mu}Mol$ photons $m^{-2}s^{-1}$ among the light intensities tested. We propose that Na-Ac in TM of H. pluvialis can not be utilized as efficiently as in AM. With this respect, AM has several advantages against TM such as a much higher cell density in a batch culture period and minimized risk of contamination owing to the shorter exposure of cells to organic carbon sources. In consequence, this method may be used for other strains of the species, and even for the other microalgal species able to grow mixotrophically.

• 한국미생물·생명공학회지
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• 제36권3호
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• pp.227-232
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• 2008

고추 역병이 발병된 토양 시료에서 길항미생물을 선발 및 개량하여 다시 현장에 적용했을 때 방제능 및 적응력이 높은 생물 방제균을 선발하고자 총 300여점의 경북 북부지역의 토양시료로부터 길항능이 우수한 균주를 분리하였으며, 이들을 대상으로 고추 역병균에 대한 항진균력이 가장 우수한 균주 AM-651을 최종 선발하였다. 분리균주 AM-651은 생리생화학적 특성과 16S rDNA sequencing의 방법을 이용하여 동정한 결과 Bacillus sp.로 동정되었다. 항진균성 활성물질의 생산을 위한 배지의 최적조건은 Davis minimal media를 변형하여 배양하였을 경우 pH 7, 온도 $30^{\circ}C$ 조건에서 고추 역병균에 대한 항진균 활성이 높았으며, 탄소원으로는 0.5% glucose, 질소원으로는 0.1% $(NH_4)_2SO_4$, 무기염으로는 0.7% $K_2HPO_4$를 첨가하였을 때 가장 높은 활성을 보였다 선발된 Bacillus sp. AM-651 균주를 시간대별로 배양 후 항진균력을 측정 해 본 결과 48시간 배양액에서 고추 역병균에 대한 억제율이 가장 높았다. 또한, Bacillus sp. AM-651의 배양액은 pH와 온도의 변화에서 안정된 활성을 보였다. Bacillus sp. AM-651은 고추 역병 외에도 B. sorokiniana, B. cinerea, R. solani 등에 대하여 항진균 활성이 높았고, 다른 식물성 병원균에 대해서도 비교적 항진균 활성이 높게 나타났다. 열처리한 Bacillus sp. AM-651 배양상등액은 처리전과 비슷한 항진균 활성을 가지므로 열에 안정한 물질인 것으로 추측되었다.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.85-93
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• 2015

Background: $^{241}Am$, $^{243}Am$, and $^{237}Np$ isotopes are among the most radiotoxic components of spent nuclear fuel. Recently, researchers have planned different incineration scenarios for the highly radiotoxic elements of nuclear waste in critical reactors. Computational methods are widely used to predict burnup rates of such nuclear wastes that are used under fuel matrixes in critical reactors. Methods: In this work, the Monte Carlo N-particle transport code was used to calculate the neutronic behavior of a transuranic (TRU)-bearing CANada Deuterium Uranium 6 reactor. Results: The computational data showed that the 1.0% TRU-containing thorium-based fuel matrix presents higher proliferation resistance and TRU depletion rate than the other investigated fuel Matrixes. The fuel matrix includes higher negative temperature reactivity coefficients as well. Conclusion: The investigated thorium-based fuel matrix can be successfully used to decrease the production of highly radiotoxic isotopes.

• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.42-48
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• 1999

We have performed a quantum-chemical investigation on the conformations and electronic properties of a variety of methoxy-substituted poly(p-phenylenevinylenes) (PPVs) to elucidate the effects of alkoxy substitution. Geometrical parameters for the polymers were fully optimized through Austin Model I (AM I) semi-empirical Hartree-Fock (HF) band calculations. Electronic properties of the polymers were obtained by applying the AM I optimized structures to the modified extended Huckel method. To confirm validity of the AM I conformational results, we also carried out ab initio HF calculations with the 6-31G (d) basis set for a variety of methoxy-substituted divinylbenzenes. It is found that the potential energy surfaces of alkoxy-substituted PPVs are quite shallow around the planar conformations, suggesting that the prepared films possess a variety of conformations with different torsion angle in the solid state, depending on the synthetic conditions. When two alkoxy groups are concurrently substituted at the adjacent sites in the phenylene ring, these groups are subject to rotating around the C(sp2)-O bonds by 70-80° to avoid the strong steric repulsion between them. Consequently, the overlap between the π-type p orbital of oxygen and the π molecular orbitals of the polymer decreases. This leads to a wide gap and a high oxidation potential for tetramethoxy-substituted PPV, compared to those of dialkoxy-substituted PPV.

• Bulletin of the Korean Chemical Society
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• 제11권3호
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• pp.194-200
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• 1990

Various mechanistic aspects of the A2 hydrolysis of methyl acetimidate were explored using the MNDO method. As in thecorresponding reactions of acetamide and methyl carbamate, a proton transfer pre-equilibrium exists between the N-protonated and the O-protonated tautomers, and the subsequent hydrolysis proceeds from the more stable N-protonated form. Of the two reaction pathways, the $A_{AL}2$ path is favored in the gas phase and in concentrated acid solutions, whereas the $A_{AC}2$ path is favored in less acidic solutions with a stable cationic tetrahedral intermediate formed in the rate determining step. Negative charge development on the alkoxy oxygen in the transition state suggested a rate increase with the increase in the electron withdrawing power of the alkoxy group. Calculations on the reaction processes with AM1 indicated that MNDO is more reliable in this type of work, although AM1 is better than MNDO in reproducing hydrogen bonds.