• 대한화학회지
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• 제57권6호
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• pp.703-711
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• 2013

In the present investigation, kinetic studies of oxidation of formic acid with and without catalyst and promoter in aqueous acid media were studied under the pseudo-first order conditions [formic acid]T ${\gg}[Cr(VI)]_T$ at room temperature. In the 1,10-phenanthroline (phen) promoted path, the cationic Cr(VI) phen complex is the main active oxidant species undergoes a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through several steps leading to the products $CO_2$ and $H_2$ along with the Cr(III) phen complex. The anionic surfactant (i.e., sodium dodecyl sulfate, SDS) and neutral surfactant (i.e., Triton X-100, TX-100) act as catalyst and the reaction undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Whereas the cationic surfactant (i.e., N-cetyl pyridinium chloride, CPC) acts as an inhibitor restricts the reaction to aqueous phase. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. The neutral surfactant TX-100 has been observed as the suitable micellar catalyst for the phen promoted chromic acid oxidation of formic acid.

• 한국균학회지
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• 제31권3호
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• pp.168-174
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• 2003

C. militaris 균사를 콜로이달 키틴이 첨가된 액체 배지에서 배양한 후 황산암모늄 분별침전, 이온 교환 및 겔 여과 크로마토그래피를 이용하여 배양액 중의 chitianse를 분리 정제하였다. 이 효소의 최적 pH와 온도는 각각 5.5와 $35^{\circ}C$이었으며 겉보기 분자량은 48.5 kDa이었고, 그 Km 값은 0.57 mM이었다. 이 효소는 $Cu^{2+},\;Mn^{2+},\;Hg^{2+},\;Zn^{2+},\;CO_{3}^{2-},\;SO_4^{2-},\;CN^-$ 및 OCN^-$ 이온에 의하여 활성이 억제되었으나, $Mg^{2+}$ 및 $K^+$ 이온에 의하여 활성이 약간 증가되었다. 또한 효소 단백질의 아미노산 잔기와 선택적으로 반응하는 무수말레인산, 무수아세트산 및 N-bromo succinimide에 의하여 84.0% 활성이 억제되어 카르복실기를 가진 아미노산 잔기가 이 효소의 활성 부위에 중요한 역할을 함을 알았다. NAG6에 의한 기질 분해 특이성 실험을 통하여 이 효소는 endo-형태의 chitinase임을 알았다.

• 한국식품영양과학회지
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• 제38권6호
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• pp.801-806
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• 2009

본 연구는 transglutaminase 생산능이 우수한 토양유래방선균 strain YK-2를 TGase 최적생산배지에서 $28^{\circ}C$, 5일간 배양하여 얻은 배양여액으로 본 효소의 정제 및 정제된 효소의 효소화학적 특성에 관하여 검토한 것이다. 본 효소의 정제는 50% methanol precipitation, DEAE-Sephadex column chromatography의 정제 절차를 거쳐 56.5%의 수율로 정제되었고, 정제된 효소의 순도는 12.5% SDS-PAGE에서 단일 밴드를 나타내어, 서브유닛트의 분자량이 약 45,000 dalton으로 추정되는 호모형 효소인 것을 알 수 있었다. 정제된 TGase의 생화학적 제 특성을 검토한 결과, 등전점은 pH $6.0{\sim}7.0$ 부근에 있는 것으로 나타났으며, 본 효소의 기질인 CBZ-L-Gln-Gly 농도에 대한 Km치는 18.5 mM으로 추산되었다. 또한 금속이온 및 저해제의 영향으로는 $Hg^{++}$에 의해서 본 효소의 활성이 강하게 저해되었으나, DTT 및 mercaptoethanol에 의해 각각 293% 및 219% 활성이 증가하였다.

• 미생물학회지
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• 제8권1호
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• pp.41-51
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• 1970

S.albus subsp.와 S.globosus에서 Tetracyclin과 Streptomycin 같은 항생물질을 생성된다는 것은 이미 전보에서 밝힌 바 있다. 이들 두 種의 생장최적조건과 항생제 생성정도와의 관계를 배지성분과 그 농도에 따라 검토하였다. 그 결과 S.albus subsp.와 S.globosus 모두 배양시간이 130~150시간이 될때 항생물질 생성과 균체량이 최고에 달했다. 그리고 PH는 그 근처에서만 떨어지는 현상을 볼 수 있었다. 또한 두 균주 모두 탄소원으로서는 starch(4~5%)질소원으로서는 soybeam meal(1.5~2.0%)에서 균체의 생장도 양호하고 향균력도 높게 나타났다. 이외의 성분으로는 calcium carbonate(2mg/ml), potassium phosphate' dibasic(0.05M~0.01M), magnesium sulfate(0.01M~0.03M) ferric chloride(0.01M)가 가장 생장에 좋은 배지농도로 추정되며 zinc ion(0.0005M)은 균체생장을 현저하게 억제하였다.

• Advances in nano research
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• 제8권1호
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• pp.1-11
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• 2020

In order to develop a new adsorbent for removal of formaldehyde from aqueous solution, surface modification of TiO₂ nanoparticles was performed with 2,4-Dinitrophenylhydrazine (DNPH) that have a strong affinity to the formaldehyde. Sodium dodecyl sulfate (SDS) surfactant was used to improve the DNPH grafting to TiO₂ surface. Modified adsorbents were characterized by SEM, TEM, XRD, EDX and FTIR. Since the COD level in wastewaters including formaldehyde is considerable, it is necessary to determine the COD content of the synthetic wastewater. In order to determine the optimal removal conditions, the effect of contact time (60-210 min), pH (4-10) and adsorbent dosage (0.5-1.5 g/L) on adsorption and COD removal efficiencies were studied, using response surface method. EDX and FTIR analysis confirmed the presence of nitrogen-containing functional groups on the modified TiO₂ surface. The maximum formaldehyde adsorption and COD removal efficiencies by modified TiO₂ were about 15.65 and 7.35% higher than the unmodified nanoparticles respectively. Therefore, the grafting of nano-TiO₂ with DNPH would greatly improve its formaldehyde adsorption efficiency. The optimum conditions determined for a maximum formaldehyde removal of 99.904% and a COD reduction of 94.815% by TiO₂/SDS/DNPH nanocomposites were: adsorbent dosage 1.100 g/L, pH 7.424 and the contact time 183.290 min.

• 대한금속재료학회지
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• 제49권1호
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• pp.79-84
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• 2011

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at $380^{\circ}C$ for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

• Parasites, Hosts and Diseases
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• 제60권5호
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• pp.345-352
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• 2022

Chitinase AO-801 is a hydrolase secreted by Arthrobotrys oligospora during nematode feeding, while its role remained elusive. This study analyzed the molecular characteristics of recombinant chitinase of Arthrobotrys oligospora (reAO-801). AO-801 belongs to the typical glycoside hydrolase 18 family with conserved chitinase sequence and tertiary structure of (α/β)₈ triose-phosphate isomerase (TIM) barrel. The molecular weight of reAO-801 was 42 kDa. reAO-801 effectively degraded colloidal and powdered chitin, egg lysate, and stage I larval lysate of Caenorhabditis elegans. The activity of reAO-801 reached its peak at 40℃ and pH values between 4-7. Enzyme activity was inhibited by Zn2⁺, Ca2⁺, and Fe3⁺, whereas Mg2⁺ and K⁺ potentiated its activity. In addition, urea, sodium dodecyl sulfate, and 2-mercaptoethanol significantly inhibited enzyme activity. reAO-801 showed complete nematicidal activity against C. elegans stage I larvae. reAO-801 broke down the C. elegans egg shells, causing them to die or die prematurely by hatching the eggs. It also invoked degradation of Haemonchus contortus eggs, resulting in apparent changes in the morphological structure. This study demonstrated the cytotoxic effect of reAO-801, which laid the foundation for further dissecting the mechanism of nematode infestation by A. oligospora.

• 자원리싸이클링
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• 제31권5호
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• pp.3-19
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• 2022

전기막(Electro-membrane) 기술은 전기투석(ED) 및 바이폴라 전기투석(BMED)과 같이 선택적 투과성을 갖는 이온교환막을 사용하여 전기에너지에 의하여 수용액 내의 물질을 분리·정제하는 공정이다. 전기막(Electro-membrane) 기술은 공정 중에 부산물이 발생하지 않고 회수된 염기나 산을 공정 중에 재사용할 수 있어 환경 친화적인 기술로 주목받고 있다. 본고에서는 전기분리막 기술인 ED와 BMED 기술의 원리 및 셀(Cell) 구성에 따른 여러 가지 특성 및 문제점 등에 대해 조사하고, 특히 금속회수 공정 중 다량 발생되고 있는 황산나트륨(Na2SO4) 폐액 처리와 관련된 연구사례들을 조사·분석하였다.

• Journal of the Korean Wood Science and Technology
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• 제47권2호
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• pp.163-177
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• 2019

폐MDF로부터 해섬하여 얻은 재생섬유를 Reactive Red H-E3B (Bis-monochlorotriazine(MCT)/MCT type)와 Reactive Red RB 133%(bis-monochlorotriazine/Vinyl sulphone type)로 염색할 때 최적의 염색조건을 구명하기 위하여 염색조건(염료 농도, 염과 알칼리 첨가량, 염색온도)과 염색특성 및 일광견뢰도와의 관계를 검토하였다. 2종의 반응성염료 모두 염료농도가 1~10(%,OWF)로 증가함에 따라 염착량(K/S)은 증가하였다. 또한, H-E3B가 RB 133%보다 염료 농도에 관계없이 K/S는 높았으며, 자외선 조사에 따른 색차는 낮아 자외선에 의한 변색 저항성이 양호하였다. 황산나트륨의 첨가량이 증가할수록 색차 및 K/S도 증가하였으며, 염의 첨가량은 50~70 g/L가 적절하였다. 2 g/L의 탄산나트륨 첨가에 의해 색차 및 K/S가 크게 증가하였으나 그 이상의 첨가량 증가에서는 거의 차이가 없었다. 탄산나트륨의 첨가량은 pH 10을 유지하는 5~10 g/L가 적절할 것으로 생각된다. H-E3B 염료는 염색 온도가 높아짐에 따라 염착량이 증가하다가 $80^{\circ}C$에서 다시 감소한 반면 RB 133%는 $60{\sim}70^{\circ}C$까지는 거의 동일한 염착량을 나타냈으나, 이후 감소하였다. 따라서 H-E3B는 $80^{\circ}C$, RB 133%는 $60^{\circ}C$가 적정한 것으로 판단된다. 이상의 최적조건에서 폐MDF 목질섬유를 염색처리하면 H-E3B염료는 1.5~2.0R, RB 133%염료는 9.6~10.0 PR의 색상을 가지는 염색 재생 목질섬유의 제조가 가능하였다.

• Journal of Microbiology and Biotechnology
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• 제15권6호
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• pp.1330-1336
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• 2005

Polyhydroxyalkanoic acid (PHA) inclusion bodies were analyzed in situ by $^{13}C$-nuclear magnetic resonance ($^{13}C$-NMR) spectroscopy. The PHA inclusion bodies studied were composed of poly(3-hydroxybutyrate) or poly(3hydroxybutyrate-co-4-hydroxybutyrate), which was accumulated in Hydrogenophaga pseudoflava, and medium-chain-length PHA (MCL-PHA), which was accumulated in Pseudomonas fluorescens BM07 from octanoic acid or 11-phenoxyundecanoic acid (11-POU). The quantification of the $^{13}C$-NMR signals was conducted against a standard compound, sodium 2,2-dimethyl-2-silapentane-5-sulfonate (DSS). The chemical shift values for the in vivo NMR spectral peaks agreed well with those for the corresponding purified PHA polymers. The intracellular degradation of the PHA inclusions by intracellular PHA depolymerase(s) was monitored by in vivo NMR spectroscopy and analyzed in terms of first-order reaction kinetics. The H. pseudoflava cells were washed for the degradation experiment, transferred to a degradation medium without a carbon source, but containing 1.0 g/l ammonium sulfate, and cultivated at $35^{\circ}C$ for 72 h. The in vivo NMR spectra were obtained at $70^{\circ}C$ for the short-chain-length PHA cells whereas the spectra for the aliphatic and aromatic MCL-PHA cells were obtained at $50^{\circ}C\;and\;80^{\circ}C$, respectively. For the H. pseudoflava cells, the in vivo NMR kinetics analysis of the PHA degradation resulted in a first-order degradation rate constant of 0.075/h ($r^{2}$=0.94) for the initial 24 h of degradation, which was close to the 0.050/h determined when using a gas chromatographic analysis of chloroform extracts of sulfuric acid/methanol reaction mixtures of dried whole cells. Accordingly, it is suggested that in vivo $^{13}C$-NMR spectroscopy is an important tool for studying intracellular PHA degradation in terms of kinetics.