• Polymer(Korea)
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• v.25 no.6
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• pp.789-795
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• 2001

In order to recover nickel ion from waste water containing heavy metals, the PAN fibrous ion-exchanger with primary, secondary amine groups and carboxyl group was synthesized by acid and base hydrolysis. The hydrolysis yield of PAN fiber in acid solution was higher than base solution. The swelling ratio and ion-exchange capacity of PAN fiber which was synthesized in 1N $H_2SO_4$ solution at $80^{\circ}C$ for 7 hrs appeared 71.2% and 1.95 meq/g respectively. We investigated that the adsorption of nickel ion was approached 1.44 meq/g at 50 min and the maximum adsorption capacity of ion-exchanger was 2.48 meq/g. We confirmed that the $Ni^{+2}$ adsorption ability of the synthesized PAN fibrous ion-exchanger in this study is excellent.

• Journal of Life Science
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• v.15 no.1 s.68
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• pp.136-140
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• 2005

Microbial cell-based UV spectrometric assay for the quantitative measurement of epoxide hydrolase activity was evaluated and optimized for the efficient screening of whole cell activity of novel epoxide hydrolase. Epoxide hydrolase activity was determined by measuring the increase of the oxidized product, benzaldehyde. The effects of the concentrations of phenyl-1,2-ethanediol, sodium metaperiodate and cells were optimized for epoxide hydrolase-catalyzed hydrolysis of styrene oxide. The relevant kinetic parameters of Km and $V_{max}$ for the hydrolysis of (R)-styrene oxide by Rhodotorula glutinis were determined from Lineweaver-Burk plot as 41.2 nmol/min$\cdot$mg dcw and 7.5 mM respectively, and coincided well with those from GC analysis.

• Journal of Life Science
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• v.13 no.6
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• pp.794-798
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• 2003

Batch production of (S)-phenyl oxirane was investigated using epoxide hydrolase activity of Rhodosporidium toruloides SJ-4. Effect of reaction condition of asymmetric biohydrolysis of racemic phenyl oxirane was analyzed and optimized by response surface methodology. The optimal conditions of pH, temperature and DMSO cosolvent ratio were 7.4, $34^P\circ}C$, and 2.3%(v/v), respectively. The final yield was enhanced up to 67%, and reaction times required to reach 99% ee (enatiomeric excess) decreased down to 50% by response surface methodology Enantiopure (S)-phenyl oxirane with 100% enantiopurity and 24% yield (theoretical yield = 50%) was obtained from racemic substrate.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.417-426
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• 1997

Rice bran protein hydrolysates were prepared and some of their physicochemical properties were investigated to utilize rice bran as starting material for functional food ingredient. Rice bran proteins (RBP) were prepared from defatted rice bran by alkaline extraction and isoelectric precipitation. The enzyme for hydrolysis of RBP was selected through measuring relative activity by pH-drop method and comparing the degree of hydrolysis (DH) of hydrolysates. The enzymatic hydrolysates prepared by $Esperase^{\circledR}$ treatment were partitioned into two fractions by ultrafiltration(UF) with a 10 kDa molecular weight cut-off membrane. Each fraction was applied to a cholic acid-conjugated ${\omega}-aminohexyl$ Sepharose 4B column and the bile acid-binding components were obtained by eluting with deoxycholate. Gel permeation chromatography on a Sephadex G-50 column revealed that molecular weight of the bile acid-binding fraction of UF permeate was distributed in ranges of $2\;kDa{\sim}10\;kDa$ and $0.2\;kDa{\sim}0.6\;kDa$. Three peaks (R-1, R-2 and R-3) were obtained by prep-HPLC of bile acid-binding fraction of UF retentate and analyzed for total and free amino acid composition. The results showed that proline content of the bile-acid binding polypeptides and peptides was four times as much as that of rice bran protein and that the peak corresponding to higher average hydrophobicity had a higher free amino acid content. Average hydrophobicity slightly increased with enzymatic hydrolysis.

• Journal of Life Science
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• v.12 no.4
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• pp.423-426
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• 2002

Enantioselective resolution of racemic para-nitrostyrene oxide was investigated using epoxide hydrolase activity of Aspergillus niger LK for the production of optically pure (S)-para-nitrostyrene oxide. To overcome the poor solubility of the substrate, enantioselective hydrolysis in an organic solvent was attempted under optimized reaction conditions including reaction temperature and water content. (S)-para-Nitrostyrene oxide with high optical purity (> 99% ee) was obtained at 37% yield using fungal epoxide hydrolase-catalyzed enantioselective resolution.

• Clean Technology
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• v.7 no.4
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• pp.281-290
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• 2001

A microwave-assisted process to prepare chitosan from natural crabshells has been investigated. This study was primarily to examine the effectiveness of microwave as clean energy for chitosan preparation. Several human-edible organic acids were used as clean catalyst, possibly to improve the current HCl-based hydrolysis process of polymeric chitosan. The microwave was found to be effective substantially in reducing the reaction time. Nonetheless, no beneficial effect of microwave other than time, such as the chemical selectivity, was hardly observed. The organic acids were very effective in the hydrolysis reaction of polymeric chitosan. Their catalytic behavior was greatly improved especially when reactions were performed under pressure. In the case of autoclave reaction for 60 minutes at $120^{\circ}C$, viscous solution of polymeric chitosan (mol. wt. > 300,000) turned into thin solutions of water-like viscosity, which means chitosan molecules were decomposed to very small-sized oligomers.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.155-156
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• 2001

최근 수산물이 인체에 미치는 영양 및 건강효과로 어류소비량은 전세계적으로 매년 2.5％정도 증가하고 있으며 이중 양식어류가 26％을 차지하고 있고 수요량은 계속 증가 추세에 있다. 그러나 환경오염 및 각국의 경제수역 설정으로 어획량은 감소하고 있으며, WTO 출범 이후 세계적으로 자국의 자원량 확보나 미이용자원의 활용에 많은 심혈을 기울이고 있다. 양식생산량 증대와 더불어 양어사료 생산량도 계속 증가하고 있으며, 사료는 양식산업 경비의 30-50％를 차지한다. (중략)

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.218-226
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• 2007

The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.647-661
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• 2005

The stereoselective synthesis of chiral terminal epoxide is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this review, we investigate the research and development trend in the asymmetric ring opening reactions using cobalt salen catalysts. Hydrolytic kinetic resolution (HKR) technology is the very prominent way to prepare optically pure terminal epoxides among available methods. We have synthesized homogeneous and heterogeneous chiral dinuclear salen complexes and demonstrated their catalytic activity and selectivity for the asymmetric ring opening of terminal epoxides with variety of nucleophiles and for asymmetric cyclization to prepare optically pure terminal epoxides in one step. The resolved ring opened product combined with ring closing in the presence of base and catalyst afforded the enantioriched terminal epoxides in quantitaive yield. Potentially, these catalysts are using on an industrial scale to produce chiral intermediates. The experimental results of HKR technology applied to the synthesis of various chiral compounds are presented in this paper.

• The Microorganisms and Industry
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• v.20 no.1
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• pp.23-27
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• 1994

본고에서는 화학적수법으로 다양한 특이한 기질을 제조하여 여기에 입체특이적 성질(stereospecificity)과 입체선택적 성질(steroselectivity)이 높은 생물학적 방법들 중에서 주로 lipase를 이용한 부제가수분해반응(asymmetric hydrolysis)과 그 역반응인 에스테르화반응(esterification)등을 도입한 chiral building block의 제조와 이를 이용한 곤충 생리활성물질인 pheromone의 합성에 대한 최근의 많은 예들중 상품화를 시도하고 있는 매미나방의 pheromne인 (+)-disparlure에 대하여 간단히 소개하고자 한다.