• Applied Biological Chemistry
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• v.31 no.4
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• pp.376-381
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• 1988

The optimal reaction conditions were investigated to produce L-phenylalanine from transcinnamic acid and ammonia by Rhodotorula glutinis IFO 0559. The highest amount of L-phenylalanine was produced when the reaction mixture containing 200mM of traps-cinnamic acid, 4M of $NH_4OH$, 250mM of $(NH_4)_2SO_4$, 0.005% of cetylpyridinium chloride (pH 10.5) and 50mg/ml of dry cell was used. Among the nonaqueous organic solvents, petroleum ether was the most effective on the production of L-phenylalanine. The optimal concentration of petroleum ether in the reaction mixture was 50%. Under the optimal conditions, 21.1g/l of L-phenylalanine was produced in 12hr, and the yield was 63.9% based on transcinnamic acid.

• The Korean Journal of Food And Nutrition
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• v.14 no.2
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• pp.120-125
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• 2001

The inhibitory effects of xanthine oxidase by the methanol extract and the solvent fractions obtained from persimmon leaves were investigated. The inhibition ratio of xanthine oxidase was 78% by addition of 2.0mg/ml of the methanol extract. Among the solvent fractions, the ethylacetate fraction showed the strongest inhibitory effect against the xanthine oxidase, followed by the hexane fraction. The effect increased with addition of the ethylacetate fraction. At a concentration of 2.0mg/ml of the ethylacetate fraction, 65% of the enzyme activity decreased within 1.0 min of incubation with xanthine oxidase. But the activity of xanthine oxidise did not decrease significantly by the length of the incubation time.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.528-535
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• 1988

The rates of oxygen ring formation of $[Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ have been investigated spectrophotometric method in binary aqueous mixtures. Temperature was $20^{\circ}C$ to $40^{\circ}C$ and pressure was varied up to 1500 bar. The observed rate constants are increased by hydrogen ion and decreased by thiocyanate. The more increasing of co-solvents dielectric constant, the more stable intermediate is formed. The observed rate constant is given by, $k_{obs}^{-1} = k^{-1} (1 + K^{-1}[H_2O]^{-1}) All activation parameters are positive values. The oxygen ring formation of [Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ is believed to be a interchange-dissociative mechanism..

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.624-628
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• 1998

The aromatic organic solvents(BTX) were decomposed in the fixed bed reactor packed with a 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst, then, supercritical carbon dioxide(SC-$CO_2$) was used as the reaction media. And the conversion was dependent on the inlet concentration of BTX and the molar density of SC-$CO_2$. The conversion of BTX was decreased with increasing of inlet concentration, and was increased with temperature and pressure. The maximum conversion of benzene was 98.5% at $300^{\circ}C$ and 204.1 atm, and that of toluene and xylene were 82.0 and 76.5%, respectively, at $350^{\circ}C$ and 204.1 atm. The intermediate products of partial oxidation were identified as benzaldehyde, phenol, benzenemethanol, and so on. The BTX can be effectively converted into harmless $CO_2$ and $H_2O$ at appropriate operating condition. Thus, the nontoxic recovery process was suggested as the removal method of BTX.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.599-603
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• 2012

The enantioselective hydrolysis of racemic styrene oxide in organic solvents was conducted using a recombinant E. coli expressing protein-engineered Mugil cephalus epoxide hydrolase (McEH). The volumetric total activity of the recombinant E. coli was enhanced 2.2-fold by IPTG induction at a mid-exponential growth phase. Among organic solvents with different log P values, isooctane was chosen based on the high activity and the enantioselectivity of McEH. Some lyoprotectants such as skim milk or sucrose enhanced the McEH activity. Enantiopure (S)-Styrene oxide with a 98% ee was obtained from the racemic styrene oxide with a 53.6% yield based on its theoretical yield in isooctane.

• Journal of Life Science
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• v.25 no.12
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• pp.1458-1469
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• 2015

Many organic solvent-tolerant bacteria have been isolated from all environments such as soil, waste-water, even deep sea after first isolation report of organic solvent-tolerant bacterium. Most organic solvent- tolerant isolates have been determined to be Gram-negative bacteria, because Gram-negative bacteria have inherent tolerance property toward hostile organic solvents more than Gram-positive bacteria. The mechanisms of organic solvent tolerance have been elucidated extensively using mainly organic solvent-tolerant Gram-negative bacteria. The solvent-tolerance mechanisms in Gram-positive bacteria can be found in comparatively recent research. Organic solvents exhibited different toxicity depending on the solvent, and the tolerance levels of organic solvent-tolerant bacteria toward organic solvents were also highly changeable among species and strains. Therefore, organic solvent-tolerant bacteria could coped with solvent toxicity and adapted to solvent stress through the multifactorial and multigenic adaptative strategies. They could be survived even in the hyper concentrations of organic solvents by mechanisms which include: changes in cell morphology and cell behaviour, cell surface modifications, cell membrane adaptations, solvent excretion pumps, chaperones and anti-oxidative response. The aim of this work is to review the representative solvent tolerant bacteria and the adaptative and tolerance strategies toward organic solvents in organic solvent-tolerant bacteria, and their potential industrial and environmental impact.

• Journal of the Korean Chemical Society
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• v.41 no.1
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• pp.22-46
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• 1997

Kinetic studies on nucleophilic substitution reaction of phenacyl bromide and phenacyl chloride with pyridines were conducted at 25℃ and 35℃ in methanol-acetonitrile solvents mixtures. It was shown that the reaction proceeds via an SN2 reaction mechanism based on the transition state parameters, ΔH≠ and ΔS≠ and Bro nsted β values. Quantum mechanical model predicted a product-like transition state, where bond-formation is much more progressed than bond breaking, upon changing the leaving group to that with a better leaving ability.

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.406-410
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• 1973

Kinetic study of halide exchange for dimethylsulfamoyl chloride in dry acetone by using radioisotopic halide ions has been carried out at two temperatures. The result of the order of nucleophilicity, as compared with benzenesulfonyl chloride, shows a similar tendency but reaction rate is slower, more than $10^{-2}$times, than benzenesulfonyl chloride. The activation parameter, ${\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$ decrease in sequence $Cl^-\;>\;Br^-\;>\;I^-$ in dimethylsulfamoyl chloride but it is the reverse order found for benzenesulfonyl chloride. The results are interpreted with bond-breaking, bond-formation, and electronic requirments, and in the light of HSAB Principle.

• Polymer(Korea)
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• v.36 no.1
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• pp.98-103
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• 2012

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized using $Cu(NO_2)_2{\cdot}3H_2O$ or CuCl catalyst with various amounts of ligand and base in several different solvent systems. CuCl/1-methylimidazole/ammonium hydroxide was found to be an effective catalyst system which showed the highest polymer yield and molecular weight. The effects of catalyst/monomer ratio, different amine ligands, and the content of mono-functional reagent 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated. Among the co-solvent systems used in this polymerization, chloroform/methanol 9/1(v/v) gave the highest polymer yield and molecular weight ($\overline{M_n}$ 55 K, $\overline{M_w}$ 92 K, PDI 1.7). The catalytic activity between CuCl and CuI was compared by oxygen-uptake experiments and the formation of sideproduct, 5,5'-tetramethyl-4,4'-diphenoquinone (DPQ), was analyzed by ultraviolet spectroscopy.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.863-870
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• 1999

The catalytic performance of Co-Mn-Br system was performed in the 2,6-dimethylnaphthalene(DMN) oxidation at relatively mild reaction conditions such as $160^{\circ}C$ and $6kg/cm^2$. Experiments were conducted using a $2{\ell}$ batch reactor with varying the concentrations of catalysts. The reaction route of DMN oxidation was considered by measuring the concentration of intermediate species. As the intermediate species, 2-formyl-6-naphthoic acid, 2-methyl-6-naphthoic acid and 2-hydroxymethyl-6-methylnaphthalene are found. It was found that the yield of 2,6-naphthalene dicarboxylic acid(NDA) is largely dependent on the Co and Br concentrations. In addition, it was observed that color-b was closely related with Mn concentration in this experimental range. The burning loss of solvent could be reduced by controlling the concentration of Mn and Br. Addition of small amount of Ce and Cu compounds led to increase the NDA yields and decrease the burning amount of solvent.