• Journal of Life Science
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• v.11 no.5
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• pp.483-488
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• 2001

The antimicrobial substance produced by Pseudomonas aeruginosa KLP-2 strain was purified and identified. The substance was identified as a pyocyanine by the fast atom bombardment mass(FAB-MS). In physic-chemical properties, the pyocyanine was dark blue needles, and was soluble in various organic solvents such as chlorogorm, methanol, ethanol and ethyl acetae. The pyocyanine possessed a ultraviolet absorbance spectrum in methanol, 0.1 M HCl, and chlorogorm. The maximum absorption peak of the pyocyanine showed at 318 mm in methanol. The molecular formula of the pyocyanine was determined to the $C_{13}$ H$_{10}$ N$_{2}$O and protonate molecular ion species (M+H)$^{+}$ was observed at m/z 211 by FAB-MS. The pyocyanine showed antimicrobial against Bacillus cereus, Bacillus subtilis, Micrococcus luteus, Rodococcus equi, Staphylococcus aureus, Streptococcus faecalis, E. col, Legionella pneumophila, Shigella flexneri Shigella boydii, shgella sonnei, NAG Vibrio cholerae, Vibrio parahaemolyticus, Vibro vulnificus, Yersinia enterocolitica, and Saccharomyces cerevisiae. However, Salmonella spp. Shigela dysenteriae, 3 strains of Pseudomonas aeruginosa, Klebsiela pneumoniae, and Aspergillus niger were resistant to the pyocyanine. The pyocyanine showed the highest antimicrobial activity aganist Legionella pneumophila based on the size of inhibition zone by the disk contained 0.5 $\mu\textrm{g}$ of the pyocyanine.e.

• Polymer(Korea)
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• v.30 no.2
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• pp.140-145
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• 2006

The mort commonly available substrate material is glass in the display fibrication process. However, glass is not desirable due to its heaviness and fragility. Recently, plastics such polysulfone (PSF), polyethesulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET) and cyclic olefin polymers (COP) have been investigated to replace glass as a substrate material for display fibrication. Plastic substrates are advantageous in that they are lightweight, huh impart resistance, flexibility, and ability for roll to roll manufacturing process. But many plastics have poor chemical resistance in organic solvent. The chemica resistance is also lequired because they are exposed to solvents for various chemical treatments din the manufacturing process. So, we have an interest in the chemical modification of PSF to improve chemical resistance. We introduced crosslinkable imide moieties using chloromethylation method for the modification of PSF which could be overcome above shortcomings for display substrate based on plastic film. We prepared the cross-linked polysulfone films which were represented chemical resistance in HeOH, THF, DMSO and NMP. The thermal properties were measured by TGA, DSC and TMA. As the results, we have confirmed to enhance of the thermal property. They had low coefficient of thermal expansion (CTE) which decreased to 15% and had increased $T_g\;from\;180^{\circ}C\;to\;252^{\circ}C$. Cross-linked polysulfone films with imide side-chain had good optical properties and chemical resistance so that they could be used as flexible display substrate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.

• Polymer(Korea)
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• v.32 no.1
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• pp.13-18
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• 2008

For the evaluation of brominated flame retardants included in polymeric electronic devices, we investigated the extraction methods and solvent systems for four different types of polymers of PC (polycarbonate), PP (polyropylene), PET (poly(ethylene terephthalate)) and PBT (poly(butylene terephthalate)) using different solvent systems of hexane/acetone, THF, toluene, and THF/toluene. In order to compare the extraction efficiency of different methods and solvent systems, the deca-BDE (decabromo diphenyl ether) flame retardant was included in PC, PP, PET and PBT systems and subsequently extracted by soxhlet, ultrasonic, accelerated solvent, microwave and supercritical fluid extraction methods. The amount of the extracted flame retardant was monitored to evaluate the extraction efficiency. The ultrasonic extraction method was found not to be acceptable as an extraction method for the polymer systems mainly due to a low salvation efficiency of the organic solvents. Soxhlet, accelerated solvent and microwave extraction methods exhibited over 80% of extraction efficiency for toluene. The supercritical fluid extraction method, which has been used as an extraction method for flame retardants in polymers, showed the extraction efficiencies of ca. 100% for PC and PP in the optimal extraction conditions of $60^{\circ}C$ and 120 bar.

• Polymer(Korea)
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• v.33 no.3
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• pp.207-212
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• 2009

The precursor polyimide of the photoreactive polyimides(PI-SP6 and PI-SP12) was prepared from a derivative of 2, 2, 2-trifluoroethane dianhydride and 3,3'-dihydroxy-4,4'-diaminobiphenyl. PI-SP6 and PI-SP12 were then prepared by the polymer reactions of the precursor polyimide with photoreactive 2-styrylpyridine alkylene (hexylene and dodecylene) derivatives, respectively. The photoreactive polymers were soluble in organic solvents. The polymers showed the initial decomposition temperatures around $350^{\circ}C$. The glass transition temperatures of PI-SP6 and PI-SP12 were found to be $130^{\circ}C$ and $85^{\circ}C$, respectively. This result means that the latter polymer is more flexible than the former polymer. Their transmittance in the film state was 90% at $250^{\circ}C$, which indicates that the photosensitive polyimides with thermal stability have high optical transparency even at the high temperature. The respective dichroic ratios of PI-SP6 and PI-SP12 were found to be 0.01 and 0.03 at an exposure energy of $1.5\;J/cm^2$. This result suggests that the latter polymer with larger flexibility compared to the former polymer is more effective for the photoalignment.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.567-572
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• 1994

Diglyceride was prepared by reaction of hydrogenated beef tallow and glycerol (GL) in the presence of a Pseudomonas lipase. Both substrates were mixed at the ratio of GL/Triglyceride of 0.5 which is the stoichiometric molar ratio for the complete conversion of triglyceride (TG) to diglyceride (DG). DG can be obtained by solid phase-glycerolysis of hydrogenated beef tallow without use of organic solvents or emulsifiers by careful control of reaction temperature. Optimized reaction temperature condition was as follows: An initial incubation at$60^{\circ}C$ for 2h followed by the first temperature shift down to $55^{\circ}C$ for 4h, and then the second shift down to $50^{\circ}C$ for up to 3 days. There was a large decrease in the content of TG during the first $60^{\circ}C$ incubation for 2h. Even a prolonged incubation at $60^{\circ}C$ could not make a change of the composition of the reaction mixture at liquid state. By controlling the temperature lower than $60^{\circ}C$, reaction mixtures were solidified. The reaction temperature at $50^{\circ}C$ below the melting temperature of hydrogenaed beef tallow gave an 71% optimum yield of DG after 72h enzymatic glycerolysis and about 73% of total DG was 1,3-DG.

• Korean Journal of Food Science and Technology
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• v.26 no.4
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• pp.464-470
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• 1994

The biological activities of Humulus japonicus were extracted by water and methanol. Methanol was better solvent than water in the extraction for antimicrobial activities against six different species of bacteria and two yeasts. The methanol extract was systematically fractionated with various organic solvents which have different polarities. From the result of antimicrobial activities against six species of bacteria and two species of yeasts, methanol extract was superior to water extract. The methanol extract of Humulus japonicus showed antimicrobial activity against the all species of microorganisms tested except Escherichia coli . The butanol fraction of methanol extract showed antimicrobial effect on the all species tested. The minimal inhibition concentration(MIC) of the butanol fraction on the growth of microorganisms was ranged between $0.1{\sim}0.4%$. The water extract of Humulus japonicus did not show inhibition of the activity of trypsin but methanol extract showed inhibitory activity. The chloroform fraction of methanol extract showed comparatively higher trypsin inhibitory activity than other fractions. The concentration of 50% inhibition$(IC_{50})$ by chloroform fraction was 1.0 mg/ml. Enzyme-inhibitor complex formation was above 90% of the while for 20 min. It was revealed that methanol extract of Humulus japonicus inhibited peroxide production of lard and soybean oil as substrate by antioxidative test. The chloroform fraction of methanol extract had the highest activity. When 0.2% of chloroform fraction was added, induction period of soybean oil and lard were extended 15, 9 days, respectively.

• Korean Journal of Food Science and Technology
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• v.24 no.5
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• pp.504-510
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• 1992

Several single or mixed water-miscible organic solvent systems were investigated to develop the most effective solvent system for enzymatic synthesis of N-benzoylaspartame(BzAPM). The BzAPM was prepared by immobilized thermolysin with using N-benzoyl-L-aspartic acid(Bz-Asp) and L-phenylalanine methyl ester(PheOMe). The solubilities of BzAPM and L-phenylalanine were highest in 4.5% methanol(1.89 and 1.79%, respectively) among the solvents system investigated while a mixed solvent system of 25% dimethyl sulfoxide(DMSO) and 20% polyethylene glycol(PEG) 200 showed relatively high values. The synthetic activity of BzAPM as well as initial reaction rate were found to be high in 45% methanol, 45% DMSO and a mixed solvent of 25% DMSO and 20% PEM 200. The imobilized thermolysin was most stable in 25% DMSO and 20% PEG 200 during storage at $40^{\circ}C$ for 42 days. PheOMe in the same solvent system was also found fairly stable against non-enzymatic decomposition at $40^{\circ}C$. Based on the synthetic efficiency and stability, the solvent system containing 25% DMSO and 20% PEG 200 was selected to be appropriate for the enzymatic synthesis of BzAPM.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.6
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• pp.693-700
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• 1992

As an approach to study a new natural antioxidant for edible fats and oils, antioxidative fractions from acorn powder were characterized. The oxidative stabilities of soybean, palm, beef tallow, and lard oil containing the acorn active fraction extracted with various organic solvents were studied by determining the peroxide value during the storage at $60^{\circ}C.$ And this effective antioxidative components were isolated and identified by thin layer chromatography and high performance liquid chromatography. The proximate compositions of acorn powder were water 11.9~12.0%, protein 7.1~7.4%, starch 65.5~69.4%, fat 2.1~2.6%, fiber 2.1~3.6%, ash 2.4~2.6%, and total tannin 4.6~6.8%, respectively. The final yield of fraction extracted by sequential order of acetone : $H_2O$(1 : 1) and ethylacetate was 2.8~3.1%. Gallic acid, digallic acid and gallotannin were contained this final fraction. The main antioxidative activity was speculated due to the presence of gallic acid in acorn powder extract. The antioxidative activity was more effective in fat water emulsion than just fat system. Antioxidative activities measured by peroxide value were quite high in beef tallow and soybean emulsion, but low in lard and palm oil emulsion in the concentration of 200ppm acorn extract. Therefore, the addition of 200ppm acorn extract was suggested to expect effective antioxidation concentration in the reaction system.

• Microbiology and Biotechnology Letters
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• v.3 no.2
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• pp.63-68
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• 1975

A biological active substance was isolated from the cultured medium of Streptomyces sp. and its biochemical characteristics were investigated. Isolation process of the substance was as follows; the pH of filterate of the cultured medium was adjusted to 3.0 with N-hydrochloric acid and saturated with sodium chloride, then chloroform was added to this filterate in one fifth portions and stirred vigorously. After extracting the active substance with chloroform in 3 stages, the chloroform layer combined and evaporatea after dehydrating with sodium sulfate. The substance was found to be to be toxic to various fresh water fishes; the lethal dose for an average size Pseudorasbora parva T. et. S. was 50ug per ml. In the acidic condition, the toxicity of the substance remained fora long time, while in the alkaline state, the toxicity was decreased very fast. This substance was found to be stable to organic solvents, but labile to heat treatment. The maximal revival time of Pseudorasbora parva T. et. S. was about 20 minutes in 25 ug/ml of the substance solution.