• Polymer(Korea)
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• v.25 no.1
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• pp.71-77
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• 2001

Unsaturated polyester(UP) resin is one of the major thermosetting resins. It is very useful as the matrix resin of the composite material because of its low viscosity. The polymer resin, however, has several drawbacks; The volume shrinkage occurs during the crosslinking reaction of the UP resin with styrene monomer and the resulting polymer is weak to the alkali and also brittle. The mechanical properties of UP resin can be improved by blending various materials. In this study, polyurethane(PU) was used as a modifier in order to enhance the toughness of the UP resin. The goal of the research is to study the effect of the polyol molecular weight as a PU soft segment and the PU contents on the toughness of PU-modified UP resins. UP/PU polymer network may occur through the reaction between isocyanate group in the methyldiisocyanate(MDI) and hydroxyl group in the UP molecules. The maximum toughness value was shown at 2 wt% of the PU content. This effect results from the incorporation of the PU segment into the UP resin.

• Polymer(Korea)
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• v.24 no.6
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• pp.737-743
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• 2000

Polyquinonediimines (PQDI) which have stable structure on heat and contains mono-azobenzene in the side chain were synthesized by means of condensation polymerization under TiCl$_4$. The synthesized monomers and polymers were identified by FT-IR, $^1$H-NMR, and elementary analysis. Especially, PQDI was comfirmed by the double-bonding peak of >C=N appeared near 1625 $cm^{-1}$ / by means of FT-IR spectrum. PQDI containing mono-azobenzene group in both side chains wat not soluble in non-polar solvents at all but partially soluble in the polar solvents having small dielectric constant, and dissolved in the strong acid such as sulfuric acid and $CH_3$SO$_3$H. Molecular weight distribution of PQDI measured by GPC showed 1.74. It was confirmed through X-ray diffraction analysis that the polymer was partially crystalline at the low angle region, but amorphous after heat treatment at 1$25^{\circ}C$. The glass transition temperature (T$_{g}$ ) of synthesized polymer was measured as 1$25^{\circ}C$ by differential scanning calorimetry. The SHG value for $\chi$$^{(2)}$ after poling at 1$25^{\circ}C$ was 8.6 pm/V (λ=1.542 ${\mu}{\textrm}{m}$). The SHG value slowly decreased with time from the start but appeared temporal stability after 100 hours.

• Korean Journal of Microbiology
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• v.30 no.4
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• pp.291-298
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• 1992

Srrepromycec. corlirolar produces at least 4 catalase activity bands with different electrophoretic mobilities on polyacrylamide gel which vary during development. Spores and mycelia at stationary phase produced all the activity bands(Cat1. 760 kr); Cat3-I, 170 kD: Cat3-2, 140 kD: Cat3-3. 130 kD; Cat4, 70 kD) except for Cat2 (300 kD). Mycelia at mid-logarithmic phase produced only Cat2 and Cat3-2 bands, and mycelia at late-logarithmic phase produced bands except Catl and Cat\ulcorner. Catalase-deficient mutants were screened in S. coelicalur by H201 bubbling test following NTG mutagenesis. Wc tested sevcral non-bubbling or slow-bubbling mutants for their catalase activities. The overall activities in cell extracts decreased more than 5 fold. Activity bands in native gel selectively decreased in intensity or disappeared. In all the non-bubbling mutants testcd, Cat3-2 band decreased significantly or disappeared. suggesting that Cat3-2 is the major catalase. The selective disappearance of bands in mutants suggest that each band is governed by different genes. We purified catalase activity from -:ell extracts obtained at late-logarithmic phase. Following chromatographies on Sepharose CL-4B. DEAE Sepharose CL-6B. Phcnyl Sepharose CL-4B. and hydroxylapatite columns. only the Cat3-2 activity was obtained. The native form of Cat3-2 has molecular weight of approximately 140 kD, judged by gel electrophoresis. Thc electrophoretic mobility on SDS-polyactylamide gel suggests that this enzyme contains 2 identical subunits of 67 kD.

• Korean Journal of Microbiology
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• v.48 no.4
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• pp.293-297
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• 2012

Of the 169 strains of microorganisms stored in Polar and Alpine Microbial Collection of Korea Polar Research Institute, 27 strains were selected for their chitinase activity on ZoBell plates supplemented with 0.4% colloidal chitin. Among them, PAMC 21693 strain have shown the highest chitinolytic enzyme activity toward pNP-$(GlcNAc)_1$ at low temperature and the highest growth rate at $4^{\circ}C$. We cloned a full-length chitinase gene of 2,857 bp which contains an open reading frame of 2,169 bp encoding 872-amino acid polypeptide. Recombinant chitinase protein was expressed in E. coli and its molecular weight was confirmed 96 kDa. In this paper, we suggest the potential use of cold-active chitinase from polar microorganisms in the field of biotechnology.

• Korean Journal of Microbiology
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• v.45 no.1
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• pp.32-40
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• 2009

To understand contribution of thermophilic microorganisms in decomposition of litter deposits on shore of lakes, we surveyed a lakeshore litter deposit for bacteria growing at $60^{\circ}C$. Ten thermophilic isolates were selected for in-depth characterization, based on their high capacity to degrade high molecular weight organic compounds. Based on phylogenetic analysis on their 16S rRNA gene sequences, all isolates were identified as Geobacillus. The optimal growth temperature and pH of the strains ranged $55{\sim}60^{\circ}C$ and 6.0${\sim}$8.0, respectively. Salinity was inhibitory to the growth of the isolates, showing marked decrease of growth rates at 3% salinity. Based on activities of hydrolytic enzymes and profiles of carbohydrate utilization (determined by API 50 CHB kit), three G. stearothermophilus strains showed patterns clearly distinctive from other isolates. Two G. kaustophilus strains also demonstrated distinctiveness in their metabolic pattern and ecological parameters. However, ecological and metabolic profiles of the other five isolates were more variable and showed some degree of digression from their phylogenetic classification. Therefore, it could be concluded that endospore-forming thermophilic bacteria in lakeshore litter deposits contribute to degradation of organic materials with diverse ecological niches while having successions similar to microbial flora in compost. We propose that the thermophilic isolates and/or their thermo-tolerant enzymes can be applied to industrial processes as appropriate mixtures.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.437-442
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• 2016

A new route for PBT (Poly butylene terephthalate) production from recycled PET (Poly ethylene terephthalate) has been explored. The route consists of glycolysis of PET (Poly ethylene terephthalate) wastes using 1,4-butandiol into BHBT oligomers and polycondensation of the oligomers into PBT oligomer. This process uses post-consumer or post-industrial recycled PET and converts it into high-end PBT type engineering thermoplastic via a chemical recycling process. Zink acetate was used as a catalyst for both glycolysis and polycondensation. Two types of reactor for the glycolysis, batch and semi-batch reactor, were investigated and their performances were compared. Semi-batch reactor removes ethylene glycol (EG) and THF (tetrahydrofuran) during the reaction. Amounts of EG and THF generated during the glycolysis reaction were measured and used as criteria for the reactor performance. Performance of semi-batch reactor was shown to be better than that of batch reactor. Optimum reaction condition for the semi-batch reactor was BD/PET ratio of 4, and reaction temperature of $220^{\circ}C$, giving high EG yield (max 91%) and low production of THF. In addition, it was confirmed that the molecular weight of PBT oligomer increases in accordance with the progress of the polycondensation reaction.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.2
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• pp.231-237
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• 2006

The extracellular enzyme alginase produced by Bacillus licheniformis AL-577 was purified by ion chromatography on CM-Cellulose column, DEAE-Sepharose column, and followed by gel filtration on Sephadx G-100 column. The optimum pH and temperature for the activity of the purified enzyme were 6.0 and $35^{\circ}C$, respectively. The enzyme was stable at the pH range of $6.0\~9.0$ and at $20^{\circ}C$. The molecular weight of the enzyme was estimated to be about 25,500 daltons by SDS-polyacrylamide gel electrophoresis. NaCl was required for high activity of the enzyme. The enzyme was inhibited by $Ba^{2+},\;Co^{2+},\;Cu^{2+},\;Fe^{2+},\;Mg^{2+},\;Zn^{2+},\;NH_4^+$, EDTA, L-cysteine, and 2-mercaptoethanol, while stimulated by DTT, O-phenanthroline, $K^+$ and $Li^+$. This enzyme was proposed to be an alginase specifically degrading alginic acid.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.4
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• pp.635-641
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• 2000

In order to utilize the protein source from a fish proessing by-product, cod was hydrolyzed with various enzymes such as tuna pyloric caeca crude enzyme (TPCCE), a-chymotrypsin, trypsin, papain and pronase E. The TPCCE hydrolysate acquired the highest sensory properties on taste, odor and color. The resultant cod rfame protein hydrolysate (CFPH) which was hydrolyzed with TPCCE, was separated through a series of ultrafiltration membranes with molecular weight cut-off (MWCO) of 30, 10, 5 and 1 kDa, and four types of permeates in cluding 30 K (permeate from 30 kDa membrane), 10 K (permeate from 10 kDa membrane), 5 K (permeate from 5 kDa membrane) and 1 K (permeate from 1 kDa membrane) were obtained. The natural sauces were prepared with 30 K, 10 K, 5 K and 1 K hydrolysate, and the sauce prepared with 1 K hydrolysate was the best score in sensory evaluations. In addition the mixed sauce prepared with 1 K hydrolysate and commercial soy sauce was similar to commercial sauce in sensory properties. These results suggest that the mixed sauce would be utilized as the substitute of acid-hydrolysis sauce.

• Journal of Conservation Science
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• v.27 no.4
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• pp.345-356
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• 2011

To remove metal stains of the ceramics, chemical cleaning is essential case by case. This study investigated the removal characteristics of iron stains by oxalic acid and citric acid including their application methods of soaking and poultice. The soaking method in cleaning agents showed removal process by color difference and released iron contents from iron stains on ceramics. Iron stains were removed successfully from ceramics, which soaked in oxalic acid for 60 hours. However, it is recommendable to soak in 0.25M oxalic acid for one to three hours because most iron stains were disappeared in 3 hours soaking. Citric acid is less effective than oxalic acid in removing iron stains because of heavy molecular weight and low acidity. Poultices (bentonite, sepiolite, activated carbon fiber and celite) with oxalic acid were applied on contaminated ceramics. After ten hours, iron stains on ceramics were removed successfully by poultice. Among them, bentonite and sepiolite have better application. Therefore, sepiolite with 0.25M oxalic acid was applied on the iron stains of whiteware and celadon from Ma Island, and then stains were removed. However, it is judged that the application methods can be varied according to the form and depth of contaminant. In addition, the residues of poultice on the ceramics will be considered for preventing contamination.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.68-74
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• 1999

The optimum conditions for selective .elimination of salt from tuna boiled extract (TBE) by electrodialysis were determined. The desalination conditions of TBE were determined at various pH's, concentrations and volumes of TBE. The ion-exchange membrane with a molecular weight cut off 100Da was used for desalting of TBE. The desalination times on $1\%$ and $10\%$ of TBE concentrations were 40 min and 240 min, respectively. The electrodialysis process could removed above $95\%$ of the initial salt content in $1\%$ and $10\%$ of TBE concentrations. The desalination of TBE at pH 4.0 was $14\%$ higher than that at pH 9.0 The amount of water transferred by the electrodialysis was determined. The electrodialysis process could remove above $90\%$ of the initial salt content in $5\%$ TBE for 80 min. The initial volume and the permeate did not have significant effects on desalination time and ratio. The key parameters for the desalination of TBE were pH and concentration of TBA.