• Korean Journal of Food Science and Technology
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• v.38 no.4
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• pp.584-588
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• 2006

This study was carried out to optimize the conditions for the extraction of antioxidative materials from licorice root, Glycyrrhiz glabra. Chipped licorice roots were extracted with several solvents and their antioxidative activities were tested to determine the optimal extraction solvent. Among the solvents tested, 95% ethanol gave the highest free radical scavenging activity, and was therefore chosen as the optimal extracting solvent. The optimum extraction temperature and time were $20^{\circ}C$ and 12 hr, respectively. Next, the free radical scavenging activity of the ethanol extract was compared with that of other known antioxidants such as ${\alpha}-tocopherol$, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). Ethanol extract of licorice root had greater antioxidative activity than ${\alpha}-tocopherol$ and a similar level to that of the two synthetic antioxidants (BHA and BHT). Moreover, the antioxidative activity of the ethanol extract was inhibited neither by heat treatment at $180^{\circ}C$ for 30 min nor by treatment at extreme pH. These findings suggest that ethanol extract of G. glabra may be useful as a natural antioxidant.

• Elastomers and Composites
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• v.47 no.1
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• pp.9-17
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• 2012

Herein, life time prediction based on the deterioration of physical properties of chloroprene rubber (CR)aged by heat and seawater was performed. CR samples were experienced an accelerated test at $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$ for heat aging, and $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ for seawater aging for 20,000 hrs. The change in tensile strength, maximum elongation,hardness was measured. As a result, the decrease in elongation was a major factor causing failure. The life time estimated using an Arrhenius model was 125 years at $23^{\circ}C$ for thermal aging and 9 years at $23^{\circ}C$ for seawater aging. SEM and elemental analysis reveal that cracks were generated and the content of oxygen was increased for CR agined by seawater. FT-IR spectrum shows the new C-O and C = O bonds were generated by the chemical reaction with seawater. Also, the glass transtion temperature was increased and the thermal decomposition was decreased by seawater aging.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.44-49
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• 1996

By using the ${\beta}$-tyrosinase of Citrobacter freundii KCT2006, which was cloned and overexpressed in Escherichia coli, 3,4-dihydroxy phenyl-L-alanine (L-DOPA) was synthesized efficiently from pyrocatechol, sodium pyruvate, and ammonium acetate. Optimal temperature and pH for the reaction were determined to be about 18$^{\circ}C$ and 8.5, respectively. The effects of substrate concentrations were also examined at different concentrations of ammonium acetate, sodium pyruvate, and pyrocatechol. Ammoniumacetate and sodium pyruvate increased the reaction rate until the concentrations reached to 300mM and 50mM, respectively. Although pyrocatechol showed the optimal concentration at 20mM, it was controlled between 20mM and 50mM to avoid the depletion of substrate during the enzymatic synthesis. Meanwhile the synthetic rate was improved about 20% when ethanol was included in the reaction solution. Based on above results, a reaction medium for the productin of L-DOPA was prepared and incubated with 1 unit/ml of ${\beta}$-tyrosinase. Pyrocatechol and sodium pyruvate was added to the reaction solutin intermittently to avoid the substrate depletion during the enzymatic reaction. After 24 hour of reaction, 31.6g/l of L-DOPA was accumulated in the reaction solution as soluble and precipitated ones and the conversion yield was about 85.2%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.645-653
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• 2017

In bone tissue engineering, polycaprolactone (PCL) is one of the most widely used biomaterials in the manufacturing of scaffolds as a synthetic polymer having biodegradability and biocompatibility. The strut width in the fabrication of scaffolds is an important part of tissue regeneration in in-vitro and in-vivo experiments, because it affects not only the pore size but also the porosity. In this study, we used polymer deposition system (PDS) and design of experiments (DOE) to explore the optimal process conditions to achieve a systematic and efficient scaffold manufacturing process, using temperature, pressure, scan velocity, and nozzle tip height as the parameters for the experiments. The aim of this research was to fabricate a 3D PCL scaffold having a uniform strut width of $150{\mu}m$ using DOE; it was proved that the strut width was constant in all the experimental groups by fabricating the PCL scaffolds according to various pore patterns as well as one pore pattern.

• Korean Journal of Environmental Agriculture
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• v.31 no.2
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• pp.170-174
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• 2012

BACKGROUND: Inappropriate discharge of wastewaters and industrial effluents are becoming detrimental to the aquatic environment. The presence of toxic substances on wastewaters can be detected by physicochemical and biological methods. However, physicochemical methods do not give any information about biological toxicity. Therefore, in this study we tried to detect the presence of toxic substance on waters using sulfur-oxidizing bacteria (SOB) as a bioassay. MATERIALS AND RESULTS: The SOB biosensor was first stabilized using synthetic stream water and operated in both continuous and semi-continuous mode. When the SOB biosensor was operated in continuous mode, the effluent electrical conductivity (EC) stabilized at~1.72 dS/m. While in the case of semi-continuous, the EC stabilized at~0.6 dS/m. The SOB system was also operated at different reaction times to ascertain the shortest reaction time for monitoring the toxicity. Finally, the SOB biosensor was fed with nitrite as toxic substance. When 5 mg/L of nitrite was added to the SOB system, the EC decreased immediately. However, the EC recovered after few cycle. CONCLUSION: This study shows that the SOB biosensor can be used as warning system to protect aquatic environment from hazardous materials. Although SOB biosensor can not give specific information about the toxic substances, it can assess whether the water is toxic or not.

• Journal of Life Science
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• v.15 no.3 s.70
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• pp.317-322
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• 2005

The cycloinulooligosaccharide fructanotransferase (CFTase) gene (cft) from Paenibacillus macerans was subcloned into an E. coli-yeast shuttle vector, pYES2.0, resulting in pYGECFTN. The plasmid pYGECFTN (8.6 kb) was introduced into Saccharomyces cerevisiae SEY2102 cells and then the transformants were selected on the synthetic defined media lacking uracil. The cft gene expression in yeast transformant was demonstrated by the analyses cyclofructan (CF) spots on thin-layer chromatogram. The recombinant CFTase was not secreted into the medium and localized in the periplasmic space. The production of CF was observed after 5 min of the enzymatic reaction with inulin. The optimun pH and temperature for CF production were found to be at pH 8.0 and $45^{\circ}C$, respectively. Enzyme activity was stably maintained up to $55^{\circ}C$. The CF was produced from all inulin sources and was most efficiently produced from dahlia tubers and Jerusalem artichokes.

• Journal of Life Science
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• v.17 no.2 s.82
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• pp.241-247
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• 2007

The cycloinulooligosaccharide fructanotransferase (CFTase) gene (cft) from Paenibacillus macerans was subcloned into the surface display vector, pCTcon (GAL1 promoter). The constructed plasmid, pCTECFTN (9.0 kb) was introduced to S. cerevisiae EBY100 cell and then east transformants were selected on the synthetic defined medium lacking uracil and on the inulin containing medium. The surface display of CFTase was confirmed by immunofluorescence microscopy and its enzymatic ability to form cycloinulooligosaccharides(cyclofructans, CFs) from inulin. The total activity of the CFTase was reached about 5.52 unit/1 by cultivation of yeast transformant on YPDG medium. The optimized conditions determined were as follows; pH, 8.0; temperature, $50^{\circ}C$ ; substrate concentration, 5%; inulin source, Jerusalem artichoke. By the reaction with inulin, CFs consisting of cycloinulohexaose (CF6), cycloinuloheptaose (CF7), and cycloinulooctaose (CF8) were produced and CF6 was the major product.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.336-345
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• 2002

In this study, we have screened $Eu^{3+}$- and $Tb^{3+}$-activated candidate phosphors for PDP in the sys-tems of CaO-Gd$_2$O$_3$-Al$_2$O$_3$ by combinatorial chemistry and investigated the synthetic temperature, optimum com-position and luminescent properties about the candidate phosphors. To construct the emission intensity library by VUV PL, we have synthesized 210 different compositional samples using a polymerized-complex method. Good luminescent samples were identified by X-ray diffraction method. $Ca_$\alpha$$G$d_{0.95-$\alpha$-$\beta$}Al_$\beta$O_$\delta$$ : Eu(0.02< $\alpha$+$\beta$ <0.04) phos-phors screened as a red phosphor have good color purity than commercial phosphor. In the candidate phosphors of CaGdAl$_3O_7$ : Tb, Ca$Al_{12}O_{19}$ : Tb, Gd$_4$Al$_2O_9$ : Tb, and Gd$_3Al_5O_{12}$ : Tb CaGdAl$_3O_7$ : Tb, and Ca$Al_{12}O_{19}$ : Tb have shorter decay time than commercial phosphor.

• The Korean Journal of Mycology
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• v.24 no.3 s.78
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• pp.214-222
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• 1996

This study was carried out to obtain the basic data on artificial culture of Phellinus linteus. The optimum condition for the mycelial growth was $25{\sim}30^{\circ}C$ and pH $6.0{\sim}7.0$. The carbon sources such as D-glucose, D-mannose and Dextrose were favorable to mycelial growth. As nitrogen sources, peptone, cassamino acid and glutamic acid appeared to be favorable. The optimum C/N ratio was about 20:1, when 2% of glucose was provided as a carbon source. The better organic acids and vitamin among tested ones were gallic, silicic acids and biotin. The mineral nutrients of $KH_2PO_4,\;FeSO_4{\cdot}7H_2O,\; MgSO_4{\cdot}7H_2O,\;ZnSO_4{\cdot}7H_2O$ were effective and the optimum concentrations were 0.05, 0.001, 0.02 and 0.003%, respectively.

• The Korean Journal of Mycology
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• v.42 no.3
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• pp.213-218
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• 2014

Water extract from spent mushroom substrates (SMS) of Pleurotus eryngii was utilized in decolorization of eight synthetic dyes and wastewater from a textile factory. High laccase activity was detected in the extract of P. eryngii (SMSE). The SMSE showed that decolorization rate was 34~93% after 24 h incubation without any mediator on eight dyes including Rit-blue and Rit-red used in fiber dyeing. Dye decolorization rate more than 90% was observed on bromophenol blue and remazol brilliant blue R (RBBR). Dye in textile wastewater was decolorized at room temperature after three days by addition of P. eryngii SMSE. The results suggest that biological decolorization of dyes using the P. eryngii SMSE can be used as environmental friendly materials.