• The Journal of the Korea Contents Association
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• v.13 no.3
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• pp.352-361
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• 2013

The purpose of this study is to analyse the impact of macroeconomic and non-macroeconomic forces on the management performance of the air transport firms and offer the useful information to the managers. To conduct the regression analysis, eight macroeconomic and non-macroeconomic variables were selected individually as an independent variable. Macroeconomic variables were the return of corporate bond, West Texas Intermediate, the unemployment rate, the money supply, the trade balance, the won to USD exchange rate, the consumer price index and the index of industrial production. And non-macroeconomic variables were Taiwan earthquake, the Asian economic crisis, the 911 terrorist attacks in the US, the Iraq war, Beijing Olympic, the outbreak of a swine flu epidemic, the 1st presidential election and the 2nd presidential election. And ROA was selected as a dependent variable. As the result of analysis, it was found that the changing rates of won to USD exchange rate and consumer price index affected the changing rate of ROA significantly. And also as the result of analysing the impact of two significant macroeconomic variables and eight non-macroeconomic variables on the changing rate of ROA, it was found that the Asian economic crisis and the outbreak of a swine flu epidemic had a negative impact on it. Therefore managers should take note of a change in macroeconomic and non-macroeconomic variables carefully to improve the management performance.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.83-91
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• 2012

Quorum sensing (QS) is a cell-to-cell communication system, which is used by many bacteria to regulate diverse gene expression in response to changes in population density. Bacteria recognize the differences in cell density by sensing the concentration of signal molecules such as N-acyl-homoserine lactones (AHL) and autoinducer-2 (AI-2). In particular, QS plays a key role in biofilm formation, which is a specific bacterial group behavior. Biofilms are dense aggregates of packed microbial communities that grow on surfaces, and are embedded in a self-produced matrix of extracellular polymeric substances (EPS). QS regulates biofilm dispersal as well as the production of EPS. In some bacteria, biofilm formations are regulated by c-di-GMP-mediated signaling as well as QS, thus the two signaling systems are mutually connected. Biofilms are one of the major virulence factors in pathogenic bacteria. In addition, they cause numerous problems in industrial fields, such as the biofouling of pipes, tanks and membrane bioreactors (MBR). Therefore, the interference of QS, referred to as quorum quenching (QQ) has received a great deal of attention. To inhibit biofilm formation, several strategies to disrupt bacterial QS have been reported, and many enzymes which can degrade or modify the signal molecule AHL have been studied. QQ enzymes, such as AHL-lactonase, AHL-acylase, and oxidoreductases may offer great potential for the effective control of biofilm formation and membrane biofouling in the future. This review describes the process of bacterial QS, biofilm formation, and the close relationship between them. Finally, QQ enzymes and their applications for the reduction of biofouling are also discussed.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.234-243
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• 2018

The Antarctic Ocean contains numerous microorganisms that produce novel biocatalysts that can have applications in various industries. We screened various psychrophilic bacterial strains isolated from the Ross Sea and found that a Croceibacter atlanticus strain (Stock No. 40-F12) showed high lipolytic activity on a tributyrin plate. We isolated the corresponding lipase gene (lipCA) by shotgun cloning and expressed the LipCA enzyme in Escherichia coli cells. Homology modeling of LipCA was carried out using the Spain Arreo lake metagenome alpha/beta hydrolase as a template. According to the model, LipCA has an ${\alpha}/{\beta}$ hydrolase fold, Gly-X-Ser-X-Glymotif, and lid sequence, indicating that LipCA is a typical lipase enzyme. Active LipCA enzyme was purified fromthe cell-free extract by ammonium sulfate precipitation and gel filtration chromatography. We determined its enzymatic properties including optimum temperature and pH, stability, substrate specificity, and organic solvent stability. LipCA was immobilized by the cross-linked enzyme aggregate (CLEA) method and its enzymatic properties were compared to those of free LipCA. After cross-linking, temperature, pH, and organic solvent stability increased considerably, whereas substrate specificities did not changed. The LipCA CLEA was recovered by centrifugation and showed approximately 40% activity after 4th recovery. This is the first report of the expression, characterization, and immobilization of a C. atlanticus lipase, and this lipase could have potential industrial application.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.9
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• pp.636-643
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• 2011

Sludge solubilization using sonification has been increasingly used for sludge volume reduction along with enhancing digestion efficiency during anaerobic biogas production. In this study, either electric field or ultrasonification or in combination with were investigated using three types of sludge (return, excess and mixed at G sewage treatment facility) for the most efficient solubilization. As a the closed loop, 200 L of sludge was continuously passing through the solubilization system at an average flow rate of $0.7m^3/h$, which is equivalent to 3.5 times treated per hour for up to 84 times (24 h). Only implying electric field showed no variation for sCOD/tCOD before and after treatment on sludge solubilization regardless of types of sludge. However, employing the ultrasonic or combined system could both increasingly solubilize sludge with regard to the number of passing-through, which more enhanced by the combined. In addition, VSS/TSS was lowered to in the range of 2 and 6% while its particle size, diameter (0.9) and diameter (0.5) were more minimized than that of raw sludge. For return sludge, ultrasonification was more efficiently facilitated for solubilization, whereas electric field-ultrasonification was more preferably applied for excess and mixed sludge. It is concluded that depending on types of sludge, solubilization system must be selectively applied for the most efficient break-up of them.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.1
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• pp.11-19
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• 2015

The production of nuclear fuel cladding tube is expected to increase with the nuclear power plant expansion. Zirconium(Zr) scrap that is generated during manufacturing is also expected to increase. Zr electrorefining experiment was carried out in the fluoride salt of LiF-KF-ZrF₄ using multiple electrode for scale up and improving throughput Zr electrorefiner develop-ment. The Zr reduction peak observed at-0.8 V(vs.Ni). Polarization behavior showed that the amount of applied current increases because of decreasing cell resistance as the number of cathode increases. Experimental results showed the highest recovery rate about 98% at lowest current density of 25.64 mA/cm² using 6 electrodes. XRD and TG analysis result show that pure Zr was recovered 99.92% and ICP analysis shows that lower impurity content than conventional impurity content of the Anode(97.8%). Electrorefining consumes energy about 7.15 kWh/kg less than 39.7% compared to the Kroll process using 6 electrode width of 20 mm and height of 65 mm. Because of increasing cell efficiency and recovery rate, using multiple cathode is determined as an efficient technique for scale up electrorefining Zr scrap.

• Analytical Science and Technology
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• v.27 no.2
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• pp.100-107
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• 2014

Plastic has been widely used in modern artworks' materials due to its merits of process ability and mass production. In the country, value of plastic artifact is increasing but the field of plastic study is limited to industrial purpose. In this study, Identification methods of plastic were performed by SPME-GC/MS and pyrolysis-GC/MS using trace of samples. As a result of identification using SPME-GC/MS, aromatic compounds were identified from polyvinyl chloride. And alkane compounds were identified from polyethylene, and polypropylene. Aromatic compounds were identified from polystyrene, and diethylene glycol appeared in polyurethane based on polyester was identified from polyurethane. As a result of identification using pyrolysis- GC/MS, aliphatic alkenes compounds and phthalate(DEHP) were identified from polyvinyl chloride. Aliphatic alkenes compounds and phthalate(DIBP) were detected from polyethylene. 1-hexene, etc., were detected from polypropylene, aromatic compounds were identified from polystyrene, and methylene diphenyl diisocyanate which is polyurethane basic material was confirmed from polyurethane. This study suggested that non-destructive SPME and pyrolysis-GC/MS are useful to identify compounds particularly polystyrene and polyurethane. These two analytical methods were expected to be applied for identification of unidentified plastic artworks before conservation treatment.

• Journal of the Korean Applied Science and Technology
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• v.37 no.4
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• pp.1041-1051
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• 2020

The technology of microbubbles and nanobubbles originated in Japan and Europe is applicable to various applications and its effects are diverse, attracting attention not only from many researchers but also from industry experts. In particular, nanobubbles have the advantage that they can be applied to products in the form of liquids, such as cosmetics, from the study that they can exist for more than several months in water. In this study, it was carried out the production of nanobubbles using bubble encapsulation technique and the experiment of skin permeability enhancement of active substances in cosmetics using nanobubble techniquethree. Nanobubbles were confirmed to affect the skin permeability increase of active substances, and up to 250% increase in skin permeability compared to non-bubbles-free materials(Caffeic acid, at 8 hour). It is expected that research results and industrial ripple effects can be expected not only in the cosmetic field, but also in fields applicable to the improvement of permeability by nanobubble techniques, such as areas related to drug delivery system.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.414-419
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• 2005

The current study was conducted to investigate the effects of dietary chitosan-alginate-Fe(II) complex (CAFC) supplementation on carcass and meat qualities of pig m. longissimus during chiller ageing. One hundred and twenty-two LYD (Landrace${\times}$Yorkshire${\times}$Duroc) pigs were sampled from an industrial population. Seventy-four pigs (32 gilts and 42 barrows) were administered 3 ml of dietary supplementation of CAFC per day from 25 to 70 days of age, while the remaining 48 pigs (20 gilts and 28 barrows) were fed the same commercial feeding regime without the supplementation. For assessing the dietary effects on pH, objective meat color, cooking loss, water-holding capacity (WHC), thiobarbituric acid reactive substances (TBARS), volatile basic nitrogen (VBN) and fatty acid composition during ageing, 20 barrows (10 of each treatment) were randomly sampled, and aged for 3, 7, 12, 16, 20 and 25 days in a $1^{\circ}C$ chiller. The results showed that CAFC-fed pigs required approximately 10 fewer feeding days than the control group. Furthermore, the treatment resulted in greatly higher carcass grade whereby the grade A was increased by approximately 35% and 7% for gilts and barrows, respectively. The treatment had no significant effect (p>0.05) on pH, meat color and WHC during ageing. On the other hand, the CAFC-fed pigs showed significantly (p<0.05) lower TBARS values from 20 days of storage. In addition, the sum of unsaturated fatty acids for the treated group was significantly (p<0.05) higher than that for the control group after the storage time. This implied that CAFC supplementation could reduce the formation of free radicals in fatty acids (i.e., lipid oxidation). The treatment also significantly (p<0.05) retarded VBN formation during ageing, indicating a significant reduction in protein degradation. However, as there was no difference in pH between the two groups, the result raised a possibility that antibacterial activity of the CAFC alone could cause reduction in the formation of TBARS and VBN. In this regard, although the treatment effectively slowed down the formation of TBARS and TBA during chiller ageing, it was not resolved whether that was associated with the direct effect of the antioxidant function of chitosan and/or alginate, or a consequence of their antibacterial functions.

• Journal of Applied Biological Chemistry
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• v.54 no.4
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• pp.252-257
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• 2011

To remove excess nitrate from the agricultural environments, Enterobacter amnigenus GG0461 has been isolated as a bacterial strain having high capability of nitrate uptake activity. This strain was able to remove nitrate more than 3,000 ppm (50 mM) in the Pseudomonas agar F (PAF) medium. Therefore, it could be a candidate strain for a nitrate scavenger in the various contaminated environments, such as agricultural soils, livestock sewage, and industrial wastewater. In order to develop medium for the large-scale production of the strain GG0461, each component of PAF medium was replaced with the corresponding commercial product and the optimal conditions for bacterial growth and nitrate uptake activity were measured. Glycerol was replaced with the commercially available product and the nitrogen source was substituted with commercial tryptone, yeast extract, soybean meal, and fermented fish extract. Bacterial growth and nitrate uptake activity were maximal in the media containing 2% tryptone, followed by yeast extract, soybean meal, and fermented fish extract. The pH of the growth medium containing 2% tryptone was decreased by the bacterial nitrate uptake, suggesting that the nitrate uptake is mediated by a nitrate/proton antiporter. This result shows that the medium containing commercial tryptone was good enough for the physiological activity of the strain GG0461. Each component of PAF medium was successfully replaced with the corresponding commercial product except peptone. In conclusion, the composition of medium for the cultivation of the strain GG0461 was determined as 2% tryptone, 1% glycerol, plus required salts according to the composition of PAF medium.

• Journal of Microbiology and Biotechnology
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• v.26 no.4
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• pp.730-738
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• 2016

est19 is a gene from Bacillus sp. K91 that encodes a new esterase. A comparison of the amino acid sequence showed that Est19 has typical Ser-Gly-Asn-His (SGNH) family motifs and could be grouped into the SGNH hydrolase family. The Est19 protein was functionally cloned, and expressed and purified from Escherichia coli BL21(DE3). The enzyme activity was optimal at 60℃ and pH 9.0, and displayed esterase activity towards esters with short-chain acyl esters (C₂-C₆). A structural model of Est19 was constructed using phospholipase A1 from Streptomyces albidoflavus NA297 as a template. The structure showed an α/β-hydrolase fold and indicated the presence of the typical catalytic triad Ser49-Asp227-His230, which were further investigated by site-directed mutagenesis. To the best of our knowledge, Est19 is a new member of the SGNH hydrolase family identified from thermophiles, which may be applicable in the industrial production of semisynthetic β-lactam antibiotics after modification.