• Korean Journal of Microbiology
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• v.37 no.1
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• pp.92-99
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• 2001

High-cell-density cultivation of Ralstonia eutopha KHB 8862 by fed-batch fermentation in a 200 l pilot plant was carried out for the mass production of poly(3-hydroxybutyrate) (PHB). After 80 h of cultivation, the dry cell weight (DCW), PHB concentration, and PHB yield from fructose syrup reached 168 g/l, 74%DCW, and 0.27 (w/w), respectively, resulting in a productivity of 1.6 g of PHB/L/h. Based on these results, the PHB production cost from bacterial fermentation was analyzed and economic evaluation was performed. In the case of new investment being implemented or not, the production cost of PHB was US$ 3.15/kg and US$ 2.41/kg, respectively. PHB productivity and PHB yield on a carbon substrate were both important factors to be optimized. The increase of PHB yield on a carbon sources significantly decreased the PHB production cost but the increase in productivity had a relatively slight effect on the decrease in PHB production cost because the cost of carbon sources (37%) for PHB was larger in proportion to total cost than the depreciation cost (17%). These results suggest that the increased PHB yield from carbon sources and the development of new cheaper substrates would be more effective in decreasing PHB production cost than the increase in productivity. It was demonstrated that PHB is not in competition with consumable plastics such as PET in present market. Therefore, it is essential to lower production cost to be used as a bulk product and desirable to develop new application fields for PHB such as biomedical and cosmeceuticals.

• Journal of Applied Biological Chemistry
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• v.60 no.4
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• pp.351-355
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• 2017

Tolaasin, peptide toxin produced by Pseudomonas tolaasii, causes a brown blotch disease on the cultivated mushrooms. Tolaasin peptides form membrane pores and disrupt cellular membrane structure. Molecular actions of tolaasin consist of the aggregation of peptide molecules, binding to the cell membrane, and formation of membrane pores. Therefore, the inhibitions of any of these actions are able to suppress the blotch disease. We have isolated and identified several tolaasin inhibitors (named tolaasin inhibitory factors, TIF) from food additives. TIFs were able to suppress the blotch-formation by the pathogen inoculated to the mushrooms. In this study, TIFs were incubated under various conditions and their activities for the inhibition of tolaasin-induced hemolytic activity were investigated. Since TIFs are unsaturated carbon compounds, they were sensitive to the air exposure and light irradiation. In the anaerobic conditions, TIFs were stable and their activities were decreased by 10% for three months. However, near 90% of TIF activity was suppressed by two weeks in the presence of air and sun light. Temperature did not show any significant effects on the activity of TIF, since storages at 5, 25, $45^{\circ}C$ did not show any difference. Therefore, for the stable storage of TIF compounds, container should be designed to be dark and air-tight.

• Applied Biological Chemistry
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• v.45 no.2
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• pp.53-58
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• 2002

Quinacrine, a pH-sensitive fluorescence probe, which exists either as an unprotonated fluorescence form or a protonated noufluorescence form, can be used to measure the proton transport activity of $H^+-ATPase$. Quinacrine was used to determine the optimal conditions for measuring the activity of microsomal $H^+-ATPase$ prepared from the roots of tomato plants. The amount of quinacrine fluorescence quenching obtained at $0.43{\mu}g/{\mu}l$ of microsomal protein concentration was 25-26%, which shows that the enzyme activity of 100 nmol/min decreases 10% of quinacrine fluorescence. Maximal fluorescence quenching was obtained at pH 7.0-7.2 and 2 mM $Mg^{2+}$ Because the activity of microsomal $H^+-ATPase$ is also maximal at these conditions, the quinacrine fluorescence well represents the activity of $H^+-ATPase$. Vanadate and $NO_3-$, specific inhibitors of plasma and vacuolar $H^+-ATPases$, respectively, were successfully applied to inhibit the quinacrine fluorescence quenching mediated by the corresponding $H^+-ATPases$. These results imply that quinacrine is a useful tool for measuring the proton transport activities of microsomes obtained from the root tissue of tomato plants.

• Korean Journal of Environmental Agriculture
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• v.21 no.2
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• pp.102-108
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• 2002

In order to investigate the mechanism of growth inhibition by salt stress, lettuces were grown hydroponically in three different nutrient solutions, normal and 30 mM or 50 mM $KNO_3$-added nutrient solutions, and the electrical conductivities of these solutions were 1.0, 4.5, and 6.5 dS/m, respectively. The activities of plasma and vacuolar $H^+$-ATPases in the root tissue of lettuce were measured by specific inhibitors, 100 ${\mu}M$ vanadate and 50 mM $NO_3^-$, respectively. Microsomal ATPase activity of lettuce grown in the normal nutrient solution was $356\pm1.5$ nmol/min/mg protein. When lettuces were grown in 30 mM and 50 mM $KNO_3$-added nutrient solutions, total activities of microsomal ATPases were increased by 1.6 and 1.9 times, respectively, and the increases were mainly mediated by vacuolar $H^+$-ATPase. These results show that lettuces adapt themselves to salt-stressed condition by increasing the activities of $H^+$-ATPases. Effects of various heavy metal ions were investigated on the microsomal ATPases and various metal ions at 100 $\mu M$ inhibited the activities by 10$\sim$25%. $Cu^{2+}$ showed the highest inhibitory effect on the vacuolar $H^+$-ATPase. These results suggest that lettuce increases the activities of root ATPases, specially that of vacuolar $H^+$-ATPase, in salt-stressed growth conditions and $Cu^{2+}$ could be a useful tool to control the activity of vacuolar $H^+$-ATPase.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.28-33
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• 2001

Lettuces were grown hydroponically in three different nutrient solutions, normal and 30 or 50 mM $KNO_3-added$ nutrient solutions, and the electrical conductivities of the nutrient solutions were 1.0, 4.5, and 6.5 dS/m, respectively. Lettuces grown in the $KNO_3-added$ nutrient solutions showed a decrease in the germination ratio and the lower indices of growth, such as plant height, stem diameter, leaf length, and leaf width. Microsomes were prepared from the roots of lettuce and characteristics of microsomal ATPases were investigated. The activities of microsomal ATPases grown in the 30 mM and 50 mM $KNO_3-added$ nutrient solutions were higher than that grown in the normal nutrient solution. The highest activities of microsomal ATPases were observed at pH 7.0 in all culture conditions. The activities of microsomal ATPases were increased in a reaction buffer solution containing high concentration of $K^+$, whereas they were decreased in a reaction buffer containing $Na^+$. The stimulating effect of $K^+$ in the reaction buffer was greater on the microsomal ATPases of lettuces grown in the $KNO_3-added$ nutrient solutions than that grown in the normal nutrient solution. These results imply that the activities of microsomal ATPases in the root tissue are increased as increasing the $KNO_3$ concentration in the hydroponical nutrient solution.

• Journal of Life Science
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• v.15 no.3 s.70
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• pp.434-438
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• 2005

In the previous study, we isolated a myulchikinase (MK), which has fibrinolytic activity and cytotoxicity to the tumor cell line, from myl- chi-jeot-gal. In this study, the effect of NaCl concentration, metallic ions, pH, temperature, and plasminogen on the activity of MK was analysed. The MK activity was maintained at least $80\%$ activity up to $30\%$ NaCl, which indicates that the enzyme may be halotolerant. The optimal pH and temperature were 8 and $40^{\circ}C$, respectively. The fibrinolytic activity of MK was completely inhibited with 0.5 mM $Hg^{2+}$ and inhibited to $50^{\circ}C$ with 1 mM $Cu^{2+}\;and\;Zn^{2+}$. The MK showed strong activity in plasminogen- rich fibrin plate but not in plasminogen-free fibrin plate. The result indicates that the MK may be a plasminogen activator type fibrinolytic enzyme.

• Journal of the Korean Society for Library and Information Science
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• v.41 no.4
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• pp.93-111
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• 2007

The Internet is now an integral part of the everyday lives of a majority of people. Web users are becoming increasingly skeptical of the information and services offered online. They are demanding web sites that offer credible information. This study focused on what features of web sites affect the perception of web credibility. For this purpose, I took the responses from 648 people and extracted 49 factors that affect web credibility. I placed the individual factors - the specific questions asked in the survey - into one of four categories expertise. trustworthiness, ads and other and calculated the means for each of the 49 factors. As a result, 29 out of 49 factors increase the Perceptions of credibility and 20 factors decrease the web credibility. Sites with frequently update. the credentials of authors, strict content guides, search capabilities, clear connections to the real world fared good in credibility. Technical problems such as broken links, site sown, or typographical errors were rated the most negative on this scale On the other end of the scale, a domain name that ends in' .org' or' .or.kr' caused little change in perception of credibility.

• Korean Journal of Head & Neck Oncology
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• v.30 no.2
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• pp.62-67
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• 2014

Background and Objectives : To investigate the prognostic factors and effectiveness of radiotherapy for oropharyngeal cancer. Material and Methods : Forty seven patients in oropharyngeal cancer treated with radiotherapy between November 1989 and October 2010. Conventional radiotherapy was performed until July 2007 and conformal radiotherapy was performed since August 2007. Median age of patients was 59. Thirty five patients were males. Nine patients had operation. Patients treated with postoperative radiotherapy were delivered median 60 Gy and patients treated with definitive radiotherapy were delivered median 66 Gy. Median follow-up periods were 51 months. Results : Two year and 5 year overall survival rate was 78.7% and 59.9%. Two year and 5-year locoregional recurrence free survival rate was 82.3% and 72.9%. In subgroup of definitive radiotherapy, at univariate analysis for overall survival, lower N stage(p=0.01), lower stage(p=0.05) and well and moderate differentiation(p=0.001) were statistically significant. At univariate analysis for locoregional recurrence free survival, lower T stage(p=0.02) and better differentiation(p=0.043) were statistically significant. Treatment failure occurred in 12 patients. Locoregional recurrence(8 patients) was main pattern of failure. Conclusion : When definitive radiotherapy compared with postoperative adjuvant radiotherapy, there was no significant difference. Further studies would be needed to compare definitive radiotherapy with postoperative radiotherapy. N stage, stage and differentiation could be the prognostic factors for overall survival and T stage and differentiation could be the prognostic factors for locoregional recurrence free survival in patients treated definitive radiotherapy.

• Development and Reproduction
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• v.3 no.1
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• pp.21-28
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• 1999

In order to examine the effect of $Ca^{2+}$ -chelation on in vitro fertilization of rat zona-free oocyte, the formation of cortical granule envelope (CGE) and the rate of fertilization related to monospermy and polyspermy were determined. The ultrastructural characteristics of oocytes were observed with the scanning electron microscope and BAPTA/AM was used for calcium-chelation. The CGE formed by cortical reaction was observed in zona-free oocyte inseminated in vitro and it was also observed in the calcium chelator (1, 5, 10$\mu$M BAPTA/AM) treated zona-free oocytes inseminated in vitro. The CGE developed according to incubation time. The fertilization rate was decreased in the calcium chelator-treated group (59.8, 38.1, 37.0%) compared to the control group (60.6%) but monospermy rate was increased in the calcium chelator-treated group (45.0, 47.3, 50.9%) compared to control group (37.5%). The above results demonstrate that the CGE is formed during fertilization in rat and the extracellular calcium is used in cortical reaction. Also the results suggest that proper concentration of free calcium in oocyte acts as important factor in fertilization.n.

• Journal of Environmental Impact Assessment
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• v.27 no.3
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• pp.251-266
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• 2018

This study predicted the effect of operation pattern of flood control dam on water quality. Flood control dam temporarily impound floodwaters and then release them under control to the river below the dam preventing the river ecosystem from the extreme flood. The Hydrological Simulation Program Fortran (HSPF) and the Environmental Fluid Dynamics Code (EFDC) were adapted to predict the water quality before and after the dam construction in the proposed reservoir. The non-point pollutant delivery load from the river basin was estimated using the HSPF, and the EFDC was used to predict the water quality using the provided watershed boundary conditions from the HSPF. As a result of water quality simulation, it is predicted that the water quality will be improved due to the decrease of pollution source due to submergence after dam construction and temporary storage during rainfall. There would be no major water quality issues such as the eutrophication in the reservoir since the dam would impound the floodwater for a short time (2~3 days). In the environmental impact assessment stage of a planned dam, there may be some limitations to the exact simulation because the model can not be sufficiently calibrated. However, if the reliability of the model is improved through the acquisition of actual data in the future, it will be possible to examine the influence of the water environment according to various operating conditions in the environmental impact assessment of the new flood control dam.