• KSBB Journal
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• v.7 no.4
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• pp.258-264
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• 1992

The rheological characteristics of the ethanol fermentation broth were pseudoplastic when the yeast concentration was above 150g/L. From the viewpoint of rheological properties, the cell concentration below 150g/L was recommended for ethanol fermentation. Since the cell floc was formed at the cell concentration of 100 g/L, yeast cells were not much plugged in the pores of the membrane. The cell concentration above 100g/L was desirable when considering the permeability of the membrane. Since ethanol productivity was the highest when the cell concentration was 130 g/L in cell recycled ethanol fermentation. The optimal dilution rate was determined at 1.3 h-1 at constant cell mass of 130g/L. At this dilution rate, the ethanol productivity and glucose conversion ratio ware 80 g/L$\cdot$h and 0.94, respectively.

• Membrane Journal
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• v.19 no.1
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• pp.19-24
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• 2009

Sol-gel process is relatively simple, easy to use, cheap to install, and results in thin coating layers with superior physical and gas barrier properties. Films coated by the sol-gel process can be used as insulating films or packaging films for foods, chemicals, drugs, and beverages, etc. In this study, alumina sol was synthesized from aluminum isopropoxide and silane coupling agent was added to make coating solutions. In addition, biaxially oriented polypropylene (BOPP) was coated using several alumina sol solutions and their oxygen permeabilities were measured. The experimental results indicate that in the best case, the oxygen permeability of coated film was reduced by 85% compared to that of pure BOPP.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.421-424
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• 2006

Nafion/Pt/Polypyrrole composite membranes were fabricated by chemical in-situ polymerization of pyrrole monomers with Pt precursors in Nafion matrix for DMFC. We demonstrated that positively charged pyrrolinum groups of polypyrrole particles were co-interacted with sulfonic groups of Nafion as verified by FT-IR results. Mutual interaction between $Nafion-SO_3^-$ (or negatively charged Pt precursors) and Polypyrrole$-NH_2^+$ influenced the physical properties of pristine Nafion. Thermal property proton conductivity, methanol permeability, and cell performance of pristine and modified Nafion were analyzed for an application of DMFC membrane. Thermal stabilities of sulfonic groups and side chains in Nafion/Pt/polypyrrole composite membranes were higher than those of Nafion due to mutual interaction between sulfonic groups of Nafion and pyrrolinum groups of polypyrrole. Methanol permeabilities of Nafion/Pt/Polypyrrole composite were reduced more proton conductivities with the increase in the content of Pt particles. As a result of that, the enhancement of cell performance by Nafion/Pt/Polypyrole O2 relative to Nafion was more pronounced under the specific experimental condition such as high temperature and more concentrated methanol solution.

• Membrane and Water Treatment
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• v.6 no.2
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• pp.113-126
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• 2015

Salinity gradient power (SGP) systems have strong potential to generate sustainable clean electricity for 24 hours. Here, we introduce a solid-salt pressure-retarded osmosis (PRO) system using crystal salt powders rather than seawater. Solid salts have advantages such as a small storage volume, controllable solubility, high Gibbs dissolution energy, and a single type of water intake, low pretreatment costs. The power densities with 3 M draw solutions were $11W/m^2$ with exothermic energy and $8.9W/m^2$ without at 35 bar using a HTI FO membrane (water permeability $A=0.375L\;m^{-2}h^{-1}bar^{-1}$). These empirical power densities are ~13% of the theoretical value.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.764-766
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• 1998

An evaluation method for oxygen permeable characteristics of the membrane covering to each cathode of multiple cathode - single anode type dissolved oxygen sensor, which has high reproducibility and is capable of measuring multiple components in solutions. For this purpose, a measuring circuit for the multiple cathode type DO sensor was designed to lower the noise signal by adapting a digital LPF to readout the sensor output accurately. Digital LPF is designed by setting up the transfer function to set the cutoff frequency to 10Hz, and the transfer function is programmed by C language, and then the filtering characteristics are evaluated with the simulation and experiments. Using this LPF added measuring circuit for the multiple cathode type DO sensor, we have obtained the calibration factor for each cathode to calibrate the variation of the output signals. The calibration factor was obtained by measuring the sensor output signal followed by oxygen partial pressure, using the same oxygen permeable membrane at each cathode of the multiple cathode type DO sensor.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3219-3222
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• 2011

Three types of ${\beta}$-ketoacyl acyl carrier protein synthase (KAS) are important for overcoming the bacterial resistance problem. Recently, we reported the discovery of a antimicrobial flavonoid, YKAF01 (3,6-dihydroxyflavone), which exhibits antibacterial activity against Gram-positive bacteria through inhibition of ${\beta}$-ketoacyl acyl carrier protein synthase III (KAS III). In this report, we suggested that YKAF01 can be an inhibitor ${\beta}$-ketoacyl acyl carrier protein synthase I (KAS I) with dual inhibitory activity for KAS I as well as KAS III. KAS I is related to the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and can be a good therapeutic target of designing novel antibiotics. We performed docking study of Escherichia coli KAS I (ecKAS I) and YKAF01, and determined their binding model. YKAF01 binds to KAS I with high binding affinity ($2.12{\times}10^6$) and exhibited an antimicrobial activity against the multidrug-resistant E. coli with minimal inhibitory concentration (MIC) value of 512 ${\mu}g$/mL. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.1011-1019
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• 2011

The objective of this research is to evaluate optimal conditions of permeability and selectivity on the polysulfone membrane for efficiency of separation of $CH_4$ by checking four factors which are temperature, pressure, gas compositions and gas flow rates. When higher pressure was applied at the input, lower efficiency of recovery of $CH_4$ and higher efficiency of separation of $CH_4$ were shown. It has the tendency to show lower efficiency of recovery of $CH_4$ and higher efficiency of separation of $CH_4$ at the output as higher temperature at input. The lower flow rates make higher efficiency of recovery of $CH_4$ and lower efficiency of separation of $CH_4$. Finally, over 90% efficiency for $CH_4$ separation and recovery conditions are temperature ($-5^{\circ}C$), pressure (8 bar), gas composition rate (6:4) ($CH_4:CO_2$) and gas flow rate ($5\ell$/min). These conditions make higher separation and recovery efficiency such as 90.1% and 92.1%, respectively.

• Journal of Photoscience
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• v.6 no.2
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• pp.77-83
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• 1999

Calcium has a variety of functions in neuron and muscle cells and blood clotting, especially in the visual system where dark adapted rods cotransport with Na$\^$+/ into the cell. An influx of Ca$\^$++/ flows out of the cell through the Na$\^$+/-Ca$\^$++/ exchanger. By using a modified Using chamber in order to bring in vivo environment close, we have known that Ca$\^$++/ blocks the activity of guanylate cyclase, in consequence, having an effect on the amplitude of electroretinogram (ERG). We have measured the Ca$\^$++/, K$\^$+/, and Na$\^$+/ concentration in dark and light adapted bullfrog＇s (Rana catesbeiana) vitreous humor. The calcium concentration of the light adapted bullfrog＇s vitreous humor was higher than that of the dark adapted bullfrog＇s vitreous humor This means that ion activity between the photoreceptor and vitreous humor side is light dependent and we have found that a Ca$\^$++/ channel and Ca$\^$++/K$\^$+/ exchanger exist in the vitreous humor side. Taken together permeability of Ca$\^$++/, K$\^$+/ and K$\^$+/ ion internal limiting membrane faced in the vitreous humor side has light-dependent activity during the illumination.

• Journal of Microbiology and Biotechnology
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• v.18 no.12
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• pp.1997-2003
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• 2008

Cordyceps militaris is well known as a traditional medicinal mushroom and has been shown to exhibit immunostimulatory and anticancer activities. In this study, we investigated the apoptosis induced by an aqueous extract of C. militaris (AECM) via the activation of caspases and altered mitochondrial membrane permeability in human breast cancer MDA-MB-231 cells. Exposure to AECM induced apoptosis, as demonstrated by a quantitative analysis of nuclear morphological change and a flow cytometric analysis. AECM increased hyperpolarization of mitochondrial membrane potential and promoted the activation of caspases. Both the cytotoxic effect and apoptotic characteristics induced by AECM treatment were significantly inhibited by z-DEVD-fmk, a caspase-3 inhibitor, which demonstrates the important role of caspase-3 in the observed cytotoxic effect. AECM-induced apoptosis was associated with the inhibition of Akt activation in a time-dependent manner, and pretreatment with LY294002, a PI3K/Akt inhibitor, significantly increased AECM-induced apoptosis. The results indicated that AECM-induced apoptosis may relate to the activation of caspase-3 and mitochondria dysfunctions that correlate with the inactivation of Akt.

• Biomolecules & Therapeutics
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• v.10 no.3
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• pp.152-158
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• 2002

The present study elucidated the effect of $\beta$-carbolines (harmaline and harmalol) on brain mitochondlial dysfunction caused by the tyrosinase-induced oxidation of dopamine. Harmaline, harmalol and antioxidant enzymes (SOD and catalase) attenuated the dopamine-induced alteration of membrane potential, cytochrome c release and thiol oxidation in mitochondria. In contrast, antioxidant enzymes failed to reverse mitochondrial dysfunction induced by dopmnine plus tyrosinase. $\beta$-Carbolines decreased the damaging effect of dopamine plus tyrosinase against mitochondria, except no effect of harmalol on thiol oxidation. Antioxidant enzymes decreased the melanin formation from dopamine in the reaction mixture containing mitochondria but did not reduce the formation of dopamine quinone caused by tyrosinase. Both harmalol and harmaline inhibited the formation of reactive quinone and melanin. Harmalol being more effective for quinone formation and vise versa. The results indicate that compared to MAO-induced dopamine oxidation, the toxic effect of dopamine in the presence of tyrosinase against mitochondria may be accomplished by the dopamine quinone and toxic substances other than reactive oxygen species. $\beta$-Carbolines may decrease the dopamine plus tyrosinase-induced brain mitochondrial dysfunction by inhibition of the formation of reactive quinone and the change in membrane permeability.