• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.284-290
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• 2019

Ternary MoS₂/graphene (G)-TiO₂ photocatalysts were prepared by a simple hydrothermal method. The morphology, phase structure, band gap, and catalytic properties of the prepared samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis spectrophotometry, and Brunauer-Emmett-Teller surface area measurement. The H₂ production efficiency of the prepared catalysts was tested in methanol-water mixture under visible light. MoS₂/G-TiO₂ exhibited the highest activity for photocatalytic H₂ production. For 5 wt.% and 1 wt.% MoS₂ and graphene (5MT-1G), the production rate of H₂ was as high as 1989 µmol^-1h^-1. The catalyst 5MT-1G showed H₂ production activity that was ~ 11.3, 5.6, and 4.1 times higher than those of pure TiO₂, 1GT, and 5MT, respectively. The unique structure and morphology of the MoS₂/G-TiO₂ photocatalyst contributed to its improved hydrogen production efficiency under visible light.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.228-234
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• 2006

The culture conditions were investigated to maximize the production of laccase from Fomitella fraxinea mycelia. Among the tested media, mushroom complete medium (MCM) showed the highest production of the enzyme. The optimum culture medium was 2% dextrose, 0.4% $(NH_4)_{2}HPO_4$, 0.05% $Na_{2}HPO_{4}{\cdot}7H_{2}O$, and 0.05% KCl as carbon, nitrogen, phosphorus, and inorganic salt sources respectively. SDS-PAGE followed by laccase activity staining using 2,6-djmethoxyphenol as the substrate was performed to identify the laccase activity under culture conditions studied. Zymogram analysis of the culture supernatant showed a laccase band with a molecular mass of 50 kDa. The enzyme production from F. fraxinea was reached to the highest level after the cultivation for 10 days at $25^{\circ}C$ and initial pH 8. The enzyme activity of the culture supernatant was most active at $50^{\circ}C$ and pH 5.

• Microbiology and Biotechnology Letters
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• v.9 no.2
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• pp.91-97
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• 1981

A thermophilic soil isolate Bacillus sp. Y-127 was selected for the production of thermostable amylase. The strain was used for the enzyme production and the thermostable amylase was characterized. The optimum cultural conditions for the enzyme production were 6$0^{\circ}C$ at pH 7.0 for 32 hours using a mineral medium containing 2% soluble starch and 0.2% yeast extract. The extra-cellular enzyme was purified about 123-folds with about 6% recovery. The purified enzyme was stable at pH between 4.0 and 7.0, and temperature up to 6$0^{\circ}C$.

• Journal of Plant Biology
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• v.37 no.3
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• pp.271-276
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• 1994

The possibility that 1-aminocyclopropane-1-carboxylic acid (ACC)-uptake may be dependent on the H+-gradient established across the plsma membrane was tested in protoplasts isolated from 2.5 day old mungbean hypocotyls. The ACC-induced ethylene production was inhibited when the H+-gradient was collapsed by the treatment with carbonycyamide-p-trifluro-methoxy-phenylhydrazone (FCCP). Moreover, the treatment with o-vanadate, a specific inhibitor of plasma membrane H+-ATPase, caused the inhibition of ethylene production. The ACC-induced ethylene production was inhibited by the treatemnt with verapamil (Ca2+-channel blocker), or ethylene glycol-bis($\beta$-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) (Ca2+-chelator). In contrast, the ehtylene production was stimulated by the application of A23187 (Ca2+ ionophore). The inhibitory effect of EGTA in the ethylene producton was magnified in the presence of A23187. From these results, we suggest that the external Ca2+ influx to the cytosol resulted in the stimulatin of ACC oxidase activity after ACC-uptake resulting from a H+-gradient across the plasma membrane.

• Journal of Life Science
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• v.9 no.2
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• pp.5-8
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• 1999

We isolated a sphingonyelinase (SMase) inhibitor, which would be a potential reagent to regulate cell proliferation, oncogenesis, and inflammation, from a strain of Streptomyces sp.. In this paper, we report the optimal conditions for the production of SMase inhibitor, designed as sphinin, from Streptomyces sp. F50970. The optimal carbon and nitrogen source were 1% soluble starch and 0.05%-0.15% trypton. Most of monosaccharides and high concentration of soluble starch above 1.0% caused falling of pH and sphinin production. Zn2+, Cu2+, Fe2+, Mn2+, and Co2+inhibited cell growth and the production of sphinin. Inorganic phosphate promoted the sphinin production. Optimal initial pH for the production of sphinin was 7.5-8.0. Addition of CaCO3 to the medium resulted in an increase of inhibitor production. Based on these results, we designed a fermentation medium for the production of a SMase inhibitor, sphinin, from Streptomyces sp. F50970.

• KSBB Journal
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• v.4 no.2
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• pp.134-142
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• 1989

In exopolysaccharide fermentation by Aureobasidium pulluans, the effects culture conditions (concentration of nitrogen, potassium phosphate, dissolved oxygen, and initial pH) on the production of exopolysaccharide and the appearance of melanin pigment were investigated. The results are as follows. (1) The specific growth rate and the specific production rate of exopolysaccharide were inhibited by substrate when the carbon source concentration higher than $50g\;/\;{\ell}$ and the cell growth increased with increases of nitrogen source but exopolysaccharide production decreased with the nitrogen concentration when it become greater than $1\;g\;/\;{\ell}$. (2) The maximum cell growth and the maximum exopolysaccharide production were obtained at initial pH values of 3.0 and 7.5 respectively. As the initial pH increased, the yeast-like cells increased and the increased of dissolved oxygen increased the cell growth and exopolysaccharide production. (3) As the concentration of dissolved oxygen is increased or the concentration of nitrogen source is decreased, the period of melanin pigment appearance becomes shorter and the melanin pigment never appeared when the initial pH was less than 3.0 or the potassium phosphate was not added.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.129-136
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• 2003

Numerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added $CO_{2}$ and $H_{2}O$ to fuel- and oxidizer-sides on flame structure and NO emission behavior in $CH_{4}$/Air counterflow diffusion flames. The dilution with $H_{2}O$ results in significantly higher flame temperatures and NO emission, but dilution with $CO_{2}$ has much more chemical effects than that with $H_{2}O$. Maximum reaction rate of principal chain branching reaction due to chemical effects decreases with added $CO_{2}$. but increases with added $H_{2}O$. The NO emission behavior is closely related to the production rate of OH, CH and N. The OH radical production rate increases with added $H_{2}O$ but those of CH, N decrease. On the other hand the production rates of OR CH and N decrease with added $CO_{2}$. It is found that NO emission behavior is considerably affected by chemical effects of added $CO_{2}$ and $H_{2}O$.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.458-463
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• 2007

An experimental study on scale-up of Electro-electrodialysis(EED) to increase the efficiency of HI decomposition section in the IS(Iodine-Sulfur) process was carried out. The EED stack extends the effective area of the membrane to 20 times of that formerly used in a single EED unit cell. The experiment was carried out using HIx solution($HI:H_2O:I_2=1:8.4{\sim}9:1.85{\sim}1.9$) at $100^{\circ}C$ and various solution flow rates of 20, 30, 40 and 50 cc/min. The increased HI molality in catholyte after one-pass throughout from the EED stack was 3 mol/kg-$H_2O$, 2.2 mol/kg-$H_2O$, 2 mol/kg-$H_2O$ and 1.37 mol/kg-$H_2O$ at 20, 30, 40 and 50 cc/min, respectively. These values satisfied the target of HI molality(the increase of HI molality: 2 mol/kg-$H_2O$) in the IS process for hydrogen production of 20 L/hr.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.1
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• pp.72-79
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• 2006

Kojic acid production by Aspergillus flavus strain S44-1 using sucrose as a carbon source was carried out in a 250-mL shake flask and a 2-L stirred tank fermenter. For comparison, production of kojic acid using glucose, fructose and its mixture was also carried out. Kojic acid production in shake flask fermentation was 25.8 g/L using glucose as the sole carbon source, 23.6 g/L with sucrose, and 6.4 g/L from fructose. Reduced kojic acid production (13.5 g/L) was observed when a combination of glucose and fructose was used as a carbon source. The highest production of kojic acid (40.2 g/L) was obtained from 150 g/L sucrose in a 2 L fermenter, while the lowest kojic acid production (10.3 g/L) was seen in fermentation using fructose as the sole carbon source. The experimental data from batch fermentation and resuspended cell system was analysed in order to form the basis for a kinetic model of the process. An unstructured model based on logistic and Luedeking-Piret equations was found suitable to describe the growth, substrate consumption, and efficiency of kojic acid production by A. flavus in batch fermentation using sucrose. From this model, it was found that kojic acid production by A. flavus was not a growth-associated process. Fermentation without pH control (from an initial culture pH of 3.0) showed higher kojic acid production than single-phase pH-controlled fermentation (pH 2.5, 2.75, and 3.0).

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.1
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• pp.17-22
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• 2004

A bacterial strain WJ-98 found to produce active extracellular keratinase was isolated from the soil of a poultry factory. It was identified as Paracoccus sp. based on its 16S rRNA sequence analysis, morphological and physiological characteristics. The optimal culture conditions for the production of keratinase by Paracoccus sp. WJ-98 were investigated. The optimal medium composition for keratinase production was determined to be 1.0% keratin, 0.05% urea and NaCl, 0.03% K$_2$HPO$_4$, 0.04% KH$_2$PO$_4$, and 0.01% MgCl$_2$$.$6H$_2$O. Optimal initial pH and temperature for the production of keratinase were 7.5 and 37$^{\circ}C$, respectively. The maximum keratinase production of 90 U/mL was reached after 84 h of cultivation under the optimal culturing conditions. The keratinase from Paracoccus sp. WJ-98 was partially purified from a culture broth by using ammonium sulfate precipitation, ion-exchange chromatography on DEAE-cellulose, followed by gel filtration chromatography on Sephadex G-75. Optimum pH and temperature for the enzyme reaction were pH 6.8 and 50$^{\circ}C$, respectively and the enzymes were stable in the pH range from 6.0 to 8.0 and below 50$^{\circ}C$. The enzyme activity was significantly inhibited by EDTA, Zn$\^$2+/ and Hg$\^$2+/. Inquiry into the characteristics of keratinase production from these bacteria may yield useful agricultural feed processing applications.