• Journal of the Korean Applied Science and Technology
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• v.28 no.3
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• pp.284-289
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• 2011

All spectroscopic methods used in this work indicate the instability of tungstophosphates in aqueous solutions and considerable dependence on pH with regard to the dominant species present in the solution. UV spectroscopy indicates that some changes occur in the system but they cannot be specified. IR spectroscopy gives more information on the identification of the dominant species as a function the pH of the solution. NMR spectroscopy provides unique data, which can be used for more accurate interpretation of changes in the solution of various pH values. In the case of aqueous solutions of tungstophosphates, the parent anion was present only in a very acidic solution of ca. pH 1. Some differences in interpretation of the molecular species present under various experimental conditions can be ascribed to some extent to the diversity of chemical shifts of NMR. Under physiological conditions attained with the addition of NaOH, tungstophosphates was dominantly present in the form of the lacunary monovacant anion.

• Current Research on Agriculture and Life Sciences
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• v.28
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• pp.9-15
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• 2010

Extraction Efficiency of colorants from sorghum and its storage stability were examined according to the various extracting and storage conditions in this study. The obtained results were as follows ; The absorbance values of extracted colorants were increased with increasing extract time and temperature. The extraction at pH 4 extract was most efficient among the various pH conditions. In the juice extractor system, the amount of extracted colorant was more in distilled water pre-treatment than pH 5, but it was more in pH 5 in the long time pre-treatment above 20 hour. The color of extract solutions changed through variation of the pH. Its color changed from light yellow to heavy yellow finally red ton by pH increasing. The Methionine addition gave an effect on the storage stability of colorant solution and then had better storage stability. And so it delayed the color change up to storge period 18th day and the stabilizing effect was revealed in order of Methionine 10mmol-addition>20mmol-addtion>non-addtion.

• Korean Journal of Environmental Biology
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• v.32 no.4
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• pp.306-310
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• 2014

The brown seaweed Sargassum fusiforme is an edible and highly valued in Korea. During the summer season, phytal organisms graze heavily on young algal blades and holdfastsof the species and substantially reduce harvestable biomass. Here, in this study, we investigated the effects of pH (range: 2~13) and salinity (range: 0~44 psu) on the removal of two major phytal animals, Caprella scaura and Gammaropsis utinomi, associated with S. fusiforme. We also examined the optimum quantum yield (Fv/Fm) of algae in the same experimental conditions to quantify the tolerance of algae to acid and salinity treatments. It was observed that the phytal animals showed more than 80% mortality at pH lower that pH 4 and the extreams of salinity (0~10 psu and 44 psu) after a 5 min of immersion. However, the quantum yield of S. fusiforme was not significantly different from controls within the pH 3~11 range, and the 0~44 psu salinity range. Precisely, if the pH and salinity conditions outside these ranges were used in comercial Sargassum culture, the removal of the animal species would be higher, but with reduced quantum yield of algae. Taken together, our study results indicated that the pH and salinity treatments could allow multiple harvests from the same holdfast of S. fusiforme.

• The Korean Journal of Food And Nutrition
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• v.10 no.2
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• pp.241-245
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• 1997

In order to make natural food color from Gardenia, we investigated optimal conditions of color extraction, and thermal stability and light stability of color extracted compared with Yellow-4. In case of ethanol extraction, optimal conditions for color extraction were substrate 10%, 4$0^{\circ}C$, pH 7.0 and 42rs, respectively. In case of water extraction, optimal conditions for color extraction were substrate 10%, 7$0^{\circ}C$, pH 7.0 and 48hrs, respectively. Extraction yield in the optimal conditions was 75% in ethanol and 63% in water. The thermal stability and light stability of Yellow-4 were both upper 98%, but those of Gardenia yellow color were 62 and 90%, respectively.

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of Environmental Science International
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• v.17 no.3
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• pp.275-285
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• 2008

The floc formation, breakage and reformation of humic acid by inorganic (alum and PAC) and organic coagulants (cationic polyelectrolytes) at several conditions (pH, ionic strength and floc breakage time) were examined and compared among the coagulants at different conditions using a continuous optical monitoring method, with controlled mixing and stirring conditions. For alum, the shapes of formation, breakage and reformation curves at different pH (5 and 7) were different, but the shapes and the sizes of initial floc and reformed floc were nearly the same in the absence and presence of electrolytes at pH 7. For PAC, similar shapes of the curves were obtained at different pH and ionic strength, but the sizes were different, except for those of reformed flocs at different pH. However, for these coagulants, reformed flocs after floc breakage, occurred irreversibly for all the conditions used in this study. For organic coagulants, the time to attain the initial plateau floc size, the extent of floc strength at high shear rate and reversibility of reformed floes were different, depending floc formation mechanism. Especially, for the cationic polyelectrolyte forming humic flocs by charge neutralization or electrostatic patch effect mechanism, reformed flocs occurred reversibly, regardless of pH and floc breakage time, but occurred irreversibly in the presence of electrolytes.

• Journal of Environmental Health Sciences
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• v.31 no.6
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• pp.498-503
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• 2005

Stability of soybean isoflavone isomers according to extraction conditions such as temperature, pH, and extracting solvents was investigated. Heating induced three chemical reactions to occur for malony1 derivatives of isoflavones, namely decarboxylation of malony1 groups into acety1 derivatives, deesterification of malony1 residues, and hydrolysis of $\beta$-glycosidic bonds. Among the twelve isoflavone isomers, change in concentrations of acety1glycosides were most pronounced: Acety1 derivatives were present only in trace amounts in unheated hypocotyls, but the content increased dramatically during heating. As for the glycosides, concentrations of daidzin and glycitin increased due to heat treatment, though that of genistin remained almost unchanged. Heat decomposition rates and the patterns differed among the three malony1 derivatives. After 120 min at $80^{circ}C$, the relative concentrations of daidzin, glycitin and genistin were increased from $9.2\%$, $12.4\%$ and $3.3\%$ to $19.3\%$, $21.9\%$ and $6.2\%$, respectively. When crude isoflavones were solubilized in glycine buffer (pH 10.0) and incubated at $80^{circ}C$, deesterification occurred faster than at pH 7.0. When the pH of isoflavone solution was increased, the malony1glycosides were hydrolyzed to their respective glycosides at increased rate. Both acetyl and aglycone forms were unchanged and only de-esterification reactions occurred. At the acidic pH, malonylglycosides were much stable both at 60 and $80^{circ}C$. However at pH 10, $80^{circ}C$ and 1 hr, $75-80\%$ of malonylglycosides were transformed to their deesterified glycosides. When isoflavones were extracted with $60\%$ aqueous ethanol at $60^{circ}C$, isoflavone isomers were stable and the deesterification reactions did not occur in these conditions. However, at $80^{circ}C$ deesterification of malonyiglycosides occurred significantly with $15-20\%$ of malonylglycosides being hydrolyzed into their respective glycosides. This experiment showed that malonylglycosides undergo decomposition when heated or exposed to alkaline conditions. Also, aqueous ethanol was preferred to aqueous methanol as solubilizing media for obtaining extract with minimum degradation of malonylglycosides.

• Journal of Ginseng Research
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• v.24 no.2
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• pp.58-63
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• 2000

To develop the production of ginseng root using plant tissue culture technology, submerged culture conditions were optimized by means of the fractional factorial design with 4 factors and 3 levels by a RSM computer program. The ginseng (Panax ginseng C. A. Meyer) roots induced by plant growth regulators were cultured on SH medium and the effects of various pH of medium, sucrose concentration, nitrogen concentration and phosphate concentration on fresh weight of the ginseng root were investigated. The fresh weight of ginseng root increased with a decrease in nitrogen concentration and fresh weight of ginseng root varied from 1.00 to 2.33g under various conditions. The optimum pH of medium and sucrose concentration determined by a partial differentiation of the model equation, nitrogen and phosphate concentration were pH 5.6, sucrose 3.8%, nitrogen 50 mg/L and phosphate 80.7 mg/L, respectively. Under these conditions, the predicted growth of ginseng root was estimated to be 2.36g.

• Journal of The Korean Society of Grassland and Forage Science
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• v.7 no.1
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• pp.1-7
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• 1987

A pot experiment conducted to investigate the root elongation and weight of grasses, i.e. Orchardgrass, tall fescue and perennial ryegrass under the conditions adjusted pH of half vertical part of pot soil to seven levels from 2 to 8. 1. Root growth was drastically decreased as soil pH was lowed. 2. Higer the soil pH, longer the root length. Increase of soil pH to 6 increased the root length of orchardgrass, perennial ryegrass and tall fescue. 3. Regardless of grass species, most of roots distributed to the soil which adjusted pH from 6 to 7. 4. Dry weight of root was increased to pH 7 of soil in orchardgrass and perennial ryegrass and was 55 to 78% of production of pH 6 compared with soil pH 7. In case of tall fescue, dry root weight in the soil pH 7 was 69.8% of root weight growed in soil pH 6.

• Corrosion Science and Technology
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• v.4 no.6
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• pp.236-241
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• 2005

Hydrogen induced cracking (HIC) is one of the hydrogen degradation phenomena of linepipe steels caused by $H_2S$ gas in the crude oil or natural gas. However, NACE TM0284-96 standard HIC test method is hard to satisfy the steel requirements for sour service application since it uses more severe environmental conditions than actual conditions. Therefore, in order to use steels effectively, it is required to evaluate HIC resistance of steels in the practical range of environmental severity. In this study, HIC resistance of two high strength low alloy (HSLA) steels being used as line pipe steels was evaluated in various test solutions with different $H_2S$ pressures and pH values. The results showed that the key parameter affecting crack area ratio (CAR) is $H_2S$ partial pressure of test solution when the pH value of test solution is not over 4. Hydrogen diffusivity was not a constant value, but it was rather affected by the hydrogen ion concentration (pH value) in the solution.