• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.712-715
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• 2001

A new combined method including the enzymatic hydrolysis of $\beta$-cyclodextrin ($\beta$-CD) and solvent extraction fo cholesterol from the hydrolyzed mixture was developed to recover cholesterol from a $\beta$-CD-cholesterol complex prepared from dairy products, such as cream, milk, and cheese. Cyclomaltodextrinase (cyclomatodextrin dextrin hydrolase, EC 3.2.1.54, DCase_ prepared form alkalophilic Bacillus sp. KJ 133 hydrolyzed the $\beta$-DC of the $\beta$-CD-cholesterol complex, and then, free cholesterol was efficiently extracted from the hydrolyzed mixture by a nonpolar solvent such as ethyl acetate. To increase the stability of free CDase, immobilized CDase was developed using sodium alginate as a carrier. The immobilized CDase showed a high recovery yield of cholesterol in a time-dependent manner compared to the free CDase. A gas chromatography analysis showed that more than 70% of cholesterol was recovered from the $\beta$-DC-cholesterol complex of cream by the immobilized CDase, whereas only 3% and 29% of cholesterol were recovered when the solvent extraction and free CDase treatment were used, respectively. The cholesterol recovered can be used as a raw material for steroid synthesis. Furthermore, this method can be an efficient way to recover cholesterol or other organic compounds that are bound in a $\beta$ -DC-cholesterol or -organic compound complex.

• 한국세라믹학회지
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• 제40권4호
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).

• 펄프종이기술
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• 제30권4호
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• pp.28-34
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• 1998

Polyvinyl acetate emulsion has been widely used as adhesives for wood and paper, paint additives and binders for fiber, leather, and other materials because it is an excellent adhesive with many advantages including low in toxicity risks and manufacturing cost. It is expected the consumption of polyvinyl acetate emulsion as adhesives will increase in cigarette industry as well as in paperboard coating industry. Recently the operation speed of the cigarette tip wrapper increased so substantially that improvement of the emulsion properties is required including good wet tack development, narrow and controlled particle size distribution, low viscosity, etc. In this study the effects of such polymerization conditions as the type and amount of emulsifier, internal or external plasticizing, and emulsification methods on the viscosity and particle size of polyvinyl acetate emulsions were examined. Results showed that polyvinyl alcohol with a high degree of hydrolysis and low molecular weight and nonionic surfactants are superior to anionic surfactant in improving adhesion and emulsion stability. They also tend to produce emulsions with smaller particle size. External plasticization with dipropylene glycol dibenzoate was more effective in improving flexibility than internal plasticization with butyl acrylate. Monomer emulsification under high shear was more effective in decreasing the particle size.

• Journal of Microbiology and Biotechnology
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• 제18권9호
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• pp.1544-1549
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• 2008

MhMTS and MhMTH are trehalose ($\alpha$-D-glucopyranosyl-[1,1]-$\alpha$-D-glucopyranose) biosynthesis genes of the thermophilic microorganism Metallosphaera hakonensis, and encode a maltooligosyltrehalose synthase (MhMTS) and a maltooligosyltrehalose trehalohydrolase (MhMTH), respectively. In this study, the two genes were fused in-frame in a recombinant DNA, and expressed in Escherichia coli to produce a bifunctional fusion enzyme, MhMTSH. Similar to the two-step reactions with MhMTS and MhMTH, the fusion enzyme catalyzed the sequential reactions on maltopentaose, maltotriosyltrehalose formation, and following hydrolysis, producing trehalose and maltotriose. Optimum conditions for the fusion enzyme-catalyzed trehalose synthesis were around $70^{\circ}C$ and pH 5.0-6.0. The MhMTSH fusion enzyme exhibited a high degree of thermostability, retaining 80% of the activity when pre-incubated at $70^{\circ}C$ for 48 h. The stability was gradually abolished by incubating the fusion enzyme at above $80^{\circ}C$. The MhMTSH fusion enzyme was active on various sizes of maltooligosaccharides, extending its substrate specificity to soluble starch, the most abundant natural source of trehalose production.

• Journal of Microbiology and Biotechnology
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• 제14권5호
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• pp.1014-1021
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• 2004

Two thermostable xylanases, designated XynA and XynB, were purified to homogeneity from the culture supernatant of Paenibacillus sp. DG-22 by ion-exchange and gel-filtration chromatography. The molecular masses of xylanases A and B were 20 and 30 kDa, respectively, as determined by SDS-PAGE, and their isoelectric points were 9.1 and 8.9, respectively. Both enzymes had similar pH and temperature optima (pH 5.0-6.5 and $70^{\circ}C$), but their stability at various temperatures differed. Xylanase B was comparatively more stable than xylanase A at higher temperatures. Xylanases A and B differed in their $K_m$ and $V_{max}$ values. XynA had a $K_m$ of 2.0 mg/ml and a $V_{max}$ of 2,553 U/mg, whereas XynB had a K_m$ of 1.2 mg/ml and a $V_{max}$, of 754 U/mg. Both enzymes were endo-acting, as revealed by their hydrolysis product profiles on birchwood xylan, but showed different modes of action. Xylotriose was the major product of XynA activity, whereas XynB produced mainly xylobiose. These enzymes utilized small oligosaccharides such as xylotriose and xylotetraose as substrates, but did not hydrolyzed xylobiose. The amino terminal sequences of XynA and XynB were determined. Xylanase A showed high similarity with low molecular mass xylanases of family 11.

• The Korean Journal of Ceramics
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• 제1권3호
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• pp.137-142
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• 1995

Monodispersed $Al_2O_3-TiO_2$ Powder was prepared by metal-alkoxide hydrolsis. A homogeneous nucleation/growth occurred in the solutions containing ethanol, butanol and acetonitrile, and resulted in spherical, submicrometer-sized powder. The titania and the alumina crystals were formed at $800^{\circ}C$ and $1000^{\circ}C$, respectively. These crystala were subsequently reacted each other beyond $1320^{\circ}C$ and formed $Al_2TiO_5$. The relative densities of sintered bodies prepared with as-received powder were examined at the temperature range of 1300-$1500^{\circ}C$ and they were about 79% at $1300^{\circ}C$. The formation of aluminum titanata decreased the relative density at the temperature range of 1300-$1450^{\circ}C$, and at above $1450^{\circ}C$, the relative density started to increase again. It was observed that $\alpha-Al_2O_3$-doped aluminum titanate was more stable than pure aluminum titante at $1200^{\circ}C$.

• Journal of Dairy Science and Biotechnology
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• 제31권1호
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• pp.67-73
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• 2013

Food allergy is defined as adverse reactions toward food mediated by aberrant immune mechanisms. Cow's milk allergy is one of the most common food allergies in childhood. This allergy is normally outgrown in the first year of life, however 15% of allergic children remain allergic. Cow's milk allergy seem to be associated with casein (${\alpha}_{s1}$-CN), ${\beta}$-lactoglobulin and whey protein. In addition to this, many other milk proteins are antigenic and capable of inducing immune responses. Various food processing affects the stability, structure and intermolecular interactions of cow milk proteins, as a result reduction the allergenic capacity. Heating, hydrolysis, chemical, proteolytic and other processes such as gamma-ray irradiation, high pressure, using probiotics treatments of milk to obtain hypoallergenic milk have been developed to reduce allergic reactions.

• 한국응용과학기술학회지
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• 제11권2호
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• pp.121-127
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• 1994

1-(2-hydroxyethyl)-2-undecyl-2-imidazoline[I] was converted into various types of sulfonated or sulfated amphoteric surfactants as following. 1-(2-hydroxyethyl)-1-(3-sulfonatedpropyl)-2-undecyl-2-imidazolium[III] 1-(2-sulfatedethyl)-1-methyl-2-undecyl-2-imidazolium[IV] 1-dioxylethylene methyl sulfonated-1-methyl-2-undecyl-2-imidazoliun[V] N-[N'-(2-hydroxyethyl)-N-(3-sulfonatedpropylammonio]ethyl dodecanoyl amide[VI] Mono sodium N-[N'-(2-hydroxyethyl)-N'-disulfonatedpropylammonio]ethyl dodecanoyl amide[VII] N-[N'-(2-hydroxyethyl-N'-(2-hydroxypropl-N'(3-sulfonatedpropyl)ammonio] ethyl dodecanoyl amide[VIII] The alkylimidazolines could be readily hydrolyzed to give amidoamines, but by quaternerization, hydrolysis stability of imidazoline and amide type amphoteric surfactantes were increased in the alkali and acid conditions. Also, at least three carbon chains introduce to the main group, water solubility was sparingly increased.

• 대한화학회지
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• 제12권3호
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• pp.121-127
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• 1968

In the oligomerization of p-aminophenol under the catalytic action of the metallic complexes, the effects of the ligands are studied. When the initial velocity of $O_2$ uptake at pH 8 using Fe(Ⅲ) as the central metal and N-hydroxylethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,2-cyclohexanediaminetetraacetic acid(CyDTA) as the ligands respectively are compared, the velocities are as the following order: HEDTA > EDTA > DTPA > CyDTA. Further when the effect of the ligands, nitrilotriacetic acid (NTA), HEDTA, EDTA, and DTPA, on the yields of oligomers are compared, the result shows as the following order: NTA > HEDTA > EDTA > DTPA. These are nearly reverse order of the stability constants of the complexes. In order to determine the composition of the mixed complexes at the initial step, the method of continuous variation is used, and it is found that the composition ratio of Fe-EDTA complex to monomer in the mixed complexes is one at pH 5-8 range. It is also found that at pH 9 or in the more alkaline range, side reactions occur to form water soluble dimer of quinone type and the catalytic action of the metallic complex markedly decreases on account of the hydrolysis of the central metal by the $OH^-$ ion.

• Journal of Microbiology
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• 제43권6호
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• pp.561-568
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• 2005

A newly-isolated thermophilic strain of the zygomycete fungus Rhizomucor pusillus 13.36 produced highly active dextrinogenic and saccharogenic enzymes. Cassava pulp was a good alternative substrate for amylase production. Dextrinogenic and saccharogenic amylases exhibited optimum activities at a pH of 4.0-4.5 and 5.0 respectively and at a temperature of $75^{\circ}C$. The enzymes were highly thermostable, with no detectable loss of saccharogenic or dextrinogenic activity after 1 hand 6 h at $60^{\circ}C$, respectively. The saccharogenic activity was inhibited by $Ca^{2+}$ while the dextrinogenic was indifferent to this ion. Both activities were inhibited by $Fe^{2+}\;and\;Cu^{2+}$ Hydrolysis of soluble starch by the crude enzyme yielded $66\%$ glucose, $19.5\%$ maltose, $7.7\%$ maltotriose and $6.6\%$ oligosaccharides.