• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.422-427
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• 2005

The $Al_2O_3$ with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite $(\beta-Al(OH)_3)$ phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of $100^{\circ}C$ per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from $100^{\circ}C\;to\; 1100^{\circ}C$, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of $Al(OH)_3{\to}{\eta}-Al_2O_3{\to}{\theta}-Al_2O_3{\to}\alpha-Al_2O_3$ sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to ${\gamma}-Al_2O_3\;at\;350^{\circ}C.$ It shows AlO(OH) ${\gamma}-Al_2O_3{\to}{\delta}-Al_2O_3{\to}{\alpha}-Al_2O_3$ sequences. The ${\gamma}-Al_2O_3$ compacted at $550^{\circ}C$ shows a high surface area $(138m^2/g)$.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.430-435
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• 2014

Physical and chemical barriers, caused by the close association of the main components of cellulosic biomass, hinder the hydrolysis of cellulose to fermentable sugars. Since the main goal of pretreatment is to increase the enzyme accessibility improving digestibility of cellulose, development of an effective pretreatment process has been considered to be important. In this study, SAA (Soaking in Aqueous Ammonia) was chosen as pretreatment because this is the simple and low-cost method. Rice straw of which the production is outstandingly high in domestic agriculture residues in Korea was chosen as raw material. SSA pretreatment with various reaction time of 3 h to 72 h was tested. The enzymatic hydrolysis and SSF (Simultaneous Saccharification and Fermentation) were performed at three different temperature (30, 40 and $50^{\circ}C$) to investigate performance of SSF upon various pretreatment conditions. As a result, this SAA treated-rice straw was found to have great potential for effective enzymatic hydrolysis and SSF with lower enzyme dosage at lower temperature ($30^{\circ}C$) than its conventional SSF. In SAA addition, SAA reduced fermentation time to 24 h owing to increase the initial hydrolysis rate substantially.

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.446-452
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• 1992

The rates of hydrolysis of aryl phenylacetates have been measured in the presence of piperidine in 80% acetonitrile-20% water(v/v). For the electron withdrawing substituents of leaving group, the hydrolysis is catalyzed by a general base and the Hammett $\rho_{LG}$ and Bronsted value $\beta$ are 5.28 and -2.72 at $30^{\circ}C$, respectively. These high senstivities of Hammett and Bronsted values are $E1_{C}B$ mechanism. But in the electron donating ones, the hydrolysis is catalyzed by a specific base and $B_{AC}2 mechanism is predominated. $pK_{SH}'s of phenylacetic acid ester and rate constants of hydrolysis $k_1$, $k_{-1)$, $k_2$ were calculated.

• Microbiology and Biotechnology Letters
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• v.8 no.1
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• pp.41-46
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• 1980

Low molecular weight endo-glucanase was partially purified from cellulase complex using Sephadex G-100 gel chromatography. Biochemical properties of the purified component was investigated. Optimum pH and temperature determined were 6.0 and 5$0^{\circ}C$, respectively. Enzymatic hydrolysis of four cellulosic substrates having varying crystallinity was evaluated. It was found that hydrolysis of amorphous region was followed by the hydrolysis of crystalline region. In order to examine the effect of adsorption of the enzyme onto the cellulosic substrates on the hydrolysis kinetics, adsorption studies were carried out. Time course of adsorption of low molecular weight endo-glucanase onto various cellulostances was observed for 25 min. The rate and amount of adsorption to amorphous cellulose was greater than those to the crystalline cellulose. This result suggested that the role of endo-glucanasc was more important to the hydrolysis of amorphous cellulose than to the crystalline region of the cellulose.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.10
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• pp.1420-1426
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• 2006

To establish a rapid and effective method for the analysis of soy isoflavone which is known to have lots of variation in derivatives of glucoside, conversion rate from isoflavone conjugates to its aglycones, and decomposition of conversed aglycones were investigated with various acid hydrolysis conditions. A number of heating conditions for acid hydrolysis including heating at convection oven $(105^{\circ}C)$, water bath $(95^{\circ}C)$, heating block $(120^{\circ}C)$, and hot plate $(120^{\circ}C)$ were applied. Acid hydrolysis in heating block with reflux was chosen as the best heating condition. From the stability test of isoflavone aglycone during acid hydrolysis, genistein, daidzein, and glycitein did not show any significant changes in their contents for 60 min of hydrolysis. Ten to thirty milligram of sample per 1 mL HCl was the best ratio of sample to acid. As conclusion, acid hydrolysis for 60 min after addition of 15 mL HCl solution to 0.5 g soybean, and then fill up to 50 mL with methanol, followed by HPLC analysis was set as a final analysis method. From this method, isoflavone contents expressed as total aglycone of feed meal was the highest with content of $1288.5{\mu}g/g$ followed by those of dehulled meal.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.758-762
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• 2019

Sodium borohydride,$NaBH_4$, has many advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFC). When PEMFC is used for marine use, $NaBH_4$ hydrolysis using seawater is economical. Therefore, in this study, hydrogen was generated by using seawater instead of distilled water in the process of hydrolysis of $NaBH_4$. Properties of $NaBH_4$ hydrolysis reaction using activated carbon supported Co-B/C catalyst were studied. The yield of hydrogen decreased as $NaBH_4$ concentration and NaOH concentration were increased during $NaBH_4$ hydrolysis using sea water. At higher concentrations of $NaBH_4$ and NaOH, byproducts adhered to the surface of the catalyst after hydrolysis reaction using sea water, reduced hydrogen yield compared to distilled water. The activation energy of $NaBH_4$ hydrolysis is 59.3, 74.4 kJ/mol for distilled water and sea water, respectively. In order to increase the hydrogen generation rate in seawater as high as distilled water, the reaction temperature has to be increased by $80^{\circ}C$ or more.

• The Korean Journal of Pesticide Science
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• v.2 no.1
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• pp.46-52
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• 1998

The hydrolysis rate of insecticidal buprofezin(IUPAC : tert-butylimino-3-isopropyl-5-phenylperhydro-1,3,5-thiadiazin-4-one) in the range of pH 2.0 and 12.0 have been examined in 15%(v/v) aqueous dioxane at $45^{\circ}C$. The hydrolysis mechanism of buprofezin is proposed from the pH-effect, solvent effect(${\ell}{\gg}m$), thermodynamic parameter(${\Delta}H^{\neq}$=11.12 $Kcal{\cdot}mol^{-1}$ &, ${\Delta}S^{\neq}=5.0e.u.$), rate equation and hydrolysis product, l-isopropyl-3-phenyl urea. General acid catalyzed hydrolysis and specific acid catalyzed($k_{H3O+}$) hydrolysis through $A-S_{E}2$ and A-2(or $A_{AC}2$) reaction mechanism with orbital-control reaction proceed below pH 8.0 and above pH 9.0, the nucleophilic addition-elimination, $Ad_{N}-E$ mechanism via tetrahedral($sp^{3}$) intermediate is initiation by general base catalyzed($k_{H2O}$) reaction. Buprofezin was more stable in alkaline ($k=10^{-8}sec.^{-1}$) than acid solutions from the sigmoid pH-rate profile. And the half-life($t=\frac{1}{2}$) of hydrolysis reaction in neutral aqueous solution(pH 7.0) at $45^{\circ}C$ was about 3 months.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.4
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• pp.533-541
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• 2016

Effect of polyphenols-rich cacao extract (CE) on lipid hydrolysis by pancreatic lipase was investigated by pH-stat digestion. Two types of substrate (oil vs. emulsion) prepared from soybean oil and CE were studied as types I and II. In the case of type I, addition of CE did not show retardation of lipid hydrolysis, showing that pancreatic lipase was not inhibited. Final digestibility rate (${\Phi}$ max, %) and initial rate (mM/s) of the 24-h aged control (52.31%, 0.03 mM/s) were similar to those of the CE-added sample (58.88%, 0.03 mM/s). However, in the case of typeII, the hydrolysis rates of the control and CE-added emulsion showed distinct differences as aging time increased to 43 days, showing lower digestion in the CE-added emulsion than the control. After 43 days, ${\Phi}$ max values of the control and CE-added emulsion were 92.13% and 77.68%, respectively.

• Korean Journal of Food Science and Technology
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• v.17 no.6
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• pp.442-446
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• 1985

The changes of nitrogen utilization ratio (NUR), Protein solution ratio (PSR) and free sugar contents during the amino acid soysauce manufacturing process by a low hydrochloric acid, temperature were investigated. On hydrolysis by 6%-HCI (3 liquor rate of defatted soybean weight, 3LR) at $85^{\circ}C$, NUR and PSR were 74.51%, 56.49% at 65 hours. At the same time free sugars were detected glucose, galactose, arabinose, fructose, xylose. on hydrolysis at $95^{\circ}C$, NUR and PSR were 77.72%, 64.04% at 50 hours, and 5 free sugars of the above statement were detected at 5 hours. Remarkable decreases in the levels of free sugars, only glucose were observed after 80 hours of the hydrolysis. On hydrolysis by 12%-HCI(3LR) at $95^{\circ}C$, NUR and IRA were 88.41%, 69.47% at 50 hours, free sugar were nearly disappeared after 20-35hours. On hydrolysis, galactose's disappearence rate was faster than glucose's.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.570-575
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• 2015

The green algae have cellulose as a main structural component of their cell wall and the cellulose content in green algae is much higher than other marine algae such as brown algae and red algae. Furthermore, green algae do not contain lignin in their cell wall and store starch as food in their plastids. Thus, it was investigated that the effect of hydrothermal pretreatment process utilizing microwave irradiation for Ulva pertusa Kjellman, a division of green algae, which is expected to be utilized for bioenergy production, on the enzymatic hydrolysis. The hydrothermal temperature have an effect on the pretreatment of Ulva pertusa Kjellman, but the effect of power of microwave irradiation is negligible. The rate of enzymatic hydrolysis was increased as the hydrothermal temperature increased until $140^{\circ}C$. The enzymatic hydrolysis of pretreated Ulva pertusa Kjellman under the optimum pretreatment conditions (50 W of microwave irradiation power and $150^{\circ}C$ of hydrothermal temperature) with cellulase, ${\alpha}$-amylase, and Novozyme 188 having ${\beta}$-glucosidase acitivity resulted in the saccharification of 96 wt% of total carbohydrate in Ulva pertusa Kjellman during 3 hrs, while it took 24 hrs for the enzymatic hydrolysis of untreated Ulva pertusa Kjellman. It confirmed that the hydrothermal pretreatment was effective on Ulva pertusa Kjellman for the enzymatic hydrolysis.