• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.266-272
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• 2020

In this study, the production of ethyl levulinate from chitosan using successive acid-catalyzed hydrolysis and esterification was investigated. To optimize and analysis the reaction factors and heir reciprocal interaction, response surface methodology was introduced. In the effect of water content in ethanol solvent, the production yield of ethyl levulinate was high at 5% water content (or 95% ethanol). As a result of optimization of reaction factors, 30.1% ethyl levulinate yield was obtained under the condition of 200 ℃, 3.19% chitosan, 0.49M sulfuric acid, 5% water content, and 58 min. Finally, the formation yield of ethyl levulinate was tended to enhance by increase of combined severity factor. This result indicated that the potential of chitosan as feedstock for production of chemicals and fuels.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.211-224
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• 2008

Characteristics of the esterification reaction between free fatty acid in rice bran oil and methanol was investigated in the presence of catalysts, such as PTS(p-toluene sulfonic acid), Amberlyst 15 dry and SCX(silica gel based strong cation exchange resin). While reaction temperature was kept constant at $65^{\circ}C$, initial feed content of free fatty acid was varied from 100% to 1% by addition of pure free fatty acid which was previously made from rice bran oil. Also, the effect of mole ratio of methanol to fatty acid on the final conversion was examined. When esterification of pure free fatty acid was catalyzed by several acids, final conversions were increased in order of Amberlyst 15 dry, SCX and PTS. Using PTS catalyst, initially the reaction proceeded in homogeneous 2nd oder reaction mechanism. However, phase of reaction mixture changed from homogeneous to heterogeneous along the reaction time and then reaction rate was retarded by mass transfer resistance of methanol. Final conversion of free fatty acid in reaction mixture was depended on initial feed content of free fatty acid, and had maximum value at 30% of initial feed free fatty acid content for all kinds of catalysts used. And the final conversion was increased with mole ratio of methanol by the improvement of reaction rate. When initial feed free fatty acid content below 10% and the reaction was catalyzed by PTS, concentration of free fatty acid in reaction mixture was increased in the middle of reaction time by hydrolysis of triglyceride in reaction mixture. Also, if silica gel was added into the reaction mixture which had initial feed free fatty acid content below 50%, final conversion was increased by the adsorption of moisture produced. The SCX catalyst made the esterification reaction of free fatty acid to progress like in case of PTS catalyst. However, when initial feed free fatty acid content below 10%, concentration of free fatty acid in. reaction mixture was decreased monotonically and not increased in the middle of reaction time on the contrary to the case of PTS. Thus, SCX catalyst accomplished more high value of final conversion than PTS catalyst for the initial feed fatty acid content range from 50% to 5% In case of initial feed free fatty acid content of 1% and mole ratio of methanol was 2, concentration of free fatty acid in reaction mixture increased over the initial feed free fatty acid content for all kind of catalysts used. Although SCX catalyst was added into reaction mixture which had 1% of initial feed fatty acid content, final conversion was hardly raised by mole ratio of methanol.

• YAKHAK HOEJI
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• v.27 no.3
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• pp.185-205
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• 1983

Penicillins and cephalosporins are biosynthesized from L-.alpha.-aminoadipic acid, L-cysteine and L-valine. A tripeptide, LLD-$\delta$-($\alpha$-aminoadipyl)cysteinylvaline(LLD-ACV) was isolated from fermentation broths of Cephalosporium acremonium as well as of Penicillium chrysogenum and it was proved that the LL-$\delta$-($\alpha$-aminoadipyl cysteine was formed first in mycelia, to which valine would be connected to give LLD-ACV. However, several points are still unsolved; first, what mechanism is involved in the configurational change from L-valine to D-valine, second, what kind of cyclization mechanism gives a $\betha$-lactam ring and a thiazolidine ring and third, what is the pathways for the ring expansion from penicillins to cephalosporins. At present, it seems clear that LLD-ACV is cyclized to give isopenicillin N, which is transformed to penicillin N and further to cepbalosporin C. Other hydrophobic penicillins, including benzyl penicillin and penicillin V, are formed from isopenicillin N by acyl-exchange reactions catalyzed by penicillin transferase, rather than by acylation reaction on 6-aminopenicillanic acid(6-APA), which was isolated from the fermentation broth of P. chrysogenum and which would be formed by hydrolysis of $\delta-(\alpha$-amincadipyl)amido moiety at the C-6 position in isopenicillin N or penicillin N by penicillin acylase. Acylation of 6-APA is catalyzed also by penicillin acylase, but the reaction is proved not to be involved in penicillin biosynthesis. Understanding the biosynthesis of penicillins and cephalsoporins would provide solutions to increase in fermentation yields of penicillins, especially of cephalosporins and a solution to biological production of 7-aminocepbalosporanic acid (7-ACA) which is of importance in pharmaceutical industry. Still regulation mechanisms in penicillin and cephalosporin biosynthesis are unveiled at all.

• Journal of the Korean Chemical Society
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• v.59 no.3
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• pp.238-245
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• 2015

The crystallization and morphology change of amorphous titanias by hydrothermal treatment have been investigated. The amorphous titanias were prepared by pure water hydrolysis of two different precursors, titanium tetraisopropoxide (TTIP) and TTIP modified with acetic acid (HOAc) and characterized prior to hydrothermal treatment. In order to avoid complicate situation, the hydrothermal treatment was performed in a single solvent water with and without strong acids at various temperatures. The effects of strong acid, temperature and time were systematically investigated on the transformation of amorphous titania to crystalline TiO₂ under simple hydrothermal condition. Without strong acid the titanias were transformed into only anatase phase nanoparticle regardless of precursor type, temperature and time herein used (up to 250 ℃ and 48 hours). The treatment temperature and time effected only on the crystalline size, not on the crystal phase et al. However, it was clearly revealed that the strong acids such as HNO₃ and HCl catalyzed the formation of rutile phase depending on temperature. HCl was slightly better than HNO₃ in this catalytic activity. The morphology of rutile TiO₂ formed was also a little affected by the type of acid. The precursor modifier, HOAc slightly reduced the catalytic activity of the strong acids in rutile phase formation.

• Archives of Pharmacal Research
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• v.27 no.7
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• pp.742-750
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• 2004

This paper for the first time reports the isolation of 5 compounds from Phellinus linteus. A sphingolipid (1) and two tyrosinase inhibitory compounds (2, 3) along with two carboxylic acids (4, 5), were isolated from the fruiting body of Phellinus linteus (Berk ＆ Curt) Aoshima. The structure of compound 1 was identified as 1-O-$\beta$-D-glucopyranosyl-(2S, 3R, 4E, 8E)-2-[(2R)-2-hydroxyhexadecanoylamino]-9-methyl-4,8-octadecadiene-1,3-diol, known as cerebroside B, based on spectroscopic methods such as 1D and 2D NMR as well as by acid hydrolysis. Compounds 2-5 were identified as protocatechualdehyde (2), 5-hydroxymethyl-2-furaldehyde (HMF) (3), succinic acid (4), and fumaric acid (5) based on the spectroscopic evidence. Compounds 2 and 3 inhibited the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with an $IC_{50}$ of 0.40 and 90.8 $\mu\textrm{g}$/mL, respectively. The inhibitory kinetics, which were analyzed by the Lineweaver-Burk plots, were found to be competitive and noncompetitive inhibitors with a $K_{j}$ of 1.1 $\mu\textrm{m}$ and 1.4 mM, respectively.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.1
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• pp.72-78
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• 2000

The major cause of paper deterioration is the acid-catalyzed hydrolysis of the cellulose in paper fibres. The deacidification of paper reduced the rate of this deterioration, and it has been reported to extend the useful life of acidic paper by three to five times. It has been recognized the need for an effective method of deacidifying large quantities of books and documents. T도 review of the current state of deacidification technology has been published recently. The paper points to the immediate need for a cost-effective and reliable method to save the millions of books that prish every year. It was tried to deacidify by the gaseous ethanolamine for solving with the above the problem. Acidic paper was treated with the monoethanolamine, diethanolamine, triehtanolamine. It result, it was found that the rate of deacidification was in caused very little grightness and fold endurances. For solving this problem, it was carried with deacidify by combination treatment of the various gaseous ehtnaloamines. In result, decreasing of brightness and fold endurance is reduced.

• Journal of the Korean Chemical Society
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• v.34 no.3
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• pp.297-303
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• 1990

$VO^{2+}-catalyzed oxidation of n-butylamine by hydrogen peroxide shows that the reaction is a first order in the concentration of n-butylamine, acid added, and VO^{2+}$ as catalyst, respectively. The reactions involve the initial formation of an imine intermediate, followed by hydrolysis to butyraldehyde and ammonia. It is suggested that the rate-determining step is a process dehydrogenation of n-butylammine.

• Journal of Pharmaceutical Investigation
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• v.20 no.3
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• pp.145-152
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• 1990

Zirconium pyrithione complex was prepared by reaction of sodium-pyrithione solution and zirconyl chloride solution. The physico-chemical properties of the complex was examined by means of IR, XRD, DSC and NMR. And the stability of Zr-complex was investigated on the basis of accelerated stability analysis under conditions of temp. elevation, UV radiation and pH dependence. The result indicates that the ratio of the ligand to metal in Zr-pyrithione complex was determined 4:1, and its stability constant was $4.643{\times}10^4$. The rate order of decomposition of the complex was apparent first-order reaction of which rate constant and the decomposition rate was not only accelerated by effect of heat and UV radiation but was catalyzed by specific acid-base catalysis considered the pH dependence for the hydrolysis of the complex and the suspension was most stable over the range pH 4-8 indicating that solvent catalysis is the primary made of reaction in this region.

• Journal of Applied Biological Chemistry
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• v.43 no.4
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• pp.240-245
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• 2000

Two genes encoding maltooligosyltrehalose synthase (SaMTS) and maltooligosyltrehalose trehalohydrolase (SaMTH) were isolated from a hyperthermophilic microorganism, Sulfolobus acidocaldarius (ATCC 49462). ORFs of the SaMTS and SaMTH genes are 2,163 and 1,671 bp long and encode 720 and 556 amino acid residues, respectively. A bifunctional fusion enzyme (SaMTSH) was constructed through the gene fusion of SaMTS and SaMTH. Recombinant SaMTS, SaMTH, and SaMTSH fusion enzyme were overexpressed in E. coli BL21. SaMTS and SaMTH produced trehalose and maltotriose from maltopentaose in a sequential reaction. SaMTSH fusion enzyme catalyzed the sequential reaction in which the formation of maltotriosyltrehalose was followed by hydrolysis leading to the synthesis of trehalose and maltotriose. The SaMTSH fusion enzyme showed the highest activity at pH 5.0-5.5 and $70-75^{\circ}C$. SaMTS, SaMTH, and SaMTSH fusion enzyme were active in soluble starch, which resulted in the production of trehalose.

• Bulletin of the Korean Chemical Society
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• v.1 no.3
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• pp.83-87
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• 1980

The Murrell-Fueno type of the intermolecular perturbation approach was applied to the acid-catalyzed hydrolysis of diformamide. The results show that: (1) the attack of a water molecule on the protonated carbonyl carbon is favored over that on the unprotonated carbonyl carbon; (2) the ${\sigma}$-approach model of water is preferred to the ${\pi}$-approach model; (3) the major contributing term to the total energy is the Coulomb energy, $E_q$, especially in the ${\sigma}$-approach, while the contribution of $E_{ct}$ (and $E_k$) increases moderately in the ${\pi}$-approach; (4) the reaction is a charge-controlled one, a hard-hard type in the language of the HSAB principle.