• Journal of Microbiology and Biotechnology
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• v.4 no.3
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• pp.204-209
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• 1994

The synthesis of N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methylester (Z-APM), a precursor of aspartame, from N-(benzyloxycarbonyl)-L-aspartic acid (Z-Asp) and L-phenylalanine methylester hydrochlolide($L-PM\cdot HCI$) was investigated in a saturated-ethylacetate single phase system using immobilized thermolysin. Among the various supports tested, glyceryl-CPG was found to be most efficient for retaining enzyme activity. The enzyme immobilized onto glyceryl-CPG also showed the highest activity for Z-APM synthesis in saturated ethyl acetate. Z-APM conversion yield in saturated ethylacetate was half of that obtained in an ethyl acetate-buffer two-phase system under the same reaction conditions. However, as the mole ratio of $L-PM \cdot HCI$ to Z-Asp was increased to 4.0, the conversion yield reached 95 %. When continuous synthesis of Z-APM was canied out in a plug flow reactor (PFR) with 80 mM of L-PMㆍHCI and 20 mM of Z-Asp in saturated ethylacetate (pH 5.5), more than 95 % of Z-Asp was converted to Z-APM with a space velocity of 1.16 $hr^{-1} at 40^{\circ}C$. Although the operational stability in PFR was reduced rapidly, more than 80% of initial activity was maintained in CSTR even after a week of operation.

• Environmental Engineering Research
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• v.16 no.4
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• pp.231-236
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• 2011

Biological nitrogen removal, using a continuous flow packed-bed reactor (CPBR) in a consecutive nitrification and denitrification process, was evaluated. An apparent decline in the nitrification efficiency coincided with the steady increase in $NH_4{^+}$-N load. Sustained nitrification efficiency was found to be higher at longer empty bed contact times (EBCTs). The relationship between the rate of alkalinity consumption and $NH_4{^+}$-N utilization ratio followed zero-order reaction kinetics. The heterotrophic denitrification rate at a carbon-tonitrogen (C/N) ratio of >4 was found to be >74%. This rate was higher by a factor of 8.5 or 8.9 for $NO_3{^-}$-N/volatile solids (VS)/day or $NO_3{^-}-N/m^3$ ceramic media/day, respectively, relative to the rates measured at a C/N ratio of 1.1. Autotrophic denitrification efficiencies were 80-90%. It corresponds to an average denitrification rate of 0.96 kg $NO_3{^-}-N/m^3$ ceramic media/day and a relevant average denitrification rate of 0.28 g $NO_3{^-}$-N/g VS/day, were also obtained. Results presented here also constitute the usability of an innovative porous sulfur ceramic media. This enhanced the dissolution rate of elemental sulfur via a higher contact surface area.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.267-267
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• 2012

$TiO_2$-Ni inverse catalysts were prepared using atomic layer deposition (ALD) process and catalytic $CO_2$ reforming of methane (CRM) reaction over catalysts (either bare Ni or $TiO_2$ coated-Ni particles) were performed using a continuous flow reactor at $800^{\circ}C$. $TiO_2$-Ni inverse catalyst showed higher catalytic reactivity at initial stage of CRM reactions at $800^{\circ}C$ comparing to bare Ni catalysts. Moreover, catalytic activity of $TiO_2$/Ni catalyst was kept high during 13 hrs of the CRM reactions at $800^{\circ}C$, whereas deactivation of bare Ni surface was started within 1hr under same conditions. The results of surface analysis using SEM, XPS, and Raman showed that deposition of graphitic carbon was effectively suppressed in a presence of $TiO_2$ nanoparticles on Ni surface, thereby improving catalytic reactivity and stability of $TiO_2$/Ni catalytic systems. We suggest that utilizing decoration effect of metal catalyst with oxide nanoaprticles is of great potential to develop metal-based catalysts with high stability and reactivity.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.575-582
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• 1989

The effects of raw material feeding procedures and gelation temperatures on zeolite synthesis are investigated. Thus, the synthesis of zeolite 4A from sodium aluminate and sodium silicate solutions is chosen as a model reaction, for which equi-molar hydrogelation is performed with variation of feeding procedures and gelation temperatures. The formation of crystal nuclei, often being referred to as precursors, is induced under different conditions, the variation being examined by means of viscosity and water contents. The final products of zeolite 4A are evaluated by XRD, SEM morphology, particle size analysis and cation exchange capacity. Evidence shows that the viscosity of the initial products and their water contents are markedly influenced by the feeding methods of the reactant materials and by the gelation temperature. Further, it is found that the gelation at an elevated temperatures near 7$0^{\circ}C$ can be made possible through modification of mixing procedures. This provides convenient means of controlling the particle size of the final products. In this regard, a continuous flow-type mixing technique is proposed, which is demonstrated to be superior to the conventional batch-type mixings. The significance of this finding may lie in savings of equipment as well as energy costs, especialy on a large scale commercialization of zeolite production.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.681-697
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• 1994

The enzymatic hydrolysate of gelatin extracted from fish skin was fractionated and recycled through the membrane reactor according to the molecular weight for the purpose of using as functional material. In addition, the enzymatic hydrolysis conditions of gelatin, enzyme stability by membrane and mechanical shear, and effect on the long-term operational stability of the recycle membrane reactor were investigated. Using the pH-drop technique, Alcalase, pronase E and collagenase were identified as the most suitable enzymes for the hydrolysis of fish skin gelatin. The optimum hydrolysis conditions in the 1st-step membrane reactor(1st-SMR) by Alcalase were enzyme concentration 0.2mg/ml, substrate-to-enzyme ratio(S/E) 50(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the 2nd-SMR by pronase E were enzyme concentration 0.3mg/ml, S/E 33(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the case of 3rd-SMR, enzyme concentration 0.1mg/ml, S/E 100(w/w), $37^{\circ}C$, pH 7.5, reaction volume 600ml and flow rate 10ml/min. Decreased enzyme activities by mechanical shear and membrane were 30% and 15% in the 1st-SMR, were 14% and 5% in the 2nd-SMR, and 18% and 8% in the 3rd-SMR, respectively. Under the optimum conditions, the degree of hydrolysis in the 1st, 2nd and 3rd-SMR were 3.5%(Kjeldahl method, 87%), 3.1%(77%) and 2.7%(70%), respectively. The productivity of hydrolysate in the continuous three-step membrane reactor was 430mg per enzyme(mg) for 10 times of volume replacements.

• Journal of the Korean Vacuum Society
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• v.21 no.3
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• pp.178-184
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• 2012

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils were investigated as functions of additive gas flow rate and the cycling on/off modulation of $C_2H_2/SF_6$ flows. Even in the lowest $SF_6$ flow rate (5 sccm) in this work, the cycling on/off modulation injection of $SF_6$ flow for 2 minutes could give rise to the formation of nanosized carbon coils, whereas the continuous injection of $SF_6$ flow for 5 minutes could not give rise to the carbon coils formation. With increasing $SF_6$ flow rates from 5 to 30 sccm, the cycling on/off modulation injection of $SF_6$ flow confines the geometry for the carbon coils to the nanosized ones. Fluorine's role of $SF_6$ during the reaction was regarded as the main cause for the confinement of carbon coils geometries to the nano-sized ones.

• Journal of the Korean Chemical Society
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• v.34 no.5
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• pp.445-451
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• 1990

The catalytic ammoxidation of methylpyrazine into cyanopyrazine over a supported vanadium oxides catalyst on ${\gamma}$-alumina was studied in a continuous-flow fixed bed reactor. Various crystalline phases of vanadium oxides were obtained depending on reduction temperatures. And also the activities for the reaction of methylpyrazine into cyanopyrazine were affected by their major oxidation states of the corresponding crystalline phases. The 10${\%}$ vanadium oxides loaded ${\gamma}$-alumina catalyst, which was reduced at 600$^{\circ}C$ under the hydrogen flow for 2 hours, showed the highest activity and the highest selectivity on cyanopyrazine in the ammoxidation of methylpyrazine.Its major crystalline phase was V$_2$O$_3$ with the presence of V$_6$O$_{13}$ and V$_2$O$_4$(VO$_2$) together. And this coexistance seemed to enhance the activity.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1720-1726
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• 2014

(S)-Alanine Racemase Chiral Analogue ((S)-ARCA) was used as an efficient adsorbent for the selective separation of D-amino acids (D-AAs), which are industrially important as chiral building blocks for the synthesis of pharmaceutical intermediates. The organic phase, containing (S)-ARCA adsorbent and phase transfer reagents, such as ionic liquid type molecules (Tetraphenylphosphonium chloride (TPPC), Octyltriphenylphosponium bromide (OTPPBr)), were coated on the surfaces of mesoporous carbon supports. For the immobilization of chiral adsorbents, meso/macroporous monolithic carbon (MMC), having bimodal pore structures with high surface areas and pore volumes, were fabricated. The separation of chiral AAs by adsorption onto the heterogeneous (S)-ARCA was performed using a continuous flow type packed bed reactor system. The effects of loading amount of ARCA on the support, the molar ratio of AA to ARCA, flow rates, and the type of phase transfer reagent (PTR) on the isolation yields and the optical purity of product D-AAs were investigated. D-AAs were selectively combined to (S)-ARCA through imine formation reaction in an aqueous basic solution of racemic D/L-AA. The (S)-ARCA coated MMC support showed a high selectivity, up to 95 ee%, for the separation of D-type phenylalanine, serine and tryptophan from racemic mixtures. The ionic liquids TPPC and OTPPBr exhibited superior properties to those of the ionic surfactant Cetyltrimethyl ammonium bromide (CTAB), as a PTR, showing constant optical purities of 95 ee%, with high isolation yields for five repeated reuses. The unique separation properties in this heterogeneous adsorption system should provide for an expansion of the applications of porous materials for commercial processes.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.5
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• pp.424-430
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• 2005

The oral cavity is humid environment mainly due to the continuous salivary flow. The reaction of oral mucosa to fluid flow is important for homeostasis and pathogenesis. The objective of this study is the screening the change of gene expression after the application of fluid induced shear stress (FISS) on the gingival fibroblast using cDNA microarray assay. The immortalized human gingival fibroblasts were grown and FISS was applied using a cone viscometer at a rotational velocity of 40 rpm, respectively for periods of 2 and 4 hours. The synthesis of cDNA was done from the extracted total RNA and cDNA microarray assay was done subsequently. The genes that showed over 1.6 in the Cy3/Cy5 or the Cy5/Cy3 value were regarded as genes influenced significantly by the FISS application ion (/M/>0.7). The " RUNX-1" was increased its expression in 2 hours group and " RUN and SH3 domain containing 1" was increased its expression in 4 hours group. The "CC020415", "cyclin L1", "interferon regulatory factor1", "early growth response 1", "immediate early response 2", and "immediate early response 3" genes were increased their expression in 2 and 4 hours after FISS application. In conclusion, we could find many genes that were probably related to the FISS application. Interestingly, most of them were placed in similar molecular pathways and these findings improve the reliability of chip data and usefulness in overall screening. From this experiment, we could find many items for further study and it will make improvement in the understanding of intracellular events in response to FISS.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.295-304
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• 1994

$Mo-V-O/SnO_2$(VM/Sn) and $SnO_2/Mo-V-O$(Sn/VM) catalysts have been prepared and characterized by XRD, BET, SEM and TPD of ammonia. The catalytic reaction of acrolein oxidation with these catalysts, in a continuous-flow fixed-bed reactor, showed that they had higher conversion of acrolein and higher yield of acrylic acid than those of Mo-V-O itself. The origin of the observed synergy studied by TPD, TPR and TPO is explained by the cooperation of $SnO_2$ and Mo-V-O at their interfaces where electrons flow from Mo-V-O phase to $SnO_2$ and $SnO_2$ produces spill-over oxygens, which, by being transported onto the surface of Mo-V-O, reoxidize the partially reduced active sites.