• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1221-1228
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• 2005

Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.332-336
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• 2010

Ionic liquid immobilized on mesoporous amorphous silica was prepared from the coupling of 1-(triethoxysilylpropyl)-3-n-alkyl-imidzolium halides with tetraethyl orthosilicate(TEOS) through template-free condensation under strong acidic conditions. The immobilized 1-n-butyl-3-methyl imidazolium bromide ionic liquid on amorphous silica(BMImBr-AS) was proved to be an effective heterogeneous catalyst for the synthesis of dimethyl carbonate(DMC) from transesterification of ethylene carbonate(EC) with methanol. High temperature, high carbon dioxide pressure and long reaction time were favorable for the reactivity of BMImBr-AS. Kinetic studies based on two step reactions revealed that the proposed reaction model fitted well the experimental data. The apparent activation energy was estimated to be 67.4 kJ/mol.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.432-437
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• 1999

Pyrolysis of polyethylene was carried out in the stainless steel reactor of internal volume of $10cm^3$. Pyrolysis reactions were performed at temperature $390{\sim}450^{\circ}C$ and the pyrolysis products were collected separately as reaction products and gas products. The molecular weight distributions(MWDs) of each product were determined by HPLC-GPC and GC analysis. Distribution balance equation for MWDs of random and specific products were proposed to account for initiation-termination and propagation-depropagation, such as hydrogen abstraction, chain cleavage, coupling of polymer and radical. A separate chain-end scission process produces low molecular weight noncondensable gases(C1 through C5) of average molecular weight 38. Activation energies of the random-chain scission and chain-end scission rate parameters, respectively, were determined to be 35, 17 kcal/mole.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.208-209
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• 2011

In this work, we developed self-assembled monolayers (SAMs) of alkanethiols on gold that can release amine groups, when an electrical potential was applied to the gold. The strategy was based on the introduction of the electroactive carbamate group, which underwent the two-electron oxidation with simultaneous release of the amine molecules, to alkanethiols. The synthesis of the designed thiol compounds was achieved by coupling isocyanate-containing compound with hydroquinone. The electroactive thiols were mixed with hydroxyl-containing alkanethiol [$HS(CH_2)_{11}OH$] to form mixed monolayers, and cyclic votammetry was used for the characterization of the release. The mixed SAMs showed a first oxidation peak at +540 mV (versus Ag/AgCl reference electrode), demonstrating irreversible conversion from carbamate to hydroqinone with simultaneous release of the amine groups. The second and third cycles showed typical reversible redox reaction of hydroquinone and quione: the oxidation and reduction occurred at +290 mV and -110 mV, respectively. The measurement of ToF-SIMS further indicates that electrochemical-assisted chemical reaction successfully released amine groups. This new SAM-based electrochemistry would be applicable for direct release of biologically active molecules that contain amine groups.

• Clean Technology
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• v.17 no.4
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• pp.325-328
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• 2011

Atom-efficient preparation of 9, 9'-bis[4-(2'-hydroxy-3'-acryloyloxypropoxy) phenyl]fluorene (3), the extensively used building block for fluorene-containing acrylic epoxy polymers has been described. The epoxide ring opening esterification of 9, 9-bis[4-(glycidyloxy)phenyl]fluorene (1) with acrylic acid was catalyzed by some onium salts such as quaternary ammonium and phosphonium salts. While the coupling reactions depend greatly on the kind of the onium salts, the reaction of 9, 9-bis[4-(glycidyloxy)phenyl]fluorene (1) with acrylic acid proceed most efficiently in the presence of a catalytic amount of tetrabutylphosphonium bromide at $110^{\circ}C$ with 90% yield. This reaction is a cleaner reaction that minimizes the use of reactants and the production of chemical wastes.

• The Korean Journal of Pesticide Science
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• v.8 no.3
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• pp.168-174
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• 2004

In a course of the process for a lead optimization of 2-imino-l,3-thiazolines 1 which show a selective in vivo antifungal activity against rice blast, new compounds 2 in which C-5 was substituted by methyl group of the lead compound were synthesized and tested for the biological activity. Bromination of $\beta$-keto ester 7 followed by the reaction with thiourea and hydrolysis gave 2-imino-5-methyl-l,3-thiazoline carboxylic acid 3. Coupling reactions of 3 with aniline derivatives afforded 17 kinds of the corresponding 2-imino-5-methyl-l,3-thiazoline carboxanilides 2. Their in vivo antifungal activity against rice blast was weaker than that of 1, indicating that the in vivo antifungal activity of 2-imino-l,3-thiazolines was affected by the substituent at C-5. These results would be an important data for the molecular design in the lead optimization process of this series.

• International Journal of Automotive Technology
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• v.7 no.1
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• pp.1-7
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• 2006

The ignition delay of a dual fuel system has been numerically investigated by adopting a constant volume chamber as a model problem simulating diesel engine relevant conditions. A detailed chemical kinetic mechanism, consisting of 28 species and 135 elementary reactions, of dimethyl ether (DME) with methane ($CH_{4}$) sub-mechanism has been used in conjunction with the multi-dimensional reactive flow KIVA-3V code to simulate the autoignition process. The start of ignition was defined as the moment when the maximum temperature in the combustion vessel reached to 1900 K with which a best agreement with existing experiment was achieved. Ignition delays of liquid DME injected into air at various high pressures and temperatures compared well with the existing experimental results in a combustion bomb. When a small quantity of liquid DME was injected into premixtures of $CH_{4}$/air, the ignition delay times of the dual fuel system are longer than that observed with DME only, especially at higher initial temperatures. The variation in the ignition delay between DME only and dual fuel case tend to be constant for lower initial temperatures. It was also found that the predicted values of the ignition delay in dual fuel operation are dependent on the concentration of the gaseous $CH_{4}$ in the chamber charge and less dependent on the injected mass of DME. Temperature and equivalence ratio contours of the combustion process showed that the ignition commonly starts in the boundary at which near stoichiometric mixtures could exists. Parametric studies are also conducted to show the effect of additive such as hydrogen peroxide in the ignition delay. Apart from accurate predictions of ignition delay, the coupling between multi-dimensional flow and multi-step chemistry is essential to reveal detailed features of the ignition process.

• Biomolecules & Therapeutics
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• v.25 no.2
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• pp.171-176
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• 2017

Streptomyces avermitilis produces clinically useful drugs such as avermectins and oligomycins. Its genome contains approximately 33 cytochrome P450 genes and they seem to play important roles in the biosynthesis of many secondary metabolites. The SAV_7130 gene from S. avermitilis encodes CYP158A3. The amino acid sequence of this enzyme has high similarity with that of CYP158A2, a biflaviolin synthase from S. coelicolor A3(2). Recombinant S. avermitilis CYP158A3 was heterologously expressed and purified. It exhibited the typical P450 Soret peak at 447 nm in the reduced CO-bound form. Type I binding spectral changes were observed when CYP158A3 was titrated with myristic acid; however, no oxidative product was formed. An analog of flaviolin, 2-hydroxynaphthoquinone (2-OH NQ) displayed similar type I binding upon titration with purified CYP158A3. It underwent an enzymatic reaction forming dimerized product. A homology model of CYP158A3 was superimposed with the structure of CYP158A2, and the majority of structural elements aligned. These results suggest that CYP158A3 might be an orthologue of biflaviolin synthase, catalyzing C-C coupling reactions during pigment biosynthesis in S. avermitilis.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.711-717
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• 2011

Two dimensional simulation results of a capacitively coupled oxygen plasma in a cylindrical reactor geometry are presented. Detailed electron impact reaction rates, which strongly depend on electron energy, are computed from collision cross sections of electrons with $O_2$ and O. Through the coupling of a three moment plasma model with a neutral chemistry/transport model are predicted spatiotemporal distributions of both charged species (electron, $O_2{^+}$, $O^+$, $O_2{^-}$, and $O^-$) and neutral species including ground states ($O_2$ and O) and metastables, known to play important roles in oxygen plasma, such as $O_2(a^1{\Delta}_g)$, $O_2(b^1{{\Sigma}_g}^+)$, $O(^1D)$, and $O(^1S)$. The simulation results clearly verify the existence of a double layer near sheath boundaries in the electronegative plasma.

• Journal of Microbiology and Biotechnology
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• v.31 no.1
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• pp.43-50
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• 2021

A newly cloned 4-α-glucanotransferase (αGT) from Deinococcus geothermalis and two typical bacterial αGTs from Thermus scotoductus and Escherichia coli (MalQ) were investigated. Among 4 types of catalysis, the cyclization activity of αGTs that produces cycloamylose (CA), a valuable carbohydrate making inclusion complexes, was intensively studied. The new αGT, DgαGT, showed close protein sequence to the αGT from T. scotoductus (TsαGT). MalQ was clearly separated from the other two αGTs in the phylogenetic and the conserved regions analyses. The reaction velocities of disproportionation, cyclization, coupling, and hydrolysis of three αGTs were determined. Intriguingly, MalQ exhibited more than 100-fold lower cyclization activity than the others. To lesser extent, the disproportionation activity of MalQ was relatively low. DgαGT and TsαGT showed similar kinetics results, but TsαGT had nearly 10-fold lower hydrolysis activity than DgαGT. Due to the very low cyclizing activity of MalQ, DgαGT and TsαGT were selected for further analyses. When amylose was treated with DgαGT or TsαGT, CA with a broad DP range was generated immediately. The DP distribution of CA had a bimodal shape (DP 7 and 27 as peaks) for the both enzymes, but larger DPs of CA quickly decreased in the DgαGT. Cyclomaltopentaose, a rare cyclic sugar, was produced at early reaction stage and accumulated as the reactions went on in the both enzymes, but the increase was more profound in the TsαGT. Taken together, we clearly demonstrated the catalytic differences between αGT groups from thermophilic and pathogenic bacteria that and showed that αGTs play different roles depending on their lifestyle.