• Journal of Microbiology and Biotechnology
• /
• v.13 no.5
• /
• pp.717-724
• /
• 2003

A newly isolated Citrobacter sp. Y19 catalyzes the CO-dependent $H_2$ production (biological water-gas shift reaction) by the actions of CO dehydrogenase (CODH) and hydrogenase. Y 19 requires $O_2$ for fast growth, but its $H_2$ production activity is significantly inhibited by $O_2$. In the present study, the effect of $O_2$ on the activities of CODH ard hydrogenase was investigated quantitatively in both whole cells and broken cells, based on CO-dependent or methyl viologen (MV)-dependent $H_2$ production in addition to CO-dependent MV reduction. In crude cell extracts, CODH activity was mostly found in the soluble fraction. Inactivation of CODH and hydrogenase activities by $O_2$ followed the first-order decay kinetics, and the dependence of the rate constants on $O_2$ partial pressure could be expressed by the Michaelis-Menten equation. In whole cells, the maximum deactivation rate constants ($k_{d,max}$ of hydrogenase and CODH were quite similar: $0.07{\pm}0.03 min^{-1}\;and\;0.10{\pm}0.04 min^{-1}$, respectively. However, the first-order rate constant ($k_{d,max}/K_s$) of CODH ($0.25\;min^{-1}\;atm^{-1}$) at low $O_2$ partial pressures was about 3-fold higher than that of the hydrogenase, since the half-saturation constant ($K_s$) of CODH was about half of that of hydrogenase. In broken cells, both enzymes became significantly more sensitive to $O_2$ compared to the unbroken cells, while $k_{d,max}/K_s$ increased 37-fold for hydrogenase and 6.7-fold for CODH. When whole cells were incubated under anaerobic conditions after being exposed to air for 1 h, hydrogenase activity was recovered more than 90% in 2 h suggesting that the deactivation of hydrogenase by $O_2$ was reversible. On the contrary, CODH activity was not recovered once deactivated by $O_2$ and the only way to recover the activity was to synthesize new CODH. This study indicates that $O_2$ sensitivity of $H_2$ production activity of Citrobacter sp. Y19 is an important drawback as in other $H_2-producing$ bactria.

• Polymer(Korea)
• /
• v.34 no.1
• /
• pp.32-37
• /
• 2010

Photo-alignment property of groove patterned surface prepared from blend of poly (vinyl cinnamate) (PVCi) and oligomeric dicinnamate was investigated for the application for alignment layer of liquid crystal display. The study of the photoreaction kinetics using UV-vis spectrum with the irradiation time showed that the reaction rate of oligomeric cinnamate was enhanced compared to that of PVCi. Blend where PVCi was main component showed a slight improvement on the photoreaction rate. It was unable to obtain groove patterned surface only using oligomeric cinnamate itself owing to the high crystalline character. However, blending of PVCi made it possible to obtain clear surface pattern. Molecular orientation could be confirmed from the polar plot data. It can be suggested that blend of oligomeric cinnamate and polymeric cinnamate is promising material for the photoalignment layer.

• Journal of the Korean Chemical Society
• /
• v.23 no.4
• /
• pp.248-258
• /
• 1979

Glucose 6-phosphate dehydrogenase of Leuconostoc mesenteroides which was purifid by an affinity chromatography was studied on the characterization, kinetics and chemical modification. The apparent molecular weight of the enzyme was 112,000 by the gel filtration method of Sephadex G-200 column. The optimum temperature of $NAD^+$-linked reation was 50$^{circ}C$ and the activation energy and the heat of inactivation were 8.36 kcal/mole and -58.2kcal/mole, respectively. The steady state kinetic study showed KG6P, Kemp, and CX KNADP to be 76.9 PM, 7.46${\mu}M$ and 7.14 ${\mu}M$, respectively, and KGGP, KNAD,and aKNm to be 53.7${\mu}M$, 115.2${\mu}M$ and 702.2${\mu}M$ for the $NAD^+$-linked reaction at pH 7.8, optimum pH. The pH dependent kinetic constants suggested that the two ionizing groups whose pKa is 7.2 .and pKb is 9.0-9.6 were involved in the enzyme-substrate interaction. Evidence by photooxidation and carboxymethylation of the enzyme suggested that the imidazole group of histidine with pKa group may participate in the catalytic site.

• Journal of Life Science
• /
• v.19 no.9
• /
• pp.1299-1303
• /
• 2009

The purpose of this study was to analyse the gait characteristics of stroke patients walking on a Zebris system, through quantitative three-dimensional biomechanical analysis. They underwent a continuous rehabilitation training program (RTP). A comparison was made between 3 month and 6 month RTP participants. Their ages were between 60 and 65. The data were analyzed by t-test. The result of comparative analysis of the two groups can be summarized as below. Temporal-spatial data, sagittal plane angular kinematics data, and peak ground reaction force and max pressure data showed that there were no significant differences between the 3 month RTP group and the 6month RTP group (Table 2, Table3, Table 4). It can be suggested that patients with hemiplegia after stroke can improve their walking function through continuous RTP participation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.9
• /
• pp.1663-1670
• /
• 2006

Single crystal Fe thin films were grown directly onto n-Si(111) substrates by pulsed electrodeposition. Cyclic Voltammogram(CV) indicated that the $Fe^{2+}/n-Si(111)$ interface shows a good diode behavior by forming a Schottky barrier. From Mott-Schottky (MS) relation, it is found that the flat-band potential of n-Si(111) substrate and equilibrium redox potential of $Fet^{2+}$ ions are -0.526V and -0.316V, respectively. The nucleation and growth kinetics at the initial reaction stages of Fe/n-Si(111) substraste was studied by current transients. Current transients measurements have indicated that the deposition process starts via instantaneous nucleation and 3D diffusion limited growth. After the more deposition, the deposition flux of Fe ions was saturated with increase of deposition time. from the as-deposited sample obtained using the potential pulse of 1.4V and 300Hz, it is found that Fe nuclei grows to three dimensional(3D) islands with the average size of about 100nm in early deposition stages. As the deposition time increases, the sizes of Fe nuclei increases progressively and by a coalescence of the nuclei, a continuous Fe films grow on the Si surface. In this case, the Fe films show a highly oriented columnar structure and x-ray diffraction patterns reveal that the phase ${\alpha}-Fe$ grows on the n-Si(111) substrates.

• Proceedings of KOSOMES biannual meeting
• /
• 2007.11a
• /
• pp.97-102
• /
• 2007

The piggery wastewater is the major source of the water pollution problem in the rural area. The treatment alternatives for piggery wastewater are limited by the characteristics of both high organic and nitrogen(N) content. In order to investigate an efficient N removal system, the thermophilic aerobic digestion process was examined. The experiment was investigated organic and nitrogen removal efficiency at various HRTs and air supply volume. The results of semi-continuous experiment indicated that a higher removal of the soluble portion of COD was achieved with the longer HRTs. However, the inert portion of COD in piggery wastewater was not much changed by thermophilic aerobic digestion. In addition, with the higher HRT of 3 days, up to 79% of NH4-N removal efficiency was achieved. Lower the HRTs, a decrease of NH4-N removal was founds. The gas samples from the lab reactor were analyzed along with the N content in influent and effluent. The N2O formation in our system indicates a novel aerobic deammonification process occurred during the thermophilic aerobic digestion. Both N02 and N03 were not presented in the effluent of thermophilic aerobic digester. With the HRT of 3 days, 36.4% of influent N(or 57.5% removal N) was aerobically converted to N2O gas. The ammonium conversion to N2O gas significantly decrease to 4.5% at low HRT of .05 day..

• Applied Chemistry for Engineering
• /
• v.31 no.4
• /
• pp.443-451
• /
• 2020

In this study, the physico-chemical properties and pyrolysis kinetics of livestock mature solid fuel were investigated to know its feasibility as a fuel. Ultimate and proximate analysis results showed that livestock mature solid fuel has high contents of volatile matter (64.94%), carbon (44.35%), and hydrogen (5.54%). The low heating value of livestock mature solid fuel (3880 kcal/kg) was also higher than the standard requirement of solid fuel (3000 kcal/kg). Thermogravimetic analysis results indicated that livestock mature solid fuel has three decomposition temperature regions. The first temperature zone (130~330 ℃) was consisted with the vaporization of extracts and the decomposition of hemicellulose and cellulose. The second (330~480 ℃) and third (550~800 ℃) temperature regions were derived from the decomposition of lignin and additional decomposition of carbonaceous materials, respectively. The activation energy derived from model free kinetic analysis results including Friedman, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods for the pyrolysis of livestock mature solid fuel was in the range of 173.98 to 525.79 kJ/mol with a conversion rate of 0.1 to 0.9. In particular, the activation energy increased largely at the higher conversion than 0.6. The kinetic analysis using a curve-fitting method suggested that livestock mature solid fuel was decomposed via a multi-step reaction which can be divided into five decomposition steps.

• Journal of Korean Society of Water and Wastewater
• /
• v.24 no.4
• /
• pp.433-442
• /
• 2010

BER at different packing ratios of bio-ring media(BRM) was tested to investigate the effect of varying hydraulic retention time (HRT) and current density on the nitrate removal and current efficiency. In the preliminary batch mode experiment of BERs, current density was applied at 2.0 A/$m^2$, 4.0 A/$m^2$, 4.8 A/$m^2$, which correspond to the designation of reactor #1, #2, #3, respectively. The reactor #2 showed a highest nitrate removal rate of 162.0 mg $NO_3{^-}$-N/L/d, and the kinetics of nitrate removal rate was defined as the Zero order reaction. In the primary experiment of BERs, four BERs packed with BRM were operated in varying HRT and current, and the packing ratios of reactor #1, #2, #3 and #4 were 0%, 8%, 16%, 24%. respectively. This results of the experiments indicated that the nitrate removal rate and current efficiency were increased significantly cause of growing of autotrophic denitrification microorganisms on the surface of cathode and media by increasing of the current density and decreasing of HRT. However, The decreasing of nitrate removal rate and current efficiencies were observed in the condition of HRT of 5.25 hr and 4.8 A/$m^2$ of current density. With more increasing current density and decreasing of HRT, the hydrogen inhibition occurred at the surface of cathode. Moreover, nitrate removal rate by autotrophic denitrification microorganisms attached on the media surface was observed to be limited by no longer increasing dissolved hydrogen concentration of each reactor. In conclusion, the highest nitrate nitrogen removal and current efficiency could be achieved when the BER was operated at the conditions of 7 hr HRT, current density of 4.0 A/$m^2$, and 16% packing ratio. And it was found that the amount of nitrate removal by microorganisms attached on the surface of cathode and media (BRM) was 178.2 mg/L and 52.2 mg/L respectively. and the amount of nitrate removal per MLVSS was 0.435 g $NO_3{^-}$-N/g $MLVSS{\cdot}d$ and 0.336 $NO_3{^-}$-N/g $MLVSS{\cdot}d$.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.10 no.3
• /
• pp.127-136
• /
• 1990

In this paper, the experimental study was carried out for the removal of olive oil in wastewater by the use of Biological Fluidized Bed(BFB) with the reticulated polypropylene sheets as media. The nonbiodegradable olive oil, one of the animal and vegitable oil, was used bacause of the relative simplicity of constitution. Biological degraciability and removal characteristics of emulsified olive oil were studied by batch and continuous experiments respectively. From the results of batch experiments, it was observed that the emulsified olive oli used in BFB reactor was absorbed by media and sludge in about 12 hours, and degradation of the absorbed olive oli was mostly completed for 24 hours. The functional relationship of Michaelis-Menten's Enzyme reaction equation exists between oil concentration and maximum specific rate of olive oil. From the continuous experiments for the removal of olive oil using BFB reactor, it was proved that the substrate removal rate coefficient $k=0.004d^{-1}$, which is the first order kinetics. It was apperared that oxygen utlization coefficients for synthesis(a') and endogeneous respiration(b') of microorganisms in the reactor are respectively 0.85mg $O_2/mg$ $COD_{cr}$ and 0.011mg $O_2/mg$ BVS. day.

• Asian-Australasian Journal of Animal Sciences
• /
• v.33 no.1
• /
• pp.127-131
• /
• 2020

Objective: This study was conducted to determine catalytic properties of wheat phytase with exopolyphosphatase activity toward medium-chain and long-chain inorganic polyphosphate (polyP) substrates for comparative purpose. Methods: Exopolyphosphatase assay of wheat phytase toward polyP75 (medium-chain polyP with average 75 phosphate residues) and polyP1150 (long-chain polyP with average 1150 phosphate residues) was performed at pH 5.2 and pH 7.5. Its activity toward these substrates was investigated in the presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or ethylenediaminetetraacetic acid (EDTA). Michaelis constant (K_m) and maximum reaction velocity (V_max) were determined from Lineweaver-Burk plot with polyP75 or polyP1150. Monophosphate esterase activity toward p-nitrophenyl phosphate (pNPP) was assayed in the presence of polyP75 or polyP1150. Results: Wheat phytase dephosphorylated polyP75 and polyP1150 at pH 7.5 more effectively than that at pH 5.2. Its exopolyphosphatase activity toward polyP75 at pH 5.2 was 1.4-fold higher than that toward polyP1150 whereas its activity toward polyP75 at pH 7.5 was 1.4-fold lower than that toward polyP1150. Regarding enzyme kinetics, K_m for polyP75 was 1.4-fold lower than that for polyP1150 while V_max for polyP1150 was 2-fold higher than that for polyP75. The presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or EDTA (1 or 5 mM) exhibited no inhibitory effect on its activity toward polyP75. Its activity toward polyP1150 was inhibited by 1 mM of Ni²⁺ or Co²⁺ and 5 mM of Ni²⁺, Co²⁺, or Mg²⁺. Ni²⁺ inhibited its activity toward polyP1150 the most strongly among tested additives. Both polyP75 and polyP1150 inhibited the monophosphate esterase activity of wheat phytase toward pNPP in a dose-dependent manner. Conclusion: Wheat phytase with an unexpected exopolyphosphatase activity has potential as a therapeutic tool and a next-generational feed additive for controlling long-chain polyP-induced inappropriate inflammation from Campylobacter jejuni and Salmonella typhimurium infection in public health and animal husbandry.