• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.377-381
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• 2002

Recently, interests to remove nitrogen in the nitritation process have increased because of its economical advantages, since it could be a short-cut process to save both oxygen for nitrification and carbon for denitrification compared to a typical nitrification. However, the kinetics related with the nitritation process has not yet been fully understood. Furthermore, many useful models which have been successfully used for wastewater treatment processes cannot be used to estimate effluent nitrite concentration for evaluating performance of the nitritation process, since the process rate equations and population of microorganisms for nitrogen removal in these models have been set up only for the condition of full nitrification. Therefore, the present study was conducted to estimate an effluent nitrite concentration in the nitritation process with a concept of enzymatic inhibition kinetics based on long-term laboratory experiments. Using a nonlinear least squares regression method, kinetic parameters were accurately determined. By setting up a process rate equation along with a mass balance equation of the nitrite-oxidizing step, an effluent nitrite concentration in the nitritation process was then successfully estimated.

• KSBB Journal
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• v.6 no.2
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• pp.157-166
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• 1991

The structural properties of cellulose are significantly changed with the progress of hydrolysis reaction. The effects of changes on such properties of cellulosic substrate as crystallinity, amicessibility of enzyme to the active site of cellulose surface, and particle size on the kinetics of enzymatic hydrolysis have been studied. Among those physical studies, the apparent surface active site of cellulose particle was found to have the most significant effect on the hydrolysis kinetics. Based on the experimental results, the adsorption affinity of enzyme and hydrolysis rate were mainly influenced by the surface roughness of cellulose particle. The extent of accesssible active site may be expressed as the change of particle diameter. The Langmuir isotherm was proposed in terms of enzyme activity to explain the actual action of enzyme protein.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.963-970
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• 2012

We review novel chemical kinetics proposed for quantitative description of fluctuations in reaction times and in the number of product molecules in a heterogeneous biological system, and discuss quantitative interpretation of randomness parameter data in enzymatic turnover times of ${\beta}$-galactosidase. We discuss generalization of renewal theory for description of chemical fluctuation in product level in a multistep biopolymer reaction occurring in a dynamically heterogeneous environment. New stochastic simulation results are presented for the chemical fluctuation of a dynamically heterogeneous reaction system, which clearly show the effects of the initial state distribution on the chemical fluctuation. Our stochastic simulation results are found to be in good agreement with predictions of the analytic results obtained from the generalized master equation.

• KSBB Journal
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• v.5 no.2
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• pp.133-139
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• 1990

A simple and convenient method was introduced to determine the kinetic parameters for various enzymatic reaction kinetics. The method based on integrated formular can be applied to the parameter estimations from a single experiment. A modified three-parameter model was applied for the parameter estimation in reversible reaction and the equilibrium substrate concentration could be also estimated. It is possible to identify the enzymatic reaction pattern by inspecting the parameter values and the square of the correlation coefficient.

• Journal of Pharmaceutical Investigation
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• v.27 no.2
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• pp.99-108
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• 1997

To evaluate the feasibility of mucosal delivery of thyrotropin releasing hormone (TRH) through various mucosae, enzymatic degradation and stabilization of TRH in the nasal, rectal and duodenal extracts of rabbits were studied. TRH in the extracts was assayed by HPLC and its degradation was found to follow apparent first-order kinetics. The residual concentrations of TRH in the mucosal extracts of nasal, rectal and duodenal segments after 24 hr of incubation were found to be $65.1({\pm}1.1),\;19.7({\pm}2.7)$ and 0%, and in the serosal extracts, $65.6({\pm}5.5),\;75.2({\pm}1.1)$ and $68.7({\pm}1.4)%$, respectively. This result suggests that there is a significant difference in the activity of TRH-degrading enzymes among the sites of administration. The inhibition of TRH degradation in the mucosa extracts was kinetically investigated using various additives such as thimerosal, benzalkonium chloride, disodium edetate, ${\sigma}-phenanthroline$, dithiothreitol and dithioerythritol, and $IC_{50}$ values of inhibitors were calculated. The results obtained showed that thimerosal (0.5 mM) and benzalkonium chloride (0.141 mM) protected TRH from the enzymatic degradation in all the mucosa extracts more than 95% after 24 hr of incubation.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1986.12a
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• pp.523.2-523
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• 1986

The hydrolysis of olive oil was attempted with immobilized C. rugosa lipase in the reverse phase solvent system. (i.e. immobilized wet particles is dispersed in continuous phase olive oil or organic solvents containing olive oil). Sephadex LH-20 and LH-60 were used as the supports that can be used in organic solvents. The water content of wet particles of sephadex LH-20 and LH-60 were about 72% (w/w) and 85% (w/w), respectively Both swollen gels with 0.05M buffers adsorbed about 18% of lipase dissolved. They were easily dispersed in liquid olive oil or in organic solvents. The effects of organic solvents on the stability and catalytic activity of the lipase have been examined. The results revealed that isooctane is superior to the other solvents examined for enzymatic fat spliting in reverse phase system. Kinetics of enzymatic hydrolys of olive oil by immobilized lipase has been investigated in a batch reactor. Effects of pH and temperature on the lipase were studied. The substrate concentration was influenced positively on the thermal stability.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.773-777
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• 2003

The color of Congo red hinders the spectrometric measurements of a concentration of hydrogen peroxide and enzyme activity (Horseradish peroxidase; HRP) during enzymatic decoloring of Congo red. In this study, a method was developed to measure peroxidase activity and hydrogen peroxide concentration in the presence of Congo red. The oxidation product of HRP/hydrogen peroxide and ABTS(2,2'-azino-bis-(3-ethylbenzotriazoline-6-sulfonic acid)) formed a dark green color. The spectrum of this product showed absorption bands at 420 nm and 734 nm. When compared with the Congo red spectrum, the absorption at 734 nm of this product did not overlap with Congo red, thus making the hydrogen peroxide measurement possible even in the presence of Congo red. Kinetic study of decoloring of Congo red performed by this method showed that the decoloring reaction followed the Michaelis-Menten kinetics. Pulse feeding of hydrogen peroxide, upon depletion, significantly increased the decoloring of Congo red. This result shows that this newly developed technique can monitor, predict, and improve the enzymatic decoloring process.

• Journal of Microbiology and Biotechnology
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• v.16 no.9
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• pp.1355-1361
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• 2006

The simultaneous saccharification and fermentation (SSF) process consists of concurrent enzymatic saccharification and fermentation. In the present cybernetic model, the saccharification process, which is based on the modified Michaelis-Menten kinetics and enzyme inhibition kinetics, was combined with the fermentation process, which is based on the Monod equation. The cybernetic modeling approach postulates that cells adapt to utilize the limited resources available to them in an optimal way. The cybernetic modeling was suitable for describing sequential growth on multiple substrates by Brettanomyces custersii, which is a glucose- and cellobiose-fermenting yeast. The proposed model was able to elucidate the SSF process in a systematic manner, and the performance was verified by previously published data.

• Molecules and Cells
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• v.39 no.1
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• pp.26-30
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• 2016

Peroxiredoxins are ubiquitous thiol proteins that catalyse the breakdown of peroxides and regulate redox activity in the cell. Kinetic analysis of their reactions is required in order to identify substrate preferences, to understand how molecular structure affects activity and to establish their physiological functions. Various approaches can be taken, including the measurement of rates of individual steps in the reaction pathway by stopped flow or competitive kinetics, classical enzymatic analysis and measurement of peroxidase activity. Each methodology has its strengths and they can often give complementary information. However, it is important to understand the experimental conditions of the assay so as to interpret correctly what parameter is being measured. This brief review discusses different kinetic approaches and the information that can be obtained from them.

• Journal of Microbiology and Biotechnology
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• v.27 no.2
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• pp.297-305
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• 2017

The use of peroxidase in the nitration of phenols is gaining interest as compared with traditional chemical reactions. We investigated the kinetic characteristics of phenol nitration catalyzed by horseradish peroxidase (HRP) in an aqueous-organic biphasic system using n-butanol as the organic solvent and ${NO_2}^-$ and $H_2O_2$ as substrates. The reaction rate was mainly controlled by the reaction kinetics in the aqueous phase when appropriate agitation was used to enhance mass transfer in the biphasic system. The initial velocity of the reaction increased with increasing HRP concentration. Additionally, an increase in the substrate concentrations of phenol (0-2 mM in organic phase) or $H_2O_2$ (0-0.1 mM in aqueous phase) enhanced the nitration efficiency catalyzed by HRP. In contrast, high concentrations of organic solvent decreased the kinetic parameter $V_{max}/K_m$. No inhibition of enzyme activity was observed when the concentrations of phenol and $H_2O_2$ were at or below 10 mM and 0.1 mM, respectively. On the basis of the peroxidase catalytic mechanism, a double-substrate ping-pong kinetic model was established. The kinetic parameters were ${K_m}^{H_2O_2}=1.09mM$, ${K_m}^{PhOH}=9.45mM$, and $V_{max}=0.196mM/min$. The proposed model was well fit to the data obtained from additional independent experiments under the suggested optimal synthesis conditions. The kinetic model developed in this paper lays a foundation for further comprehensive study of enzymatic nitration kinetics.