• BMB Reports
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• v.44 no.2
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• pp.102-106
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• 2011

Thermodynamic stability and refolding kinetics of firefly luciferase and three representative mutants with depletion of negative charge on a flexible loop via substitution of Glu by Arg (ER mutant) or Lys (EK mutant) as well as insertion of another Arg in ER mutants (ERR mutant) was investigated. According to thermodynamic studies, structural stability of ERR and ER mutants are enhanced compared to WT protein, whereas, these mutants become prone to aggregation at higher temperatures. Accordingly, it was concluded that enhanced structural stability of mutants depends on more compactness of folded state, whereas aggregation at higher temperatures in mutants is due to weakening of intermolecular repulsive electrostatic interactions and increase of intermolecular hydrophobic interactions. Kinetic results indicate that early events of protein folding are accelerated in mutants.

• 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.

• Korea-Australia Rheology Journal
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• v.17 no.1
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• pp.21-25
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• 2005

Rheological properties and crystallization kinetics of the polypropylene (PP) block copolymer and recycled PP block copolymer were studied by advanced rheometric expansion system (ARES), differential scanning calorimetry (DSC), and optical microscopy. In the study of the dynamic rheology, it is observed that the storage modulus and loss modulus for the PP block copolymer and recycled PP block copolymer did not change with frequency. In the study of the effect of the repeated extrusion on the crystallization rate, half crystallization time of the PP samples was increased with the number of repeated extrusion in isothermal crystallization temperature ($T_c$). From the isothermal crystallization kinetics study, the crystallization rate was decreased with the increase of the number of repeated extrusion. Also, from the result of Avrami plot, the overall crystallization rate constant (K) was decreased with the increase of the number of the repeated extrusion. From the study of the optical microscopy, the size of the spherulite of the PP samples did not change significantly with the number of repeated extrusion. However, it was clearly observed that the number of the spherulite growth sites was decreased with the number of repeated extrusion. From the results of the crystallization rate, isothermal crystallization kinetics, Avrami plots, and optical microscopy, it is suggested that the crystallization rate of the PP block copolymer is decreased with the increase of the number of repeated extrusion.

• 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.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.382-390
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• 2015

Poly(methyl methacrylate) (PMMA) supports and amine additives were investigated to adsorb $CO_2$. PMMA supports were fabricated by using different ratio of pore forming agents (porogen) to control the BET specific surface area, pore volume and distribution. Toluene and xylene are used for porogens. Supported amine sorbents were prepared by wet impregnation of tetraethylenepentamine (TEPA) on PMMA supports. So we could identify the effect of the pore structure of supports and the quantity of impregnated TEPA on the adsorption capacity. The increased amount of toluene as pore foaming agent resulted in the decreased average pore diameter and the increased BET surface area. Polymer supports with huge different pore distribution could be fabricated by controlling the ratio of porogen. After impregnation, the support with micropore structure is supposed the pore blocking and filling effect so that it has low $CO_2$ capacity and kinetics due to the difficulty of diffusing. Macropore structure indicates fast adsorption capacity and low influence of amine loading. In case of support with mesopore, it has high performance of adsorption capacity and kinetics. So high surface area and meso-/macro- pore structure is suitable for $CO_2$ capture.

• Korean Journal of Environmental Agriculture
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• v.26 no.1
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• pp.55-61
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• 2007

Metolachlor may pose a threat to surface and ground water qualities due to its high solubility in water, Zerovalent iron (ZVI) releases $e^-$ which can degrade the organochlorinated compounds. The objective of this research was to evaluate the kinetics of metolachlor degradation as affected by ZVI sources [Peerless unannealed (PU) and Peerless annealed (PA)] and ZVI levels (1 and 5%) under batch conditions at different metolachlor concentrations (200 and 1000 mg/l) and temperatures (15, 25, and $35^{\circ}C$). The effectiveness of ZVI on metolachlor degradation was assessed by characterizing the dechlorinated metolachlor byproduct molecules. Metolachlor degradation by ZVI followed the first-ordered kinetics with a higher rate constant at higher level of ZVI treatment. At 5% (w/v) of PU and PA treatment, the half-lives of metolachlor degradation were 9.93 and 6.51 h and all of the initial metolachlor were degraded in 72 and 48 h, respectively. Rate constants (k) of metolachlor degradation were higher at the lower initial metolachlor concentration. The metolachlor degradation by ZVI was temperature dependent showing that the rate constant (k) at 15, 25, and $35^{\circ}C$ were 0.0805, 0.1017, and 0.3116 /h, respectively. The ZVI-mediated metolachlor degradation yielded two byproduct molecules identified as dechlorinated metolachlor $(C_{13}H_{18}NO)$ and dechlorinated-dealkylated metolachlor $(C_{12}H_{17}NO)$. The PA ZVI was more effective than PU ZVI in metolachlor degradation.

• Environmental Engineering Research
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• v.9 no.5
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• pp.238-247
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• 2004

The objective of this study was to develop kinetic model for the MBR and investigate kinetic characteristics of the gravitational flow transverse direction MBR system. Kinetic model was derived by mass balance of substratc and biomass combined with empirical membranc filtration rerm for the MBR. To find kinctic values, permeale flux and COD removal were analyzed through the laboratory, MBR operation as different solids retention times. Permeate flux was ranged 2.5-5.0 LMH (L/m$^2$/hr) as sludge characteristics in each run. Although the soluble COD in the bioreactor was changed, the effluent COD was stable as average 99% removal rate during the experimental periods. Y$_g$ of this MBR system was higher than those of cross-flow MBR processes. The kinetics of this MBR showed that smaller k, larger b, and larger K$_s$ values than the conventional activated sludge process. These results indicated that substrate was used for cell maintenance rather than growth in this MBR system.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.251-259
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• 2023

Immobilizing microalgae cells in a hyphal matrix can simplify harvest while producing novel mycoalgae products with potential food, feed, biomaterial, and renewable energy applications; however, limited quantitative information to describe the process and its applicability under various conditions leads to difficulties in comparing across studies and scaling-up. Here, we demonstrate the immobilization of both active and heat-deactivated marine diatom Phaeodactylum tricornutum (UTEX 466) using different loadings of fungal pellets (Aspergillus sp.) and model the process through kinetics and equilibrium models. Active P. tricornutum cells were not required for the fungal-assisted immobilization process and the fungal isolate was able to immobilize more than its original mass of microalgae. The Freundlich isotherm model adequately described the equilibrium immobilization characteristics and indicated increased normalized algae immobilization (g algae removed/g fungi loaded) under low fungal pellet loadings. The kinetics of algae immobilization by the fungal pellets were found to be adequately modeled using both a pseudo-second order model and a model previously developed for fungal-assisted algae immobilization. These results provide new insights into the behavior and potential applications of fungal-assisted algae immobilization.

• Journal of Biomedical Engineering Research
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• v.4 no.1
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• pp.9-14
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• 1983

A new quantitative method was developed for separation of three interactive physiological factors (hepatic glucose balance, peripheral tissue's insulin resistivity, and insulin secretion rate) influencing glucose intolerance in diabetic mellitus using an equivalent circuit model and the intravenous glucose tolerance test (IVGTT) in six dogs and twenty two humans. The results show that the estimated model parameters of the above three factors are useful for evaluating different glucose-insulin kinetics in normal and diabetic subjects.

• 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.