scholarly journals Improvement of recovered activity and stability of the Aspergillus oryzae β-galactosidase immobilized on duolite A568 by combination of immobilization methods

2017 ◽  
Vol 23 (4) ◽  
pp. 495-506 ◽  
Author(s):  
Larissa Falleiros ◽  
Bruna Cabral ◽  
Janaína Fischer ◽  
Carla Guidini ◽  
Vicelma Cardoso ◽  
...  
Keyword(s):  
Activation Energy ◽  
Aspergillus Oryzae ◽  
Physical Adsorption ◽  
Cross Linking ◽  
Thermal Deactivation ◽  
Order Model ◽  
First Order ◽  
Immobilized Biocatalyst ◽  
The Stability ◽  
Kinetics Of

The immobilization and stabilization of Aspergillus oryzae ?-galactosidase on Duolite??A568 was achieved using a combination of physical adsorption, incubation step in buffer at pH 9.0 and cross-linking with glutaraldehyde and in this sequence promoted a 44% increase in enzymatic activity as compared with the biocatalyst obtained after a two-step immobilization process (adsorption and cross-linking). The stability of the biocatalyst obtained by three-step immobilization process (adsorption, incubation in buffer at pH 9.0 and cross-linking) was higher than that obtained by two-steps (adsorption and cross-linking) and for free enzyme in relation to pH, storage and reusability. The immobilized biocatalyst was characterized with respect to thermal stability in the range 55-65 ?C. The kinetics of thermal deactivation was well described by the first-order model, which resulted in the immobilized biocatalyst activation energy of thermal deactivation of 71.03 kcal/mol and 5.48 h half-life at 55.0 ?C.

scholarly journals Thermodynamics and kinetics of thermal deactivation of catalase Aspergillus niger

2020 ◽  
Vol 22 (2) ◽  
pp. 67-72
Author(s):  
Justyna Miłek
Keyword(s):  
Aspergillus Niger ◽  
Life Time ◽  
Economic Feasibility ◽  
Thermal Deactivation ◽  
Order Model ◽  
First Order ◽  
Thermodynamics And Kinetics ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Thermal Stability Of

AbstractThe thermal stability of enzyme-based biosensors is crucial in economic feasibility. In this study, thermal deactivation profiles of catalase Aspergillus niger were obtained at different temperatures in the range of 35°C to 70°C. It has been shown that the thermal deactivation of catalase Aspergillus niger follows the first-order model. The half-life time t1/2 of catalase Aspergillus niger at pH 7.0 and the temperature of 35°C and 70°C were 197 h and 1.3 h respectively. Additionally, t1/2 of catalase Aspergillus niger at the temperature of 5°C was calculated 58 months. Thermodynamic parameters the change in enthalpy ΔH*, the change in entropy ΔS* and the change Gibbs free energy ΔG* for the deactivation of catalase at different temperatures in the range of 35°C to 70°C were estimated. Catalase Aspergillus niger is predisposed to be used in biosensors by thermodynamics parameters obtained.

THE THERMAL DECOMPOSITION OF STYRENE–BUTADIENE POPCORN POLYMER

1950 ◽  
Vol 28b (1) ◽  
pp. 5-16
Author(s):  
C. A. Winkler ◽  
J. Halpern
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Linear Relation ◽  
Frequency Factor ◽  
Thermal Reaction ◽  
Cross Linking ◽  
First Order ◽  
Bond Scission ◽  
Styrene Butadiene ◽  
Kinetics Of

At temperatures of the order of 250 °C., popcorn polymer undergoes decomposition to soluble polymer. The reaction is catalyzed by peroxides present in the popcorn when the latter is formed. These peroxides may be removed by extracting the polymer with benzene. The kinetics of both the catalyzed and purely thermal solubilization reactions were investigated. The rates of both reactions are first order, the catalyzed degradation having a higher activation energy and a higher frequency factor. The rate of the thermal reaction decreases and its activation energy increases with increasing butadiene content of the polymer. A linear relation between the activation energy and the log of the frequency factor, for the decomposition of popcorn polymers of different butadiene contents, was observed. The results indicate that the rate of solubilization is determined by the activation energy of the bond scission process, and is independent of the degree of cross-linking of the polymer.

Study of Thermal Decomposition and Kinetics of Biomass/Swill-Cooked Dirty Oil Blends during Co-Pyrolysis

2011 ◽  
Vol 347-353 ◽  
pp. 2684-2687
Author(s):  
Yu Wang ◽  
Wen Chao Ma ◽  
Guan Yi Chen
Keyword(s):  
Activation Energy ◽  
Inert Atmosphere ◽  
Thermal Gravimetric ◽  
Kinetics Analysis ◽  
Order Model ◽  
First Order ◽  
Oil Blends ◽  
Thermal Gravimetric Analyzer ◽  
Kinetics Of ◽  
Synergistic Relationship

This paper studied the co-pyrolysis behavior of crop straw and swill-cooked dirty oil (≈ 2:1 ratio by weight) at 10, 30, 50K/min, in dynamic thermal gravimetric analyzer (TGA) under inert atmosphere, from 303K to 973K. The kinetic parameters were calculated using the method of Ozawa-Flynn-Wall, and mechanism was hypothesized as first-order model. The results showed that the dirty oil led degradation temperatures to slide towards higher slightly, meanwhile broadened the temperature interval of decomposition. However, the presence of dirty oil had little impact on activation energy. These findings indicated a significant synergistic relationship between straw and dirty oil, and it was practicable for co-pyrolysis from the viewpoint of thermal and kinetics analysis.

scholarly journals Kinetics of Hydrodesulfurization of Dibenzothiophene on Sulfided Commercial Co-Mo/γ-Al2O3 Catalyst

2006 ◽  
Vol 3 (1) ◽  
pp. 38 ◽  
Author(s):  
Y.S. Al-Zeghayer ◽  
B.Y. Jibril
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Reaction Temperature ◽  
Reaction Network ◽  
Order Model ◽  
First Order ◽  
Catalytic Sites ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Al2o3 Catalyst

Kinetics of hydrodesulfurization of dibenzothiophene (DBT) has been studied on a commercial CoMo/γ-Al2O3 catalyst at 633 - 683 K and 10 atm. A low DBT concentration typically obtained in hydrodesulfurization operations was used. Pseudo-first-order model was found to fit the experimental data for the consumption of DBT. The activation energy for the conversion of DBT was found to be 51.7 kcal/mol. Biphenyl (BP) and cyclohexylbenzene (CHB) were obtained as dominant products. For the reaction network, both parallel and parallel-sequential routes were explored. The latter was found to give a better description of the BP and CHB distributions. The ratio of BP to CHB depended on the reaction temperature. The values of activation energies of DBT hydrogenolysis to BP (EBP), DBT hydrogenation to CHB (ECHB1) and hydrogenation of BP to CHB (ECHB2) were found to be in a decreasing order of ECHB2 > EBP > ECHB1. The result suggests the presence of different catalytic sites leading to the two products on the catalysts. 

scholarly journals Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

2014 ◽  
Vol 27 (4) ◽  
pp. 213-216 ◽  
Author(s):  
Maria Zun ◽  
Dorota Dwornicka ◽  
Katarzyna Wojciechowska ◽  
Katarzyna Swiader ◽  
Regina Kasperek ◽  
...  
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Decomposition Rate ◽  
Aqueous Hydrogen Peroxide ◽  
Decomposition Rate Constant ◽  
First Order ◽  
First Order Kinetics ◽  
C 30 ◽  
The Stability ◽  
Kinetics Of

Abstract In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w) of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w) of urea had the best constancy.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

STUDIES ON HOMOGENEOUS FIRST ORDER GAS REACTIONS: II. THE DECOMPOSITION OF THE ISOMERIC ESTERS BUTYLIDENE DIACETATE AND ETHYLIDENE DIPROPIONATE

1932 ◽  
Vol 6 (4) ◽  
pp. 417-427 ◽  
Author(s):  
C. C. Coffin
Keyword(s):  
Activation Energy ◽  
Degrees Of Freedom ◽  
Maximum Energy ◽  
Velocity Measurements ◽  
First Order ◽  
Gas Reactions ◽  
Points Of View ◽  
The Stability ◽  
Future Work ◽  
Internal Degrees Of Freedom

The gaseous decompositions of the esters butylidene diacetate and ethylidene dipropionate have been studied from points of view previously outlined in papers on the decomposition of ethylidene diacetate (2, 3). The decomposition velocities have been measured at initial pressures of from 5 to 56 cm. of mercury and at temperatures between 211 and 265 °C. The reactions are homogeneous and of the first order. They agree with the Arrhenius equation and give 100% yields (within experimental error) of an aldehyde and an anhydride. The preparation of the compounds and improvements in the technique of the velocity measurements are described.While the specific velocities of the three reactions at any temperature are somewhat different, their activation energies are the same. It is suggested that in the case of such simple reactions, which are strictly localized within the molecular structure, the activation energy can be identified as the maximum energy that the reactive bonds may possess and still exist; i.e., it may be taken as a measure of the stability of the bonds which are broken in the reaction. The suggestion is also made that for a series of reactions which have the same activation energy, the specific velocities can be taken as a relative measure of the number of internal degrees of freedom that contribute to the energy of activation. On the basis of these assumptions it becomes possible to use reaction-velocity measurements for the investigation of intramolecular energy exchange. The theoretical significance of the data is further discussed and the scope of future work in this connection is indicated.The monomolecular velocity constants (sec−1) of the decomposition of ethylidene diacetate, ethylidene dipropionate and butylidene diacetate are given respectively by the equations [Formula: see text], [Formula: see text], and [Formula: see text].

scholarly journals Kinetics and mechanism of sol-gel transformation between some trivalent- and tetravalent-metal ions and Sodium alginate Anionic polyelectrolyte with formation of coordination Biopolymeric structure polymembranes Hydrogels of Capillary Structures Ex

2007 ◽  
Vol 3 (1) ◽  
pp. 133-142 ◽  
Author(s):  
Ishaq Abdullah Zaafarany
Keyword(s):  
Sodium Alginate ◽  
Metal Ion ◽  
Sol Gel ◽  
Coordination Geometry ◽  
Large Excess ◽  
First Order ◽  
Pseudo First Order ◽  
The Stability ◽  
Kinetics Of ◽  
Overall Kinetics

Abstract          The kinetics of sol-gel transformation between A13+, La 3+ and Th4+ metal ion electrolytes and sodium alginate sol have been studied complexometrically at various  temperatures. In the presence of a large excess of sodium alginate sol concentration over that of metal ion electrolyte, the pseudo first–order plots of exchange showed sigmoidal curves with two distinct stages. The initial part was relatively fast and curved significantly at early times, followed by a slow decrease in the rates of exchange over longer time periods. The rate constants of gelation showed second-order overall kinetics which was first order in the concentration of both reactants. The thermodynamic parameters have been evaluated and tentative gelation mechanisms consistent with the kinetic results of gelation are suggested. The stability of these ionotropic metal-alginate complexes has been discussed in terms of the coordination geometry and strength of chelated bonds.

Kinetics and Activation Parameters for the Alkaline Aqueous Rearrangement of Trichorfon [O,O-Dimethyl-(2,2,2-Trichloro-1-Hydroxyethyl) Phosphonate] to Dichlorvos [O,O-Dimethyl-O-(2,2-Dichloroethenyl)Phosphate]

2001 ◽  
Vol 36 (3) ◽  
pp. 589-604 ◽  
Author(s):  
Julian M. Dust ◽  
Christopher S. Warren
Keyword(s):  
Activation Energy ◽  
High Pressure ◽  
Activation Parameters ◽  
Base Catalysis ◽  
Rearrangement Product ◽  
Exponential Factor ◽  
First Order ◽  
Pseudo First Order ◽  
Order Plot ◽  
Kinetics Of

Abstract The kinetics of the alkaline rearrangement of O,O-dimethyl-(2,2,2-trichloro-1- hydroxyethyl)phosphonate, (trichlorfon, 1), the active insecticidal component in such formulations as Dylox, was followed at 25±0.5°C by high pressure liquid chromatography (UV-vis detector, 210 nm). The rearrangement product, O,Odimethyl- O-(2,2-dichloroethenyl)phosphate (dichlorovos, 2), which is a more potent biocide than trichlorfon, undergoes further reaction, and the kinetics, consequently, cannot be treated by a standard pseudo-first-order plot. A two-point van't Hoff (initial rates) method was used to obtain pseudo-first-order rate constants (kѱ) at 25, 35 and 45°C: 2.6 × 10-6, 7.4 × 10-6 and 2.5 × 10-5 s-1, respectively. Arrhenius treatment of this data gave an activation energy (Ea) of 88 kJ·mol-1 with a pre-exponential factor (A) of 5.5 × 109 s-1. Kinetic trials at pH 8.0 using phosphate and tris buffer systems show no buffer catalysis in this reaction and indicate that the rearrangement is subject to specific base catalysis. Estimates are reported for pseudo-first-order half-lives for trichlorfon at pH 8.0 for environmental conditions in aqueous systems in the Corner Brook region of western Newfoundland, part of the site of a recent trichlorfon aerial spray program.

Conductivities of Room Temperature Molten Salts Containing ZnCl2, Measured by a Computerized Direct Current Method

2002 ◽  
Vol 57 (3-4) ◽  
pp. 129-135
Author(s):  
Hsin-Yi Hsu ◽  
Chao-Chen Yang
Keyword(s):  
Activation Energy ◽  
Direct Current ◽  
Molten Salts ◽  
Room Temperature ◽  
Current Method ◽  
Cross Linking ◽  
Infra Red ◽  
Different Temperatures ◽  
The Stability ◽  
Benzyltriethylammonium Chloride

The conductivities of the binary room-temperature molten salt (RTMS) systems ZnCl2-N-nbutylpyridinium chloride (BPC), ZnCl2 -1-ethyl-3-methylimidazolium chloride (EMIC) and ZnCl2 - benzyltriethylammonium chloride (BTEAC) have been measured at different temperatures and compositions by a d.c. four-probes method. The conductivities of the three RTMS are in the order ZnCl2-EMIC > ZnCl2-BPC > ZnCl2-BTEAC. In ZnCl2-BPC the conductivity at 70 to 150 °C, is maximal for 40 mol% ZnCl2. In ZnCl2 - EMIC, the conductivity below 130 °C is almost constant for 30 to 50 mol% ZnCl2 and has the lowest activation energy 25.21 kJ/mol. For these two systems, the conductivities decrease rapidly beyond 50 mol% ZnCl2 owing to the rapid increase in cross-linking and resultant tightening of the polyelectrolyte structure. As to the ZnCl2-BTEAC system, the conductivities at 110 - 150 °C decrease slowly for 30 - 60 mol% ZnCl2. The conductivities of the ZnCl2-EMICmelt are compared with those of the AlCl3-EMIC melt previously studied. The stability of the ZnCl2-EMIC melt system is explored by the effect of the environment on the conductivity and the Far Transmission Infra Red (FTIR) spectrum. It reveals that the effect is slight, and that the ZnCl2-EMIC melt may be classified as stable.

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