共查询到20条相似文献,搜索用时 31 毫秒
1.
Melda Altikatoglu Candan Arioz Yeliz Basaran Huriye Kuzu 《Central European Journal of Chemistry》2009,7(3):423-428
Stabilization of Horseradish Peroxidase (HRP; EC 1.11.1.7) against temperature and pH via the formation of the conjugates
obtained by multipoint covalent bonding of dextran aldehyde (DA) to the enzyme were studied. Hence, three different molar
weighted dextrans (17.5 kD, 75 kD, 188 kD) were covalently bonded to purified enzyme with different molar ratios (nHRP/nDA 20/1, 10/1, 1/1, 1/5, 1/10, 1/15, 1/20). The thermal stabilities of the obtained conjugates were evaluated with the activities
determined at different temperatures (25, 30, 35, 40, 50, 60, 70, 80°C) applying 60 minutes incubation time. Conjugates formed
were characterized by gel-permeation chromatography (GPC) and fluorescence techniques. The conjugate synthesized using dextran
75 kDa with nHRP/nDA 1/10 molar ratio showed better thermal stability than other conjugates and purified enzyme at pH 7. This conjugate also has
wider activity pH range than purified enzyme. In addition, mentioned conjugate at pH 7 had very long storage lifetime compared
to purified enzyme at +4°C and room temperature; which is considered a favorable feature for usage in practice.
相似文献
2.
The covalent conjugates of cellulase from Aspergillus niger were prepared with various molar ratios by using dextran. The conjugate (nE/nD: 1/5) showed higher activity than purified enzyme at all temperatures after 1 h of incubation and its activity could also be measured at higher temperature. Also, this conjugate lost only 60% activity in 2 h at 70°C in comparison to the purified enzyme, which lost all its activity. In addition, conjugation protected cellulase against denaturation in the presence of sodium dodecylsulfate (residual activity of about 80%) and inactivation by air bubbles (residual activity of about 50% for 4 h). 相似文献
3.
Yanlei Dong Xianhong Wang Xiaojiang Zhao Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2012,50(2):362-370
Poly(ether carbonate)s (PPCs) with carbonate unit (CU) content ranging from 57.8 to 97.1% and number average molecular weight (Mn) around 100 kg/mol were conveniently prepared via copolymerization of CO2 and propylene oxide under combinatorial catalyst of rare earth ternary (RET) complex and double metal cyanide (DMC) complex. Enhancement of catalytic activity and reduction of propylene carbonate byproduct were realized due to synergetic effect of the two metal catalysts, where DMC can be activated in the presence of RET. Solubility fractionation confirmed that the obtained PPCs were copolymers, not physical blends of each polymer. Thermal performances of the PPCs were closely related to their CU content, their glass transition temperatures (Tg) were tunable in the range of 6.7–36.3 °C, which decreased with decreasing CU content, while their thermal stabilities were enhanced significantly, an increase of 50.5 °C in 50% weight loss temperature was observed when CU content decreased from 97.1 to 57.8%. Both shear storage modulus and complex viscosity increased with increasing CU content, which became more obvious at lower frequency, featuring well with the CU content in the PPCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
4.
Deise Juliana Kolling Willian Alexandre Suguino Fábio Cristiano Angonesi Brod Ana Carolina Maisonnave Arisi 《Applied biochemistry and biotechnology》2011,163(2):304-312
A recombinant esterase from Lactobacillus plantarum was immobilized on hydrophobic support polypropylene Accurel MP1000 by adsorption. Adsorption efficiency was 83%, and the
immobilized protein was 12.4 mg/g of support. Esterase activity was determined using p-nitrophenyl butyrate as substrate, and highest activities were observed at 50 °C for immobilized enzyme and 30 °C for free
enzyme extract. Concerning thermal stability, after enzyme incubation at 80 °C for 30 min, immobilized and free enzyme retained
91% and 56% of initial activity, respectively. Immobilized enzyme presented lower V
max and higher K
m than free enzyme. Protein was not released from the support, and esterase activity increased after 3 cycles of reuse. 相似文献
5.
Abstract Immobilization of pepsin on crosslinked resinous materials SRF (salicylic acid-resorcinol-formaldehyde), Amberlite IRA-400, and poly-(vinyl alcohol) is reported. Enzyme concentration, pH of the coupling medium, and nature and concentration of crosslinking agents were optimized for the better retention of activity of immobilized pepsin. The immobilized systems were characterized through pH, thermal, and storage stabilities. Michaelis constant (K m) and maximum reaction velocity (V m) for the free and immobilized enzymes were calculated from Lineweaver-Burk plots. Effect of temperature on enzyme activity was studied, and the thermoinactivation constant (K ti) and energy of activation (E a) for free and immobilized enzymes were also calculated. The immobilized pepsin was used in a continuous fluidized bed reactor for the study of clotting of skimmed milk. Rate of coagulation was considerably high for the treated milk sample at 50°C and pH 6–6.2. 相似文献
6.
Cleide M. F. Soares Heizir F. de Castro Juliana E. Itako Flavio F. De Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》2005,123(1-3):845-859
Candida rugosa lipase was entrapped in silica sol-gel particles prepared by hydrolysis of methyltrimethoxysilane and assayed by p-nitrophenyl palmitate hydrolysis, as a function of pH and temperature, giving pH optima of 7.8 (free enzyme) and 5.0–8.0
(immobilized enzyme). The optimum temperature for the immobilized enzyme (50–55°C) was 19°C higher than for the free enzyme.
Thermal, operational, and storage stability were determined with n-butanol and bytyric acid, giving at 45°C a half-life 2.7 times greater for the immobilized enzyme; storage time was 21 d
at room temperature. For ester synthesis, the optimum temperature was 47°C, and high esterification conversions were obtained
under repeated batch cycles (half-life of 138 h). 相似文献
7.
Properties of pectinesterase and endo-d-polygalacturonase coimmobilized in a porous glass support 总被引:1,自引:0,他引:1
A. Manjón J. L. Iborra C. Romero M. Cánovas 《Applied biochemistry and biotechnology》1992,37(1):19-31
Derivatives of pectinesterase and polygalacturonase, both individually immobilized and coimmobilized, were obtained and characterized.
Homologous soluble systems were also studied to establish differences between the effect of the immobilization process and
the presence of the other enzyme. Immobilization or coimmobilization did not change the optima pH or temperature for the enzymes.
However, optimum ionic strength was displaced toward higher values for immobilized pectinesterase, while for polygalacturonase
immobilization resulted in a wider range for activity.K
m
value remained nearly unchanged for pectinesterase, and decreased for polygalacturonase. TheV
m
value decreased with the immobilization process for the two enzymes, except for polygalacturonase immobilization in presence
of pectinesterase. Soluble pectinesterase activity showed a competitive inhibition by polygalacturonic acid (Ki = 0.44 mg/mL). Either immobilization or presence of polygalacturonase rendered the enzyme insensitive to the inhibitory effect.
Thermal stability of pectinesterase was not improved after immobilization. On the contrary, the thermal stability of endo-D-polygalacturonase
was improved slightly by presence of pectinesterase, and in a greater extent by immobilization. Individually immobilized and
coimmobilized pectinesterase activities kept 90 and 60%, respectively, of their initial values after more than one year stored
at 3-5 °C. The two endo-D-polygalacturonase derivatives showed the same activity decay pattern along 10 mo storage at 3-5
°C. The two immobilized pectinesterase derivatives showed similar operational stabilities during continuous operation. The
presence of pectinesterase remarkably increased the operational stability of the immobilized endo-D-poly galacturonase. 相似文献
8.
Ke Li Xiao Ting Liu Yun Fei Zhang Donglei Liu Xin Yu Zhang Song Mei Ma Juan M. Ruso Zhenghua Tang Zhen Bin Chen Zhen Liu 《先进技术聚合物》2019,30(1):86-93
In this work, the relationships between catalytic performances of penicillin G acylase (PGA) and the molar ratio of carrier, thermo‐sensitive tri‐block polymer, poly (N,N‐diethylacrylamide‐b‐ β‐hydroxyethyl methacrylate‐b‐glycidyl methacrylate) (PDEA‐b‐PHEMA‐b‐PGMA) were studied firstly, and result documented the optimal molar ratio was nDEA:nHEMA:nGMA = 100:47:24, which presented a suitable lower critical solution temperature (LCST) of 35°C and the activity retention ratio of 80.62% (±0.50%). Based on the suitable carrier, immobilization conditions were investigated and optimized. When pH of solution, concentration of PGA, immobilized time, and immobilization temperature were 8.0, 1/10 (m/v), 16 hours, and 36°C, respectively, enzyme loading capacity (L), enzyme activity (Ea), and activity retention ratio (Ar) of PGA arrived at the highest value of 21 223 U, 16 199 U/g, and 93.50% (±0.50%), respectively. Besides, the response rate (Rr) of immobilized PGA was the same as free PGA, the reusable stability (Rs) was 77.00% (±1.00%) after using for 11 times, which indicated that the carrier has better compatibility with L, Ar, Rs, and Rr. 相似文献
9.
A novel hybrid epoxy/nano CaCO3 composite matrix for catalase immobilization was prepared by polymerizing epoxy resin in the presence of CaCO3 nanoparticles. The hybrid support was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. Catalase was successfully immobilized onto epoxy/nano CaCO3 support with a conjugation yield of 0.67?±?0.01 mg/cm2 and 92.63?±?0.80 % retention of activity. Optimum pH and optimum temperature of free and immobilized catalases were found to be 7.0 and 35 °C. The value of K m for H2O2 was higher for immobilized enzyme (31.42 mM) than native enzyme (27.73 mM). A decrease in V max value from 1,500 to 421.10 μmol (min mg protein)?1 was observed after immobilization. Thermal and storage stabilities of catalase improved immensely after immobilization. Immobilized enzyme retained three times than the activity of free enzyme when kept at 75 °C for 1 h and the half-life of enzyme increased five times when stored in phosphate buffer (0.01 M, pH 7.0) at 5 °C. The enzyme could be reused 30 times without any significant loss of its initial activity. Desorption of catalase from the hybrid support was minimum at pH 7.0. 相似文献
10.
Melda Altikatoglu Yeliz Basaran Candan Arioz Ayse Ogan Huriye Kuzu 《Applied biochemistry and biotechnology》2010,160(8):2187-2197
Multipoint covalent bonding of glucose oxidase (EC 1.1.3.4) to hydrophilic natural polymer dextran and optimization of procedures
to obtain, with enhanced temperature and pH stabilities, were studied. Purified enzyme was conjugated with various molecular
weight dextrans (17.5, 75, and188 kD) in a ratio of 20:1, 10:1, 1:1, 1:5, 1:10, 1:15, and 1:20. After 1 h of incubation at
pH 7, the activities of purified enzyme and conjugates were determined at different temperatures (25°C, 30°C, 35°C, 40°C,
50°C, 60°C, 70°C, and 80°C), and the results were evaluated for thermal resistance. Increases in temperature from 25°C to
50°C did not change the activities of the conjugates. The conjugate, which was prepared with 75 kDa dextran in a molar ratio
of 1:5, showed the highest thermal resistance and even the activity still remains at 80°C at pH 7.0. This conjugate also displayed
activity in a wide pH range (pH 4.0–7.0) at high temperatures. Conjugate, which was synthesized with 75 kDa dextran in a molar
ratio of 1:5, appears to be feasible and useful for biotechnological applications. 相似文献
11.
Maalej I Belhaj I Masmoudi NF Belghith H 《Applied biochemistry and biotechnology》2009,158(1):200-212
A thermostable xylanase from a newly isolated thermophilic fungus Talaromyces thermophilus was purified and characterized. The enzyme was purified to homogeneity by ammonium sulfate precipitation, diethylaminoethyl
cellulose anion exchange chromatography, P-100 gel filtration, and Mono Q chromatography with a 23-fold increase in specific
activity and 17.5% recovery. The molecular weight of the xylanase was estimated to be 25kDa by sodium dodecyl sulfate–polyacrylamide
gel electrophoresis and gel filtration. The enzyme was highly active over a wide range of pH from 4.0 to 10.0. The relative
activities at pH5.0, 9.0, and 10.0 were about 80%, 85.0%, and 60% of that at pH7.5, respectively. The optimum temperature
of the purified enzyme was 75°C. The enzyme showed high thermal stability at 50°C (7days) and the half-life of the xylanase
at 100°C was 60min. The enzyme was free from cellulase activity. K
m and V
max values at 50°C of the purified enzyme for birchwood xylan were 22.51mg/ml and 1.235μmol min−1 mg−1, respectively. The enzyme was activated by Ag+, Co2+, and Cu2+; on the other hand, Hg2+, Ba2+, and Mn2+ inhibited the enzyme. The present study is among the first works to examine and describe a secreted, cellulase-free, and
highly thermostable xylanase from the T. thermophilus fungus whose application as a pre-bleaching aid is of apparent importance for pulp and paper industries. 相似文献
12.
S1 nuclease fromAspergillus oryzae (EC 3.1.30.1) was coupled to gelatin-alginate composite matrix using the residual free aldehyde groups on the surface of
glutaraldehyde crosslinked matrix. The immobilized enzyme retained approximately 10% activity of the soluble enzyme. When
partially purified enzyme was bound to the matrix, the immobilized preparation did not show any detectable enzyme activity.
However, the activity could be restored when the coupling was carried out in the presence of a coprotein or substrate. The
optimum pH of the immobilized S1 nuclease shifted to 3.8 from 4.3 for the soluble enzyme. Also, optimum temperature increased
to 65°C after immobilization. Bound S1 nuclease showed increased pH and temperature stabilities. Immobilization brought about
a twofold decrease in the Michaelis-Menton constant (K
m). 相似文献
13.
Lactose has been hydrolyzed using covalently immobilized β-galactosidase on thermally stable carrageenan coated with chitosan
(hydrogel). The hydrogel’s mode of interaction was proven by Fourier transform infrared spectroscopy, differential scanning
calorimetry (DSC), and Schiff’s base formation. The DSC thermogram proved the formation of a strong polyelectrolyte complex
between carrageenan and chitosan followed by glutaraldehyde as they formed one single peak. The modification of carrageenan
improved the gel’s thermal stability in solutions from 35 °C to 95 °C. The hydrogel has been proven to be efficient for β-galactosidase
immobilization where 11 U/g wet gel was immobilized with 50% enzyme loading capacity. Activity and stability of free and immobilized
β-galactosidase towards pH and temperature showed marked shifts in their optimum pH from 4.5–5 to 5–5.5 and temperature from
50 °C to 45–55 °C after immobilization, which reveals higher catalytic activity and reasonable stability at wider pHs and
temperatures. The apparent K
m of the immobilized enzyme increased from 13.2 to 125 mM, whereas the V
max increased from 3.2 to 6.6 μmol/min compared to the free enzyme, respectively. The free and immobilized enzymes showed lactose
conversion of 87% and 70% at 7 h, respectively. The operational stability showed 97% retention of the enzyme activity after
15 uses, which demonstrates that the covalently immobilized enzyme is unlikely to leach. The new carrier could be suitable
for immobilization of other industrial enzymes. 相似文献
14.
《中国化学会会志》2018,65(6):771-779
Inulin hydrolysis was performed by inulinase from Aspergillus niger covalently immobilized on magnetite nanoparticles (Fe3O4) covered with soy protein isolate (Fe3O4/SPI) functionalized by bovine serum albumin (Fe3O4/SPI/BSA) nanoparticles as a new bio‐functional carrier. The specific activity and protein content of the immobilized enzyme were 25.99 U/mg and 3.52 mg/mL, respectively, with 80% enzyme loading. The immobilized inulinase showed maximum activity at 45 °C, which is 5 °C higher than the optimum temperature of the free enzyme. Also, the optimum pH of the immobilized enzyme shifted from 6 to 5.5, which is more acidic compared to that of the free enzyme. The Km value of immobilized inulinase decreased to 2.03 mg/mL. Thermal stability increased considerably at 65 and 75 °C, and a 5.13‐fold rise was detected in the enzyme half‐life at 75 °C after immobilization. Moreover, 80% of initial activity of immobilized inulinase remained after 10 cycles of hydrolysis. 相似文献
15.
Y. Li N. Obando F. Tschen R. J. Morgan 《Journal of Thermal Analysis and Calorimetry》2006,85(1):125-129
Thermal analysis of phenylethynyl end-capped imide oligomer AFR-PEPA-4
was performed to characterize cure reaction, thermal stabilities and semicrystalline
behavior of AFR-PEPA-4 oligomer and its cured polyimide. Cured AFR-PEPA-4
polyimide showed high T
gs
up to 418°C. Both AFR-PEPA-4 oligomer and polyimide exhibit excellent
thermal stabilities comparable to PETI-5 polyimides. AFR-PEPA-4 imide oligomer
has a T
m of 330°C
and exhibits spherulite crystalline morphology in the film. The crystallinity
in AFR-PEPA-4 films could not be regenerated under any annealing conditions
after the initial melt. 相似文献
16.
Masayoshi Itoh Kenji Iwata Jun‐Ichi Ishikawa Hiroshi Sukawa Hideaki Kimura Koichi Okita 《Journal of polymer science. Part A, Polymer chemistry》2001,39(15):2658-2669
Nine new kinds of thermosetting polymers with the Si(H)? C?C unit were synthesized by dehydrogenative polycondensation reactions between hydrosilanes and diethynyl compounds in the presence of a magnesia catalyst. Phenylsilane, silane, vinylsilane, and n‐octylsilane were used as the hydrosilanes, and 1,3‐diethynylbenzene, 1,4‐diethynylbenzene, 4,4′‐diethynyldiphenyl ether, and 1,3‐diethynyl‐1,1,3,3‐tetramethyldisiloxane were used as the diethynyl compounds. All the polymers were thermosetting, highly heat‐resistant, easily soluble in a solvent, and moldable. In particular, ? Si(R)H? C?C? C6H4? C?C? (R = H or CH?CH2) showed high thermal stability; the temperature of 5% weight loss was greater than 800 °C, and the residue at 1000 °C was over 90%. The thermal stabilities of the polymers were attributed to the crosslinking reaction of the Si? H and C?C bonds. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2658–2669, 2001 相似文献
17.
Xylanase from Bacillus pumilus strain MK001 was immobilized on different matrices following varied immobilization methods. Entrapment using gelatin (GE)
(40.0%), physical adsorption on chitin (CH) (35.0%), ionic binding with Q-sepharose (Q-S) (45.0%), and covalent binding with
HP-20 beads (42.0%) showed the maximum xylanase immobilization efficiency. The optimum pH of immobilized xylanase shifted
up to 1.0 unit (pH 7.0) as compared to free enzyme (pH 6.0). The immobilized xylanase exhibited higher pH stability (up to
28.0%) in the alkaline pH range (7.0–10.0) as compared to free enzyme. Optimum temperature of immobilized xylanase was observed
to be 8 °C higher (68.0 °C) than free enzyme (60.0 °C). The free xylanase retained 50.0% activity, whereas xylanase immobilized
on HP-20, Q-S, CH, and GE retained 68.0, 64.0, 58.0, and 57.0% residual activity, respectively, after 3 h of incubation at
80.0 °C. The immobilized xylanase registered marginal increase and decrease in K
m and V
max values, respectively, as compared to free enzyme. The immobilized xylanase retained up to 70.0% of its initial hydrolysis
activity after seven enzyme reaction cycles. The immobilized xylanase was found to produce higher levels of high-quality xylo-oligosaccharides
from birchwood xylan, indicating its potential in the nutraceutical industry. 相似文献
18.
Cline Farcet Julien Nicolas Bernadette Charleux 《Journal of polymer science. Part A, Polymer chemistry》2002,40(24):4410-4420
The controlled free‐radical homopolymerization of n‐butyl acrylate was studied in aqueous miniemulsions at 112 and 125 °C with a low molar mass alkoxyamine unimolecular initiator and an acyclic β‐phosphonylated nitroxide mediator, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. The polymerizations led to stable latices with 20 wt % solids and were obtained with neither coagulation during synthesis nor destabilization over time. However, in contrast to latices obtained via classical free‐radical polymerization, the average particle size of the final latices was large, with broad particle size distributions. The initial [SG1]0/[alkoxyamine]0 molar ratio was shown to control the rate of polymerization. The fraction of SG1 released upon macroradical self‐termination was small with respect to the initial alkoxyamine concentration, indicating a very low fraction of dead chains. Average molar masses were controlled by the initial concentration of alkoxyamine and increased linearly with monomer conversion. The molar mass distribution was narrow, depending on the initial concentration of free nitroxide in the system. The initiator efficiency was lower than 1 at 112 °C but was very significantly improved when either a macroinitiator was used at 112 °C or the polymerization temperature was raised to 125 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4410–4420, 2002 相似文献
19.
《Journal of Coordination Chemistry》2012,65(15):2583-2591
A coordination compound based on tetrazole acetic acid (Htza) and bismuth(III), [Bi(tza)3] n , was synthesized and characterized by single crystal X-ray diffraction analysis, elemental analysis, FT-IR, and 1H NMR spectroscopy. The crystallographic data show that the crystal belongs to monoclinic, P21/n space group, a?=?0.91968(19)?nm, b?=?0.94869(19)?nm, c?=?1.7824(4)?nm, β?=?101.488(3)°, and Z?=?4. The central bismuth(III) is nine-coordinate by three nitrogens from three tetrazole rings and six oxygens of the carboxylate of another three tza? ions, with each tza? tridentate, chelating, bridging coordination. The coordination bonds and the intramolecular hydrogen bonds make the complex pack into a layered structure in polymer form. The thermal decomposition mechanism of the title complex was investigated by DSC and TG-DTG techniques. Under nitrogen at a heating rate of 10°C?min?1, thermal decomposition of the complex contains two intense exothermic processes between 217.4°C and 530.3°C in the DSC curve; the final decomposed residue at 570°C was Bi2O3. Sensitivity tests showed that [Bi(tza)3] n was sensitive to impact and flame stimulus. 相似文献
20.
Brígida AI Pinheiro AD Ferreira AL Gonçalves LR 《Applied biochemistry and biotechnology》2008,146(1-3):173-187
An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme
offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants
of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after
2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined.
CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 °C, as half-lives
(t
1/2) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational
stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate
hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle.
However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared
to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction. 相似文献