共查询到20条相似文献,搜索用时 31 毫秒
1.
Catherine Rafin Etienne VeignieAntoine Fayeulle Gheorghe Surpateanu 《Bioresource technology》2009,100(12):3157-3160
The interest of simultaneously combining chemical (Fenton’s reaction) and biological treatments for the degradation of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) has been studied in laboratory tests. An optimal concentration of 1.5 × 10−3 M H2O2 as Fenton’s reagent was firstly determined as being compatible with the growth of Fusarium solani, the Deuteromycete fungus used in the biodegradation process. For the enhancement of BaP solubilisation, cyclodextrins were also used in the performed tests. The best degradation performance was achieved through the use of 5 × 10−3 M hydroxypropyl-β-cyclodextrin (HPBCD) in comparison with randomly methylated-β-cyclodextrin (RAMEB). When Fenton’s treatment was combined with biodegradation, a beneficial effect on BaP degradation (25%) was obtained in comparison with biodegradation alone (8%) or with chemical oxidation alone (16%) in the presence of HPBCD for 12 days of incubation. 相似文献
2.
The effect of oxidative pretreatment on cellulose degradation by Poria placenta and Trichoderma reesei cellulases 总被引:1,自引:0,他引:1
The possible role of hydrogen peroxide in brown-rot decay was investigated by studying the effects of pretreatment of spruce
wood and microcrystalline Avicel cellulose with H2O2 and Fe2+ (Fenton's reagent) on the subsequent enzymatic hydrolysis of the substrates. A crude endoglucanase preparation from the brown-rot
fungus Poria placenta, a purified endoglucanase from Trichoderma reesei and a commercial Trichoderma cellulase were used as enzymes. Avicel cellulose and spruce dust were depolymerized in the H2O2/Fe2+ treatment. Mainly hemicelluloses were lost in the treatment of spruce dust. The effect of the pretreatment on subsequent
enzymatic hydrolysis was found to depend on the nature of the substrate and the enzyme preparation used. Pretreatment with
H2O2/Fe2+ clearly increased the amount of enzymatic hydrolysis of spruce dust with both the endoglucanases and the commercial cellulase.
In all cases the amount of hydrolysis was increased about threefold. The hydrolysis of Avicel with the endoglucanases was
also enhanced, whereas the hydrolysis with the commercial cellulase was decreased.
Received: 23 December 1996 / Received revision: 17 April 1997 / Accepted: 19 April 1997 相似文献
3.
B. Seshadri Sekhar C. K. Ramakrishna Kurup T. Ramasarma 《Journal of bioenergetics and biomembranes》1987,19(4):397-407
This is the first report on the generation of H2O2 by brown adipose tissue mitochondria. Flavin dehydrogenase-linked substrates like succinate, glycerol-1-phosphate, and fatty acyl CoA were good substrates for the reaction, while NAD+-linked substrates were less effective. In cold-acclimated animals the activity showed a substantial increase (2.5-fold). TheK
m andV
max of the reaction were considerably lower than those of the respective dehydrogenase. Metal ions, particularly Cu2+ and Fe2+ were potent inhibitors of the reaction. Nucleoside diphosphates, which were inhibitors by themselves, potentiated the inhibitory action of Fe2+ ions. In most of the properties, the H2O2 generator of brown adipose tissue mitochondria resembled that of liver mitochondria. 相似文献
4.
M. R. T. Palmroth J. H. Langwaldt T. A. Aunola A. Goi U. Münster J. A. Puhakka T. A. Tuhkanen 《Biodegradation》2006,17(2):29-39
This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified
Fenton’s reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria
during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H2O2 on was studied. In both experiments the H2O2 dosage was 0.4 g H2O2/g soil. In completely H2O2−saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column.
In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially
saturated soil, with only 25% in 10 days. The effect of the modified Fenton’s reaction on the microbial activity in the soil
was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide
production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards
Vibrio fischeri increased as a result of the modified Fenton’s reaction. The activities of the microbial extracellular enzymes acetate- and
acidic phosphomono-esterase were lower in the incubated modified Fenton’s treated soil compared to extracellular enzyme activities
in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation
of soil in serum bottles at 20 °C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation
of organic compounds. In untreated soil 20–30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically
treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil. 相似文献
5.
Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca2+-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30 °C to 37 °C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca2+ ([Ca2+]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe2+-accumulation following pretreatment with FeSO4. Thus intracellular Fe2+-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe2+-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe2+-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37 °C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe2+-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe2+-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2 channels by Fe2+ may implicated in hemorrhagic brain injury via aggravation of inflammation, since Fe2+ is released by heme degradation under intracerebral hemorrhage. 相似文献
6.
Burton R. Andersen Liana Harvath 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,584(1):164-173
A simple chemical system consisting of FeSO4 and H2O2 (Fenton's reagent) was shown to emit light (chemiluminescence). The addition of tryptophan to the reaction markedly enhanced light production. Very little chemiluminescence was observed when H2O2 was omitted from the reaction and when ferric, instead of ferrous, ions were used. Hydroxyl radical (OH.) and singlet oxygen (1ΔgO2) quenchers suppressed chemiluminescence of the FeSO4 + tryptophan + H2O2 system; and, deuterium oxide (2H2O) enhanced chemiluminescence of both FeSO4 reactions. These observations suggest that a radical chain reaction involving both OH. and 1ΔgO2 is responsible for the chemiluminescent reactions. Six iron-containing proteins, some of which are located within granulocytes, all emitted light in the presence of H2O2. Since iron and H2O2 are present in metabolically stimulated granulocytes, it is likely that chemiluminescent reactions similar to the ones demonstrated in this study account for part of the chemiluminescence of activated granulocytes. 相似文献
7.
Enhanced transformation of polycyclic aromatic hydrocarbons using a combined Fenton's reagent,microbial treatment and surfactants 总被引:5,自引:0,他引:5
Nadarajah N Van Hamme J Pannu J Singh A Ward O 《Applied microbiology and biotechnology》2002,59(4-5):540-544
The potential for using Fenton's reagent (H2O2 + Fe2+) as an advanced oxidation pretreatment process to enhance microbial transformation of two model polycyclic aromatic hydrocarbons,
anthracene and benzo[a]pyrene, in an aqueous system was evaluated. Fenton's reagent at a concentration of 0.5% H2O2 and 10 mM Fe2+ (molar ratio, 15:1) was most effective in transforming anthracene at pH 4. Application of non-ionic surfactants during Fenton's
pre-treatment was found to be more effective in the transformation of both anthracene and benzo[a]pyrene. The extent of removal
of substrates by a combined Fenton's–biotreatment was 2–4 times higher than with Fenton's treatment or biotreatment alone.
In a chemical–biological treatment train, 48 h of Fenton's pre-treatment in the presence of a non-ionic surfactant, followed
by 7 days of biological treatment resulted in 80–85% removal of PAHs (100 ppm).
Electronic Publication 相似文献
8.
M. Khosraneh A. Mahmoudi H. Rahimi K. Nazari A. A. Moosavi-Movahedi 《Journal of enzyme inhibition and medicinal chemistry》2013,28(6):677-684
The kinetics of microperoxidase-11 (MP-11) in the oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H2O2. Concentrations of substrates were so selected that: 1) the reaction was first-order in relation to benign substrate, AH and 2) high ratio of suicide substrate to the benign substrate, [H2O2]>>[AH]. Validation and reliability of the obtained kinetic equations were evaluated in various nonlinear and linear forms. Fitting of experimental data into the obtained integrated equation showed a close match between the kinetic model and the experimental results. Indeed, a similar mechanism to horseradish peroxidase was found for the suicide-peroxide inactivation of MP-11. Kinetic parameters of inactivation including the intact activity of MP-11, αi, and the apparent inactivation rate constant, ki, were obtained as 0.282 ± 0.006 min? 1 and 0.497 ± 0.013 min? 1 at [H2O2] = 1.0 mM, 27°C, phosphate buffer 5.0 mM, pH = 7.0. Results showed that inactivation of microperoxidase as a peroxidase model enzyme can occur even at low concentrations of hydrogen peroxide (0.4 mM). 相似文献
9.
Martina Paumann-Page Paul G. Furtmüller Stefan Hofbauer Louise N. Paton Christian Obinger Anthony J. Kettle 《Archives of biochemistry and biophysics》2013
Human myeloperoxidase (MPO) uses hydrogen peroxide generated by the oxidative burst of neutrophils to produce an array of antimicrobial oxidants. During this process MPO is irreversibly inactivated. This study focused on the unknown role of hydrogen peroxide in this process. When treated with low concentrations of H2O2 in the absence of reducing substrates, there was a rapid loss of up to 35% of its peroxidase activity. Inactivation is proposed to occur via oxidation reactions of Compound I with the prosthetic group or amino acid residues. At higher concentrations hydrogen peroxide acts as a suicide substrate with a rate constant of inactivation of 3.9 × 10−3 s−1. Treatment of MPO with high H2O2 concentrations resulted in complete inactivation, Compound III formation, destruction of the heme groups, release of their iron, and detachment of the small polypeptide chain of MPO. Ten of the protein’s methionine residues were oxidized and the thermal stability of the protein decreased. Inactivation by high concentrations of H2O2 is proposed to occur via the generation of reactive oxidants when H2O2 reacts with Compound III. These mechanisms of inactivation may occur inside neutrophil phagosomes when reducing substrates for MPO become limiting and could be exploited when designing pharmacological inhibitors. 相似文献
10.
Daniel V. Suzuki José M. Carter Maria Filomena A. Rodrigues Elda S. da Silva Alfredo E. Maiorano 《World journal of microbiology & biotechnology》2008,24(6):771-775
This work aimed at the study of purification of biopolymers produced by Burkholderia cepacia IPT64, through a chemical attack like an adjuvant procedure through chemical and enzymatic route. Enzymatic lysis using protease
was run on an enzyme/cell ratio of 0.02. Chemical attacks were performed as pre or post-treatment for enzymatic attacks, using
sodium dodecyl sulphate or hydrogen peroxide. The same chemicals and procedures were used alone as a control. Fenton’s reagent
was also tested as a chemical treatment. Using only one of the chemicals H2O2, Fenton’s reagent or SDS, the purity increase achieved values of 14%, 16% or 23%, respectively. When H2O2 or SDS were used as pre-treatment for the enzymatic attack, the results of purity increase achieved values of 58% for H2O2/cell ratio between 0.60 and 1.20, and 57% when SDS/cell ratio at 0.56 was used. In the case when H2O2 or SDS were used as post-treatment for the enzymatic attack, results of purity increase achieved 60% when the H2O2 was used at H2O2/cell ratio ranging between 0.30 and 0.60 and 71% when SDS was used at a ratio SDS/cell of 0.56. 相似文献
11.
Richard H. Stadler Jovanka Markovic Robert J. Turesky 《Biological trace element research》1995,47(1-3):299-305
The anti- and pro-oxidative effects of phenolic compounds and antioxidants were studied in two different in vitro model systems
utilizing ethyl linoleate and 2′-deoxyguanosine (2′-dG) as oxidative substrates, and a Fenton reaction (H2O2, Fe2+) to initiate oxidation. Oxidation of the biomolecules in both model systems exhibited dose dependency. In the 2′-dG assay,
oxidation was closely related to H2O2 generation, which occurred during autoxidation of the phenolics. Hydroxylating activity was greatly enhanced by Mn2+ and Cu2+, but not by Zn2+ or Co2+. Ethyl linoleate peroxidation was inhibited by low concentrations of catechol, quercitin, and instant coffee. However, peroxidation
was promoted by high concentrations of the same compounds, probably by recycling of chelated inactive Fe3+ to the active Fe2+ state. 相似文献
12.
Nitric oxide reductase (NOR) from P. denitrificans is a membrane-bound protein complex that catalyses the reduction of NO to N2O (2NO + 2e− + 2H+ → N2O + H2O) as part of the denitrification process. Even though NO reduction is a highly exergonic reaction, and NOR belongs to the superfamily of O2-reducing, proton-pumping heme-copper oxidases (HCuOs), previous measurements have indicated that the reaction catalyzed by NOR is non-electrogenic, i.e. not contributing to the proton electrochemical gradient. Since electrons are provided by donors in the periplasm, this non-electrogenicity implies that the substrate protons are also taken up from the periplasm. Here, using direct measurements in liposome-reconstituted NOR during reduction of both NO and the alternative substrate O2, we demonstrate that protons are indeed consumed from the ‘outside’. First, multiple turnover reduction of O2 resulted in an increase in pH on the outside of the NOR-vesicles. Second, comparison of electrical potential generation in NOR-liposomes during oxidation of the reduced enzyme by either NO or O2 shows that the proton transfer signals are very similar for the two substrates proving the usefulness of O2 as a model substrate for these studies. Last, optical measurements during single-turnover oxidation by O2 show electron transfer coupled to proton uptake from outside the NOR-liposomes with a τ = 15 ms, similar to results obtained for net proton uptake in solubilised NOR [U. Flock, N.J. Watmough, P. Ädelroth, Electron/proton coupling in bacterial nitric oxide reductase during reduction of oxygen, Biochemistry 44 (2005) 10711-10719]. NOR must thus contain a proton transfer pathway leading from the periplasmic surface into the active site. Using homology modeling with the structures of HCuOs as templates, we constructed a 3D model of the NorB catalytic subunit from P. denitrificans in order to search for such a pathway. A plausible pathway, consisting of conserved protonatable residues, is suggested. 相似文献
13.
M. Aktar Ali Fumihiko Yasui Seiichi Matsugo Tetsuya Konishi 《Free radical research》2013,47(5):429-438
The effect of lactic acid (lactate) on Fenton based hydroxyl radical (·OH) production was studied by spin trapping, ESR, and fluorescence methods using DMPO and coumarin-3-carboxylic acid (3-CCA) as the ·OH traps respectively. The ·OH adduct formation was inhibited by lactate up to 0.4mM (lactate/iron stoichiometry = 2) in both experiments, but markedly enhanced with increasing concentrations of lactate above this critical concentration. When the H2O2 dependence was examined, the DMPO-OH signal was increased linearly with H2O2 concentration up to 1 mM and then saturated in the absence of lactate. In the presence of lactate, however, the DMPO-OH signal was increased further with higher H2O2 concentration than 1 mM, and the saturation level was also increased dependent on lactate concentration. Spectroscopic studies revealed that lactate forms a stable colored complex with Fe3+ at lactate/Fe3+ stoichiometry of 2, and the complex formation was strictly related to the DMPO-OH formation. The complex formation did not promote the H2O2 mediated Fe3+ reduction. When the Fe3+-lactate (1:2) complex was reacted with H2O2, the initial rate of hydroxylated 3-CCA formation was linearly increased with H2O2 concentrations. All the data obtained in the present experiments suggested that the Fe3+-lactate (1:2) complex formed in the Fenton reaction system reacts directly with H2O2 to produce additional ·OH in the Fenton reaction by other mechanisms than lactate or lactate/Fe3+ mediated promotion of Fe3+/Fe2+ redox cycling. 相似文献
14.
Maximiliano J. Amenabar Daniel R. Colman Saroj Poudel Eric E. Roden Eric S. Boyd 《Environmental microbiology》2018,20(7):2523-2537
The thermoacidophilic Acidianus strain DS80 displays versatility in its energy metabolism and can grow autotrophically and heterotrophically with elemental sulfur (S°), ferric iron (Fe3+) or oxygen (O2) as electron acceptors. Here, we show that autotrophic and heterotrophic growth with S° as the electron acceptor is obligately dependent on hydrogen (H2) as electron donor; organic substrates such as acetate can only serve as a carbon source. In contrast, organic substrates such as acetate can serve as electron donor and carbon source for Fe3+ or O2 grown cells. During growth on S° or Fe3+ with H2 as an electron donor, the amount of CO2 assimilated into biomass decreased when cultures were provided with acetate. The addition of CO2 to cultures decreased the amount of acetate mineralized and assimilated and increased cell production in H2/Fe3+ grown cells but had no effect on H2/S° grown cells. In acetate/Fe3+ grown cells, the presence of H2 decreased the amount of acetate mineralized as CO2 in cultures compared to those without H2. These results indicate that electron acceptor availability constrains the variety of carbon sources used by this strain. Addition of H2 to cultures overcomes this limitation and alters heterotrophic metabolism. 相似文献
15.
In the absence of added Fe2+, the ATPase activity of isolatedSchizosaccharomyces pombe plasma membranes (5–7 μmolP
i per mg protein per min) is moderately inhibited by H2O2 in a concentration-dependent manner. Sizable inactivation occurs only at 50–80 mmol/L H2O2. The process, probably a direct oxidative action of H2O2 on the enzyme, is not induced by the indigenous membrane-bound iron (19.3 nmol/mg membrane protein), is not affected by the
radical scavengers mannitol and Tris, and involves a decrease of both theK
m of the enzyme for ATP and theV of ATP splitting. On exposing the membranes to the Fenton reagent (50 μmol/L Fe2+ +20 mmol/L H2O2), which causes a fast production of HO− radicals, the ATPase is 50–60% inactivated and 90% of added Fe2+ is oxidized to Fe3+ within 1 min. The inactivation occurs only when Fe2+ is added before H2O2 and can thus bind to the membranes. The lack of effect of radical scavengers (mannitol, Tris) indicates that HO− radicals produced in the bulk phase play no role in inactivation. Blockage of the inactivation by the iron chelator deferrioxamine
implies that the process requires the presence of Fe2+ ions bound to binding sites on the enzyme molecules. Added catalase, which competes with Fe2+ for H2O2, slows down the inactivation but in some cases increases its total extent, probably due to the formation of the superoxide
radical that gives rise to delayed HO− production. 相似文献
16.
《Biochimica et Biophysica Acta (BBA) - Enzymology》1980,611(1):51-60
Product inhibition of lysyl hydroxylase (peptidyllysine, 2-oxoglutarate:oxygen 5-oxidoreductase, EC 1.14.11.4) was studied with succinate, CO2, dehydroascorbate and hydroxylysine-rich polypeptide chains. The product inhibition patterns and addition data are consistent with a reaction mechanism involving an ordered binding of Fe2+, α-ketoglutarate, O2 and the peptide substrate to the enzyme in this order, and an ordered release of the hydroxylated peptide, CO2, succinate and Fe2+, in which Fe2+ need not leave the enzyme during each catalytic cycle and in which the order of release of the hydroxylated peptide and CO2 is uncertain. Ascorbate probably reacts by a substitution mechanism, either after the release of the hydroxylated peptide, CO2 and succinate or after the release of all products, including Fe2+, and dehydroascorbate is released before the binding of Fe2+. It is suggested that the ascorbate reaction is required to reduce either the enzyme-iron complex or the free enzyme, which may be oxidized by a side-reaction during some catalytic cycles, but not the majority. The mechanisms of the prolyl 4-hydroxylase and lysyl hydroxylase reactions are suggested to be identical.Zn2+, several citric acid cycle intermediates, nitroblue tetrazolium and homogentisic acid inhibited lysyl hydroxylase competitively with regard to Fe2+, α-ketoglutarate, O2 and ascorbate respectively, and epinephrine noncompetitively with regard to all cosubstrates. Apparent Ki values are given for the product and other inhibitors. 相似文献
17.
Christine C. Winterbourn Harry C. Button 《Archives of biochemistry and biophysics》1984,235(1):116-126
The ability of paraquat radicals (PQ+.) generated by xanthine oxidase and glutathione reductase to give H2O2-dependent hydroxyl radical production was investigated. Under anaerobic conditions, paraquat radicals from each source caused chain oxidation of formate to CO2, and oxidation of deoxyribose to thiobarbituric acid-reactive products that was inhibited by hydroxyl radical scavengers. This is in accordance with the following mechanism derived for radicals generated by γ-irradiation [H. C. Sutton and C. C. Winterbourn (1984) Arch. Biochem. Biophys.235, 106–115] PQ+. + Fe3+ (chelate) → Fe2+ (chelate) + PQ++ H2O2 + Fe2+ (chelate) → Fe3+ (chelate) + OH? + OH.. Iron-(EDTA) and iron-(diethylenetriaminepentaacetic acid) (DTPA) were good catalysts of the reaction; iron complexed with desferrioxamine or transferrin was not. Extremely low concentrations of iron (0.03 μm) gave near-maximum yields of hydroxyl radicals. In the absence of added chelator, no formate oxidation occurred. Paraquat radicals generated from xanthine oxidase (but not by the other methods) caused H2O2-dependent deoxyribose oxidation. However, inhibition by scavengers was much less than expected for a reaction of hydroxyl radicals, and this deoxyribose oxidation with xanthine oxidase does not appear to be mediated by free hydroxyl radicals. With O2 present, no hydroxyl radical production from H2O2 and paraquat radicals generated by radiation was detected. However, with paraquat radicals continuously generated by either enzyme, oxidation of both formate and deoxyribose was measured. Product yields decreased with increasing O2 concentration and increased with increasing iron(DTPA). These results imply a major difference in reactivity between free and enzymatically generated paraquat radicals, and suggest that the latter could react as an enzyme-paraquat radical complex, for which the relative rate of reaction with Fe3+ (chelate) compared with O2 is greater than is the case with free paraquat radicals. 相似文献
18.
《Journal of Molecular Catalysis .B, Enzymatic》2010,62(3-4):208-215
A novel and efficient immobilization of β-d-galactosidase from Aspergillus oryzae has been developed by using magnetic Fe3O4–chitosan (Fe3O4–CS) nanoparticles as support. The magnetic Fe3O4–CS nanoparticles were prepared by electrostatic adsorption of chitosan onto the surface of Fe3O4 nanoparticles made through co-precipitation of Fe2+ and Fe3+. The resultant material was characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. β-d-Galactosidase was covalently immobilized onto the nanocomposites using glutaraldehyde as activating agent. The immobilization process was optimized by examining immobilized time, cross-linking time, enzyme concentration, glutaraldehyde concentration, the initial pH values of glutaraldehyde and the enzyme solution. As a result, the immobilized enzyme presented a higher storage, pH and thermal stability than the soluble enzyme. Galactooligosaccharide was formed with lactose as substrate by using the immobilized enzyme as biocatalyst, and a maximum yield of 15.5% (w/v) was achieved when about 50% lactose was hydrolyzed. Hence, the magnetic Fe3O4–chitosan nanoparticles are proved to be an effective support for the immobilization of β-d-galactosidase. 相似文献
19.
Mechanisms of Saccharomyces Cerevisiae PMA1 H+-ATPase inactivation by Fe2+, H2O2 and Fenton reagents
Although considerably more oxidation-resistant than other P-type ATPases, the yeast PMA1 H+-ATPase of Saccharomyces cerevisiae SY4 secretory vesicles was inactivated by H2O2, Fe2+, Fe- and Cu-Fenton reagents. Inactivation by Fe2+ required the presence of oxygen and hence involved auto-oxidation of Fe2+ to Fe3+. The highest Fe2- (100 μM) and H2O2 (100 mM) concentrations used produced about the same effect. Inactivation by the Fenton reagent depended more on Fe2+ content than on H2O2 concentration, occurred only when Fe2+ was added to the vesicles first and was only slightly reduced by scavengers (mannitol, Tris, NaN3, DMSO) and by chelators (EDTA, EGTA, DTPA, BPDs, bipyridine, 1, 10-phenanthroline). Inactivation by Fe- and Cu- Fenton reagent was the same; the identical inactivation pattern found for both reagents under anaerobic conditions showed that both reagents act via OH·. The lipid peroxidation blocker BHT prevented Fenton-induced rise in lipid peroxidation in both whole cells and in isolated membrane lipids but did not protect the H+-ATPase in secretory vesicles against inactivation. ATP partially protected the enzyme against peroxide and the Fenton reagent in a way resembling the protection it afforded against SH-specific agents. The results indicate that Fe2+ and the Fenton reagent act via metal-catalyzed oxidation at specific metal-binding sites, very probably SH-containing amino acid residues. Deferrioxamine, which prevents the redox cycling of Fe2+, blocked H+-ATPase inactivation by Fe2+ and the Fenton reagent but not that caused by H2O2, which therefore seems to involve a direct non-radical attack. Fe-Fenton reagent caused fragmentation of the H+-ATPase molecule, which, in Western blots, did not give rise to defined fragments bands but merely to smears. 相似文献
20.
The efficiency of phenol degradation via Fenton reaction using mixture of heterogeneous goethite catalyst with homogeneous ferrous ion was analyzed as a function of three independent variables, initial concentration of phenol (60 to 100 mg /L), weight ratio of initial concentration of phenol to that of H2O2 (1: 6 to 1: 14) and, weight ratio of initial concentration of goethite catalyst to that of H2O2 (1: 0.3 to 1: 0.7). More than 90 % of phenol removal and more than 40% of TOC removal were achieved within 60 minutes of reaction. Two separate models were developed using artificial neural networks to predict degradation percentage by a combination of Fe3+ and Fe2+ catalyst. Five operational parameters were employed as inputs while phenol degradation and TOC removal were considered as outputs of the developed models. Satisfactory agreement was observed between testing data and the predicted values (R2
Phenol = 0.9214 and R2TOC= 0.9082). 相似文献