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1.
Leda M. F. Gottschalk Jacyara M. B. Macedo Elba P. S. Bon 《Applied biochemistry and biotechnology》1999,79(1-3):771-778
Lignin peroxidase (LiP) production cost should be reduced to justify its use in the control of environmental pollution. In
this work, we studied the enzyme production by Streptomyces viridosporus T7A using glucose or corn oil as a carbon source having 0.65% yeast extract as a nitrogen source. Enzyme activity, observed
using either 0.65% glucose or corn oil at 0.1, 0.5, and 1.0% concentration, was 300, 150, 300, and 200 U/L, respectively.
Although higher enzyme activity was obtained in both media containing 0.65% glucose and 0.5% corn oil, the use of corn oil
resulted in a better LiP stability. When combined carbon sources were used, higher values of enzyme activity (360, 350, and
225 U/L) were observed in media with 0.65% glucose and supplemented with 0.1, 0.5, and 1.0% corn oil, respectively. Although
the presence of both glucose and 0.5% corn oil is favorable for LiP production, satisfactory results in terms of enzyme production
and stability could be also observed using 0.5% corn oil as a sole carbon source, which may lead to reduced production costs
of the LiP enzyme. 相似文献
2.
Leda M. F. Gottschalk Ronaldo Nobrega Elba P. S. Bon 《Applied biochemistry and biotechnology》2003,108(1-3):799-807
The effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A was studied in a bench-scale bioreactor using a previously optimized growth medium (0.65% yeast extract and 0.1% corn
oil, pH7.0) at 37°C and natural pH. Airflow rates of 0.3, 1.0, and 1.5 vvm and a fixed agitation of 200 rpm were initially
studied followed by 1.0 vvm and 200, 300, 400, and 500 rpm. The use of 1.0 vvm and 400 rpm increased enzyme concentration
1.8-fold (100–180 U/L) and process productivity 4.8-fold (1.4–6.7 U/[L·h]) in comparison with the use of 200 rpm and 0.3 vvm.
The inexpensive corn oil, used as carbon source, besides its antifoam properties, proved to be nonrepressive for enzyme production. 相似文献
3.
It is well known that lignin degradation is a key step in the natural process of biomass decay whereby oxidative enzymes such
as laccases and high redox potential ligninolytic peroxidases and oxidases play a central role. More recently, the importance
of these enzymes has increased because of their prospective industrial use for the degradation of the biomass lignin to increase
the accessibility of the cellulose and hemicellulose moieties to be used as renewable material for the production of fuels
and chemicals. These biocatalysts also present potential application on environmental biocatalysis for the degradation of
xenobiotics and recalcitrant pollutants. However, the cost for these enzymes production, separation, and concentration must
be low to permit its industrial use. This work studied the concentration of lignin peroxidase (LiP), produced by Streptomyces viridosporus T7A, by ultrafiltration, in a laboratory-stirred cell, loaded with polysulfone (PS) or cellulose acetate (CA) membranes with
molecular weight cutoffs (MWCO) of 10, 20, and 50 KDa. Experiments were carried out at 25 °C and pH 7.0 in accordance to the
enzyme stability profile. The best process conditions and enzyme yield were obtained using a PS membrane with 10 KDa MWCO,
whereby it was observed a tenfold LiP activity increase, reaching 1,000 U/L and 90% enzyme activity upholding. 相似文献
4.
The production of lignin peroxidase byStreptomyces viridosporus T7A was studied in shake flasks and under aerobic conditions in a 7.5-L batch fermentor. Lignin peroxidase synthesis was found to be strongly affected by catabolite repression. Lignin peroxidase was a non-growth-associated, secondary metabolite. The maximum lignin peroxidase activity was 0.064 U/mL at 36 h.
In order to maximize lignin peroxidase activity, optimal conditions were determined. The optimal incubation temperature, pH, and substrate (2,4-dichlorophenol) concentration for the enzyme assays were 45°C, 6, and 3 mM, respectively. Stability of lignin peroxidase was determined at 37, 45, and 60°C, and over the pH range 4–9.
相似文献5.
Streptomyces viridosporus produces an intracellular aromatic aldehyde oxidase that oxidizes aromatic and α, β-unsaturated aromatic aldehydes to their
corresponding acids. It also produces extracellular oxidase as shown by zones of clearing when grown on agar containing insoluble
dehydrodivanillin (DHDV). This extracellular form may be responsible for oxidizing aldehyde groups in lignin. The extracellular
oxidase was expressed maximally after 3 d growth in medium containing only yeast extract. However, higher levels were produced
when lignocellulose was in the medium. The enzyme was partially purified and its molecular weight was approximated to be about
80,000 daltons. Mutant cultures that had lost the ability to produce zones of clearing on DHDV-containing agar solubilized
smaller quantities of lignin as compared to the wild type, except for one strain. A partially purified oxidase preparation
was shown to oxidize a natural lignocellulose substrate. 相似文献
6.
7.
Zhaofeng Mao 《Journal of solid state chemistry》2007,180(2):453-460
The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 °C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO3 crystal obviously depends on the starting pH. CaCO3 crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {1 0 4} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624]. 相似文献
8.
Crystallization of calcium carbonate in magnetic water in the presence of paramagnetic substances 总被引:1,自引:0,他引:1
V. V. Goncharuk V. A. Bagrii R. D. Chebotareva S. Yu. Bashtan A. V. Nanieva 《Russian Journal of Applied Chemistry》2008,81(12):2108-2111
Effect of a paramagnetic substance on the crystallization of calcium carbonate in magnetic water was studied. 相似文献
9.
In this paper, a systematic study of the influence of various experimental parameters on the morphology and size of CaCO3 crystals after room-temperature crystallization from water in the presence of poly(ethylene glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) is presented. The pH of the solution, the block copolymer concentration, and the ratio [polymer]/[CaCO3] turned out to be important parameters for the morphogenesis of CaCO3, whereas a moderate increase of the ionic strength (0.016 M) had no influence. Depending on the experimental conditions, the crystal morphologies can be tuned from calcite rhombohedra via rods, ellipsoids or dumbbells to spheres. A morphology map is presented which allows the prediction of the crystal morphology from a combination of pH, and CaCO3 and polymer concentration. Morphologies reported in literature for the same system but under different crystallization conditions agree well with the predictions from the morphology map. A closer examination of the growth of polycrystalline macroscopic CaCO3 spheres by TEM and time-resolved dynamic light scattering showed that CaCO3 macrocrystals are formed from strings of aggregated amorphous nanoparticles and then recrystallize as dumbbell-shaped or spherical calcite macrocrystal. 相似文献
10.
11.
The well-defined structure of lipid A-diphosphate in aqueous solutions provides a way of observing the formation of calcium carbonate crystals. The crystals are either tetrahedral or rhombohedral calcite at a volume fraction of phi = 5.4 x 10 (-4) at pH 5.8 or the vaterite polymorph of CaCO(3) at a volume fraction of phi = 7.8 x 10 (-4) at pH 5.8. In both cases, nucleation, adsorption pH, and the shape-dependent template of lipid A-diphosphate control the formation of the calcite and vaterite. 相似文献
12.
In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO3). In the presence of high concentration of polyacrylic acid (PAA), the CaCO3 films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO3 films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH2 group, whereas, for those grown on chitosan with 80% DA the CaCO3 films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite. 相似文献
13.
A. Braileanu M. Zaharescu D. CriŞan D. FĂtu E. Segal C. Danciulescu 《Journal of Thermal Analysis and Calorimetry》1996,47(2):569-575
Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3.The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3. 相似文献
14.
Spectrophotometric determination of hydrogen peroxide by using the cleavage of Eriochrome black T in the presence of peroxidase 总被引:1,自引:0,他引:1
A new hydrogen donor for peroxidase, Eriochrome black T, was reported for the first time. Steady-state catalytic velocity depends upon enzyme and substrate concentrations, and a Michaelis-Menten K(m) value of 1.72x10(-5) mol l(-1) and a V(max) value of 4.43x10(-3) s(-1) were measured at pH 8.6. Trace amount of hydrogen peroxide (2x10(-7)-1.0x10(-5) mol l(-1)) was determined in aqueous solution by using the cleavage of Eriochrome black T catalyzed by peroxidase. The method is simple and practical, with high sensitivity and enzymatic activity. 相似文献
15.
Bao Yong-zhong Zhang Li-feng Huang Zhi-ming Weng Zhi-xue 《European Polymer Journal》2003,39(5):1001-1006
The absorption of vinyl chloride (VC) on surface-treated light-grade and nano-scale calcium carbonate (CaCO3), and VC suspension polymerization in the presence of CaCO3 were carried out in a 5 L autoclave. It showed that the absorption of VC on CaCO3 increased with the partial pressure of VC up to a critical point. Nano-scale CaCO3 was more effective in absorbing VC than light-grade CaCO3 at the same temperature and partial pressure of VC due to its greater surface area. The absorption behavior of VC/CaCO3 follows Langmuir isothermal equation. In view of the absorption of VC on CaCO3, Xie’s model [J. Appl. Polym. Sci. 34 (1987) 1749] was modified to relate pressure, temperature, the amount of CaCO3 and conversion for VC suspension polymerization in the presence of CaCO3. The model simulation showed that VC conversions at the pressure drop point and at a certain pressure drop decreased with the increase of the amount of added CaCO3, and the influence of nano-scale CaCO3 was greater than that of light-grade CaCO3. The simulated VC conversions fitted well with that obtained from VC suspension polymerizations in the presence of different amounts of light-grade or nano-scale CaCO3. 相似文献
16.
Formation of CaO from thermal decomposition of calcium carbonate in the presence of carboxylic acids
Effect of 5% tartaric, succinic and citric acids on the decomposition of CaCO3 have been studied by TG-DSC and X-ray diffraction techniques. The decomposition temperature of CaCO3 is not decreased and at the same time particle size distribution and morphology of CaO are changed as determined by laser
granulometer and SEM studies. 相似文献
17.
J. Marín-Cruz R. Cabrera-Sierra M. A. Pech-Canul I. González 《Journal of Solid State Electrochemistry》2007,11(9):1245-1252
Electrochemical impedance spectroscopy (EIS) was used to assess the relative effects of scaling and corrosion for steel electrodes
in cooling water media and to obtain information on corrosion inhibition and scale inhibition properties of 1-hydroxyethylidene-1,1-diphosphonic
acid (HEDP) and hydroxyphosphonoacetic acid (HPA). Steel electrodes were preliminary scaled with CaCO3 in simulated cooling water and then immersed in the characterization solution. Analysis of the impedance spectra with a simple
model allowed following of the time evolution of physical parameters corresponding to the calcium carbonate islands and to
the corrosion products accumulated in areas not covered by the scale. In uninhibited solutions, the main effect was the progressive
deposit of corrosion products with no additional scaling and little restructuring of the initial carbonate islands. When the
solution contained HEDP alone, part of the initial scale was detached from the surface, but the presence of HPA or the mixture
HPA+HEDP only induced structural modifications of the initial scale. Moreover, the impedance analysis also showed that HPA
exhibited better corrosion inhibition properties than HEDP. 相似文献
18.
The kinetics of the carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate has been
studied by a thermogravimetric analyzer (TGA). An empirical rate expression of zinc yield has been determined from the experimental
data obtained. The dependencies of the rate of zinc yield on the operating variables was found to be less pronounced for the
Li2CO3 catalyzed system than those for uncatalyzed system. 相似文献
19.
Kurenkov V. F. Nadezhdin I. N. Hartan H. -G. Lobanov F. I. 《Russian Journal of Applied Chemistry》2009,82(2):328-332
Russian Journal of Applied Chemistry - Kinetic features of clarification of 1% suspension of calcium carbonate under the action of coagulants (aluminum sulfate, hydroxoaluminum chloride) and... 相似文献
20.
The influence of four calcium complexing additives, i.e., citric acid (CIT), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA) and pyromellitic acid (PMA), and their concentration on the induction time of calcium carbonate nucleation has been studied. The experiments were performed by rapidly mixing a sodium carbonate solution and a calcium chloride solution of various concentrations. The induction time was obtained by recording the white light absorption of the solution. Chemical speciation was used to estimate the initial thermodynamic driving force of each experiment. The induction time was found to increase with additive concentration. The effect varies from one additive to another. CIT causes the greatest increase in induction time and PMA the least. Using classical nucleation theory the experimental data were evaluated in terms of the interfacial energy. In pure water a value of 37.8 mJ m(-2) was obtained, showing good agreement with other works. CIT, DTPA and EDTA caused a notable increase of the interfacial energy at a concentration of 0.5 mmol l(-1). PMA does not appear to have any effect at all on the interfacial energy. Different mechanisms for the influence of the additives on the measured induction time and on the estimated interfacial energy are discussed. 相似文献