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1.
Ingrid Persson Folke Tjerneld Bärbel Hähn-Hagerdal 《Applied biochemistry and biotechnology》1991,27(1):9-25
Cellulolytic enzyme production in aqueous two-phase systems withTrichoderma reesei Rutgers C30 has been investigated. The influ ence of different phase systems, as well as addition of media compo nents and substrate on enzyme production have been studied. Extractive enzyme production in fed-batch cultivations was per formed in a phase system composed of PEG 8000 5%-Dextran T500 7% with 1% Solka-Floc BW 200 as substrate. The cellulolytic enzyme system was intermittently withdrawn with the top phase. Addition of media components every 24 h and cellulose every 72 h gave an aver age enzyme activity in the withdrawn top phase of 2.2 FPU/mL dur ing 170 h cultivation. The corresponding productivity was 18 FPU/lh. The productivity was increased to 24 FPU/l.h when media compo nents and cellulose were added every 72 h. The average enzyme con centration was then 1.6 FPU/mL. The results are discussed in relation to methods for cellulolytic enzyme production involving immobiliza tion and cell recycling. 相似文献
2.
In order to decide whether Alizarin Fluorine Blue (alizarin complexan, 3-amino-methylalizarin-N,N-diacetic acid) is a suitable reagent for the spectrophotometric determination of aluminium, values of the stability constants for some reactions of this reagent with aluminium(III) and iron(III) have been determined spectrophotometrically in a medium containing 20 % dioxan and 80 % water at ionic strength 0.1. The values of the constants that were determined are log K(Al)(AlHL) = 14.3, log K(2Al)(Al2L) = 25.3 and log K(Fe)(FeHL) = 19.6. These results were employed in the design of a method for the spectrophotometric determination of aluminium in the presence of iron and titanium. The Sandell sensitivity is 0.01 mug/cm(2) and the coefficient of variation for 34 determinations was 0.9 %. 相似文献
3.
József Medve Jerry Ståhlberg Folke Tjerneld 《Applied biochemistry and biotechnology》1997,66(1):39-56
Adsorption to microcrystalline cellulose (Avicel) of pure cellobiohydrolase I and II (CBH I and CBH II) fromTrichoderma reesei has been studied. Adsorption isotherms of the enzymes were measured at 4‡C using CBH I and CBH II alone and in reconstituted
equimolar mixtures. Several models (Langmuir, Freundlich, Temkin, Jovanovic) were tested to describe the experimental adsorption
isotherms. The isotherms did not follow the basic (one site) Langmuir equation that has often been used to describe adsorption
isotherms of cellulases; correlation coefficients (R2) were only 0.926 and 0.947, for CBH I and II, respectively. The experimental isotherms were best described by a model of
Langmuir type with two adsorption sites and by a combined Langmuir-Freundlich model (analogous to the Hill equation); using
these models the correlation coefficients were in most cases higher than 0.995. Apparent binding parameters derived from the
two sites Langmuir model indicated stronger binding of CBH II compared to CBH I; the distribution coefficients were 20.7 and
3.7 L/g for the two enzymes, respectively. The binding capacity, on the other hand, was higher for CBH I, 1.0 Μmol (67 mg)
per gram Avicel, compared to 0.57 Μmol/g (30 mg/g) for CBH II. The isotherms when analyzed with the combined Langmuir-Freundlich
model indicated presence of unequal binding sites on cellulose and/or negative cooperativity in the binding of the enzyme
molecules. 相似文献
4.
The complexation reaction between Alizarin complexan ([3-N,N-di(carboxymethyl)aminomethyl]-1,2-dihydroxyanthraquinone; H(4)L) and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II) has been studied by a spectrophotometric method. All these metal ions form 1:1 complexes with HL; 2:1 metal:ligand complex were found only for Pb(II) and Cu(II). The stability constants are (ionic strength I = 0.1, 20 degrees C): Zn(2+) + HL(3-) right harpoon over left harpoon ZnHL(-) log K +/- 3sigma(log K) = 12.19 +/- 0.09 (I = 0.5) Ni(2+) + HL(3-) right harpoon over left harpoon NiHL(-) log K +/- 3sigma(log K) = 12.23 +/- 0.21 Pb(2+) + HL(3-) right harpoon over left harpoon PbHL(-) log K +/- 3sigma(log K) = 11.69 +/- 0.06 PbHL(-) + Pb(2+) right harpoon over left harpoon Pb(2)L + H(+) log K approximately -0.8 Co(2+) + HL(3-) right harpoon over left harpoon CoHL(-) log K 3sigma(log K) = 12.25 + 0.13 Cu(2+) + HL(3-) right harpoon over left harpoon CuHL(-) log K 3sigma(log K) = 14.75 +/- 0.07 Cu(2+) + CuHL(-) right harpoon over left harpoon Cu(2)L + H(+) log K approximately 3.5 The solubility and stability of both the reagent and the complexes and the closenes of the values of the stability constants make this reagent suitable for the photometric detection of several metal ions in the eluate from an ion-exchange column. 相似文献
5.
It is commonly observed that the rate of enzymatic hydrolysis of solid cellulose substrates declines markedly with time. In
this work the mechanism behind the rate reduction was investigated using two dominant cellulases of Trichoderma reesei: exoglucanase Cel7A (formerly known as CBHI) and endoglucanase Cel7B (formerly EGI). Hydrolysis of steam-pretreated spruce
(SPS) was performed with Cel7A and Cel7B alone, and in reconstituted mixtures. Throughout the 48-h hydrolysis, soluble products,
hydrolysis rates, and enzyme adsorption to the substrate were measured. The hydrolysis rate for both enzymes decreases rapidly
with hydrolysis time. Both enzymes adsorbed rapidly to the substrate during hydrolysis. Cel7A and Cel7B cooperate synergistically,
and synergism was approximately constant during the SPS hydrolysis. Thermal instability of the enzymes and product inhibition
was not the main cause of reduced hydrolysis rates. Adding fresh substrate to substrate previously hydrolyzed for 24 h with
Cel7A slightly increased the hydrolysis of SPS; however, the rate increased even more by adding fresh Cel7A. This suggests
that enzymes become inactivated while adsorbed to the substrate and that unproductive binding is the main cause of hydrolysis
rate reduction. The strongest increase in hydrolysis rate was achieved by adding Cel7B. An improved model is proposed that
extends the standard endo-exo synergy model and explains the rapid decrease in hydrolysis rate. It appears that the processive
action of Cel7A becomes hindered by obstacles in the lignocellulose substrate. Obstacles created by disordered cellulose chains
can be removed by the endo activity of Cel7B, which explains some of the observed synergism between Cel7A and Cel7B. The improved
model is supported by adsorption studies during hydrolysis. 相似文献
6.
V. V. Matveev D. A. Markelov V. I. Chizhik P. Ingman E. Lähderanta 《Russian Chemical Bulletin》2013,62(9):1985-1990
1-Ethyl-3-methylimidazolium acetate was studied by NMR relaxation. The temperature dependences of the spin-lattice relaxation rates (1/T 1) for 1H and 13C were obtained. The curves with maxima were observed for the majority of the temperature dependences 1/T 1, which provided a reliable temperature dependence of the correlation times (τc). In the low-temperature range, the proton relaxation rates tend to an asymptotic value, which is related, most likely, to spin diffusion manifested in the studied samples. The values of correlation times τc calculated for 1H and 13C of the same functional group almost coincide at high temperatures, which confirms that the used approach is adequate for the determination of characteristic times of rotational reorientation of counterions in the studied ionic liquid. 相似文献
7.
A method for the study of two-phase equilibria by extraction in liquid-liquid segmented flow is presented. The main advantage of the method is the very rapid equilibration achieved. In many cases a contact time of 5 sec is sufficient. By performing the measurements needed on-line with the extraction the total residence time of a substance studied in the system can be kept below 10 sec. This makes it possible to study two-phase equilibria of moderately unstable compounds. Other advantages are the semi-enclosed design, which minimizes contact with solvent fumes and increases the speed of operation after the system has been set up. The system has been used for a study of the two-phase equilibria of dithiocarbamic acids. The dithiocarbamates are often used for the separation and preconcentration of metals, and co-extraction of the reagent can cause severe interference in the final determination. By means of the extraction constants presented, the extraction of diethyldithiocarbamic acid and pyrrolidine-dithiocarbamic acid into Freon 113, carbon tetrachloride, methyl isobutyl ketone and chloroform can be estimated. 相似文献
8.
Kepka C Rhodin J Lemmens R Tjerneld F Gustavsson PE 《Journal of chromatography. A》2004,1024(1-2):95-104
The primary purification of a 6.1 kilo base pair (kbp) plasmid from a desalted alkaline lysate has been accomplished by a thermoseparating aqueous two-phase system [(50% ethylene oxide-50% propylene oxide)-Dextran T 500]. The partitioning of the different nucleic acids (plasmid DNA, RNA, genomic DNA) in the thermoseparating aqueous two-phase system was followed both qualitatively by agarose gel electrophoresis and quantitatively by analytical chromatography (size exclusion- and anion-exchange mode) and PicoGreen fluorescence analysis. The experimental results showed a complete recovery of the plasmid DNA to the top phase, while 80% of total RNA and 58% of total protein was discarded to the bottom phase. Moreover, a 3.8-fold volume reduction of the plasmid DNA solution was achieved. By using a final thermoseparating step, the EO50PO50 polymer could be efficiently recycled, resulting in plasmid solution containing less than 1% polymer. The developed thermoseparating aqueous two-phase system shows great potential for the large-scale processing of plasmid DNA. 相似文献
9.
The segmentation of two immiscible solvents in a continuous liquid—liquid extraction flow system has been studied with a computer-controlled photometric detection system (resolution time 3 msec). The T-shaped segmentors tested were made of fluoroplastic, glass (A4-T fitting) and a modified glass (A8-T fitting). The modified A8-T fitting gave the most repeatable segmentation (rsd 2%). 相似文献
10.