摘要:

AbstractThe kinetic behavior of yeast alcohol dehydrogenase (YADH) in sodium di‐2‐ethylhexylsulfosuccinate (AOT) isooctane reverse micelles has been studied using methyl ethyl ketone (MEK), NADH and Tris as the substrate, coenzyme and buffer, respectively. The solubility diagrams of aqueous buffer in the isooctane solution of AOT were established as a function of temperature and molar ratio of water of surfactant (ω0) at various Tris and AOT concentrations. The dependence of enzyme activity on enzyme concentration, pH, ω0and Tris concentration was determined. The optimal ω0was at 10–15, increasing slightly with an increase in Tris concentration. The YADH entrapped in reverse micelles exhibited minimum activity at a Tris concentration of 0·1 mol dm−3, while in aqueous buffer enzyme activity was not significantly affected by Tris concentration. Comparing the rate equation of the reduction of MEK by YADH in reverse micelles with that in aqueous buffer, the association of YADH and NADH could apparently have proceeded with an irreversible reaction before the substrate was bound, when performed in a reverse micellar system. Although the YADH entrapped in reverse micelles was less stable than when dissolved in aqueous buffer, the enzyme retained at least 20% activity after 21 h at 25°C and ω0= 20. This result was an improvement over previously

ISSN:0268-2575    

DOI:10.1002/jctb.280640302

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractOxidation of kraft black liquor with 14·39% solids content, obtained by cooking ofPinus pinasterwood, was studied by three different process; chemical oxidation with molecular oxygen at 120–138°C (oxygen partial pressure ≈ 0·15 MPa); biological (enzymatic) oxidation; and combined oxidation (in the sequence: chemical + enzymatic). Lignin degradation was followed by high pressure liquid chromatography (HPLC). Production of low molecular weight compounds, e.g. vanillin, was monitored by gas chromatography (GC). Chemical oxidation produced about 1.5 g of vanillin per dm3of liquor (0·904 g per 100 g of solids). Biodegradation products had molecular weights near to that of vanillin and mainly around 100 daltons, but vanillin was not detected. In the combined oxidation process, vanillin was consumed with a concomitant reduction of the HP

ISSN:0268-2575    

DOI:10.1002/jctb.280640303

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstractβ‐Methylpentadecanedioic acid dimethyl ester (I) was synthesized electrochemically by Kolbe reaction using β‐methylglutaric acid monomethyl ester (II) and α,ω‐dodecanedioic acid monomethyl ester (III) as starting materials in MeOH solution. Electrolysis was carried out ofr about 4–5 h, when solution pH ≥ 7, followed by extraction with petroleum ether and distillation to obtain a colourless oily product (I) The minimum production cost occurred when the mole ration ofIItoIIIwas 1:1·38 and unreactedIIIcould be recovered. The product synthesized (I) completely met the requirement of artificially sy

ISSN:0268-2575    

DOI:10.1002/jctb.280640304

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe concentration of reactants at an interface cannot be determined directly. The concentration at the interface has been estimated by measuring the interfacial tension at the interface between two immiscible solutions. An aqueous phase, de‐ionised water containing penicillin G, and an organic phase containing amberlite LA‐2 were used as a typical system to study the kinetics of interfacial reaction. The interfacial tension was measured by a spinning‐drop tensiometer at 25 ± 0·1°C. The interfacial tension was found to correlate well with the concentrations of penicillin G, Amberlite, LA‐2 and proton in each respec

ISSN:0268-2575    

DOI:10.1002/jctb.280640305

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe rate constant and activation energy of liquid‐phase oxidation catalyzed by CuSO4· 5h2O, and Co2O3, were found for synthesized wastewaters containing 1000 mg dm−3phenol and 1500 dm−3p‐chlorophenol, respectively. Among the catalysts, CuSO4· 5H2O was demonstrated to be the most effective in reducing the concentration of phenols in wastewaters. The effects of oxygen flow rates and temperatures on the oxidation efficiency were also discussed. The analysis of total organic carbon on the end products after oxidations showed that the liquid phase contained only 10% of intermediate products. Oxidation at different pH values suggested that phenols could be favourably destroyed in an alkali

ISSN:0268-2575    

DOI:10.1002/jctb.280640306

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractDynamic two‐dimensional modelling was used in a theoretical analysis of the overheating problem in solid‐state fermentation within a packed‐bed bioreactor. The model described the growth and death of the fungusRhizopus oligosporusas functions of temperature; the generation of metabolic heat; and the transfer of heat within the packed‐bed by conduction and convection. The model predicted that convection was the dominant heat transfer mechanism under the design and operational parameters applied. Significant death occurred in the upper region of the bed where the highest temperatures were reached. The temperature rise at the top of the bed could be minimized by using high superficial air velocities or low inlet air temperatures. The most effective strategy for a column with a bed height: bed diameter ratio of 1:1 or less was to use a high superficial air v

ISSN:0268-2575    

DOI:10.1002/jctb.280640307

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe adsorption of sodium benzoate, 2,4‐dichlorophenol and 2,4,6‐trichlorophenol onto five activated carbons made from Northern Ireland lignite is reported. A Two‐stage process consisting of chemical activation during the charring of the lignite, followed by steam activation was used to produce the activated carbons. The adsorption equilibrium isotherms obtained for the carbons have been plotted to obtain the Freundlich, Langmuir and Redlich Peterson constants. Chemical and steam activation methods both produced improvements to the carbon performance on their own, with the combination of the two treatments providing the best results. In the main the chemical treatment providing the best improvement on its own also gave the biggest improvement when combined with steam treatment. BET surface area measurements made using nitrogen adsorption correlate strongly with the capacity for benzoate adsor

ISSN:0268-2575    

DOI:10.1002/jctb.280640308

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe structural changes of the regenerated silk fibroin membranes for immobilizing glucose oxidase were characterized with FT‐IR spectra. The results of electronic absorption spectra and scanning electron microscopy illustrated that the glucose oxidase in the membranes existed in aggregates. The blend membranes exhibited an island‐like structure, attributable to the incompatible and weak intermolecular interactions between regenerated silk fibroin and glucose oxidase. The glucose sensor was constructed by combining glucose oxidase immobilized in regenerated silk fibroin membrane with an Eastman‐AQ‐ferrocene modified electrode. The advantages of the mediator include high stability and the ability to use a less positive potential for increased sele

ISSN:0268-2575    

DOI:10.1002/jctb.280640309

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAromatic extract residues, as by‐products, are accumulated in local refineries through the refining of lubricating oils. These residues are dealt with as low economic value products, even their disposal imposes serious problems to the refineries. Therefore, the present work is aimed at upgrading these residues by using them to synthesis some different petroleum additives, e. g. antioxidants, ashless dispersant additives, pour point depressants and flow improvers for crankcase lubricating oils and fuels. Antioxidants are synthesised by reacting mono‐aromatics with phosphorus pentasulphide (P2S5) in the presence of zince oxide (ZnO). Ashless dispersant additives are synthesised by reacting alkylated mono‐aromatics (using chlorinated paraffin wax as alkylating agent) with formaldehyde solution (37%) in the presence of polyisobutylene succinimide. Pour point depressants and flow improvers are synthesised by acylating di‐aromatics via a Friedel‐Crafts' reaction. Comparative evaluation of the performance of the synthesised products with commercial additives showed their good e

ISSN:0268-2575    

DOI:10.1002/jctb.280640310

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe separation behavior of phenylacetic acid (PAA), 6‐aminopenicillanic acid (6‐APA) and penicillin‐G (Pen‐G) with electrodialysis under constant current was studied. The effects of ionic concentrations and current density on their separation behavior were investigated. The sorption of PAA, 6‐APA and Pen‐G and in the anion exchange membrane, and the variations of the applied voltage and current efficiencies with time during electrodialysis were also examined. It was found that the molecular size and the affinity toward the anion exchange membrane played a key role for the electrodialysis of PAA, 6‐APA and Pen‐G. Phenylacetic acid had the lowest affinity toward the membrane but the fastest transport rate. Penicillin‐G had the highest affinity toward the membrane but the slowest transport rate. With the increase of Pen‐G concentration, the concentration polarization of Pen‐G in the vicinity of anion exchange membrane became very serious, which severely retarded the transport of PAA and 6‐APA. Although the increase of current density accelerated the transport of PAA, 6‐APA and Pen‐G, more serious concentration polarization of Pen‐G occurred and the separation ra

ISSN:0268-2575    

DOI:10.1002/jctb.280640311

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY