摘要:

AbstractAdsorption of cells on particulate carriers is potentially one of the most cost‐effective immobilization techniques available. Diatomite carriers, such as Celite, have desirable physical properties, are inexpensive, and are suitable for both mycelial and bacterial systems. This work investigated the use of diatomite carriers as a biocatalyst support in a packed‐bed reactor whereL‐tyrosine was enzymatically decarboxylated using adsorbed, non‐growing cells ofStreptococcus faecalis. Composition of microbial adsorption on different Celite types, with mean pore sizes ranging from 0.55 to 22 μm, showed there was no significant difference in biomass loading capacity under the conditions used. Using Celite 560, biomass loadings in a packed‐bed reactor varied from 10 to 30 g dm−3of reactor volume, which compares favourably with other adsorption methods. When used to decarboxylateL‐tyrosine, the reactor was found to have a half‐life of 15–20 h. A combination of enzyme activity loss and slow leakage of biomass from the packed‐bed reactor was responsible for the decline in conversion. Treatment of theS. faecaliscells with glutaraldehyde significantly reduced the enzyme activity loss and extended the reactor half‐life to 65 h, but had little effect on the rate of cell leakage from the reactor. Further work on reduction of cell leakage rate seems necessary for evaluation of the

ISSN:0268-2575    

DOI:10.1002/jctb.280470202

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe elimination of Cr(VI) from aqueous solutions at neutral and low alkaline pH by photocatalytic reduction to Cr(III), using ZnO powder as catalyst, is investigated. The study has been performed by determination of the percentage of Cr(VI) eliminated in the presence of some species (i.e. Zn(II), Cd(II), Ni(II), Ca(II), CH3COO−, PO3‐4, CO2‐3, S2‐and NH3) which usually are found in wastes together with Cr(VI). The results obtained show that the presence of some species prevents the alkalinization of the solution during irradiation, which increases the yield of Cr(VI) photoreduction. Other species, such as S2‐and NH3, are oxidized during illumination: thus they prevent electron–hole recombination and, consequently, increase the yield of the Cr(VI)

ISSN:0268-2575    

DOI:10.1002/jctb.280470203

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA sensor for NH+4ions has been developed, which consists of immobilized micro‐organisms (Bacillus subtilis, Pseudomonas aeruginosa, Trichosporon cutaneum) in combination with an electrochemical transducer. This sensor is based on the measurement of acceleration of respiration after addition of NH+4in the presence of glucose. The physiological background of this signal and its connection with NH+4ion uptake and/or metabolism is discussed.The response time of the sensor is about 5.10 s for NH+4ions. A linearity was observed between 0.005 and 0.15 mmol dm−3NH+4ions. The sensitivity of the sensor remained almost constant for 12 days. The sensor was used to determine NH+4ions in a microbial fermentation br

ISSN:0268-2575    

DOI:10.1002/jctb.280470204

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractSaccharomyces cerevisiaeATCC 36859 preferentially consumes glucose from glucose–fructose mixtures. Synthetic media and complex media containing high fructose corn syrup supplemented with Jerusalem artichoke juice were used for the production of pure fructose syrup by the conversion of glucose to ethanol. Fructose was not converted in these processes. Increasing the concentration of Jerusalem artichoke juice increased the yields of ethanol and biomass and decreased the process time. A similar effect was obtained at a low juice concentration when a larger amount of biomass was used for the inoculum. The product from this process contained only fructose and ethanol. Use of food‐grade materials results in a pure fructose syrup that is suitable for human consumpt

ISSN:0268-2575    

DOI:10.1002/jctb.280470205

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractOslefins and diolefins are important intermediates in the petrochemical industry and the future promises a further substantial increase in demand. While several catalysts have been formulated in the past for the abstraction of hydrogen from butenes and propylene, these catalysts are inefficient in the abstraction of first hydrogen from butane. Bismuth molybdates (β and γ‐phases) containing iron oxide and supported on alumina are used as catalysts in the present investigation on the oxidative dehydrogenation ofn‐butane. Effects of catalyst content, temperature and oxygen:n‐butane ratio on conversion and selectivity to butadiene and (C4H8+ C4H6) are studied in the following ranges of experimental conditions: β‐bismuth molybdate/100 mol support I(K), 3–9; γ‐bismuth molybdate/100 mol support I(K), 5‐20; temperature, 400–500°C; O2: b

ISSN:0268-2575    

DOI:10.1002/jctb.280470206

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

Abstract9,10‐Dibromoanthracene (2) obtained from anthracene by bromination was reacted with cuprous cyanide in refluxing DMF to obtain 9,10‐dicyanoanthracene (3). The key intermediate (3) was condensed with orthophenylenediamine (4a),ortho‐aminophenol (4b) and dicyanodiamine (6) to give 9,10‐bis(benzimidazol‐2‐yl)anthracene (5a), 9,10‐bis(benzoxazol‐2‐yl)anthracene (5b) and 9,10‐bis(4,6‐diamino‐S‐triazin‐2‐yl)anthracene (5c), respectively. The spectral properties of5a‐5cwere studied. These compounds, when applied as disperse dyes on polyester

ISSN:0268-2575    

DOI:10.1002/jctb.280470207

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractNickel–tungsten‐based hydrotreating catalysts have been prepared with different metals impregnation profiles and tested for the hydrodesulphurisation, hydrodenitrogenation and hydrogenation of model compounds. Penetration of the catalyst by the model compounds depends on the pore structure of the support and determines activity. Best performance is associated with optimal Ni:W ratios dished across the active region of the catalyst rather than with an even impregnation across all of the supp

ISSN:0268-2575    

DOI:10.1002/jctb.280470208

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe kinetics of maleic acid hydroxylation by H2O2in the presence of a homogeneous catalyst have been studied. A rate equation for the consumption of H2O2has been obtained. The retardation of the reaction resulting from catalyst deactivation was observed. The fall in the activity of catalyst during the course of the reaction has been associated with the formation of a complex between the former and the reaction product.

ISSN:0268-2575    

DOI:10.1002/jctb.280470209

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractGlucoamylase and glucose isomerase, which are often used in industry to produce high‐fructose corn syrup, were immobilized on porous anilino‐sulfonic polystyrene beads and porous triethanolamine methyl polystyrene beads, respectively. These charged supports altered the pH profiles of the two enzymes such that it was possible to carry out simultaneous saccharification and isomerization at pH 6.5 or pH 7.5 using immobilized glucoamylase and immobilized glucose isomerase. This process is very difficult to accomplish with soluble glucoamylase and glucose isomerase because of the large difference in the pH profiles of the two enzymes in their soluble f

ISSN:0268-2575    

DOI:10.1002/jctb.280470210

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

ISSN:0268-2575    

DOI:10.1002/jctb.280470211

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY