摘要:

AbstractFor gluconic acid fermentation with Aspergillus niger oxygen‐enriched air was used to increase dissolved oxygen concentration during the production phase from c. 30% to 100% saturation related to air at 1 bar. At the highest dissolved oxygen concentration the activity of glucose oxidase increased more than three‐fold. At the same time, the gluconic acid production rate increased by a factor of two. During the fermentations, glucose oxidase was present endocellularly as well as exocellularly; the presence of this enzyme in the broth was due to a controlled secretion. It was found that the two fractions of the enzyme showed different activities in their contribution to overall acid production. Due to a limitation of oxygen diffusion into the mycelial pellets, activity of endocellular enzyme was reduced by 50–80%. However, since the major part of the enzyme was present in the pellets the action of endocellular glucose oxidase is not negligible. This latter factor must be taken into consideration when optimizing bioreactor d

ISSN:0268-2575    

DOI:10.1002/jctb.280500102

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe catalytic conversion of methanol over new generation molecular sieve silicoaluminophosphate of type 5 (SAPO‐5) has been studied. The formation of gaseous, liquid and solid hydrocarbons have been observed. While the gaseous hydrocarbon contains 32·5–56·7 wt% of olefins, the liquid product comprises hydrocarbons in the boiling range 98°C‐320°C as determined by gas chromatographic distillation technique. The solid hydrocarbon was identified as hexamethylbenzene by physical, chemical and spectral

ISSN:0268-2575    

DOI:10.1002/jctb.280500103

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractOptimal feed temperature was determined for a nonisothermal immobilized enzymatic reaction with enzyme deactivation in a packed‐bed reactor. The optimal feed temperature was obtained by maximizing the average substrate conversion over a given reaction period. Simulation showed the optimal feed temperature to be strongly dependent on the flow dispersion, the reaction activation energy, the corresponding enzyme inactivation energy and the heat of reaction. It was also observed that in a plug flow reactor the enzyme reaction generally exhibited a lower optimal feed temperature and higher substrate conversion than in a continuously stirred tank reacto

ISSN:0268-2575    

DOI:10.1002/jctb.280500104

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractAqueous two‐phase extraction systems were developed to separate intracellular proteins from cell debris. To economize on the use of chemicals as well as to minimize environmental pollution, a closed mode of operation was sought. Various approaches to achieve recycling of salt from the primary lower phase containing 30–60% (w/w) of the added salt together with cell debris, proteins and nucleic acids were studied. Techniques assessed included microfiltration, heat treatment and the extraction with phase systems formed by aliphatic alcohols. With 20% (w/w) primary lower phase it was found to be possible to separate 95% of the salt in 3–4 theoretical steps using counter‐current ext

ISSN:0268-2575    

DOI:10.1002/jctb.280500105

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA split‐flow thin (SPLITT) cell with a perpendicular driving force of one gravity has been utilized for the rapid separation of micron‐sized particles from macromolecules. The procedure involves the simultaneous use of two transport mechanisms and thus two operating modes: a sedimentation process controls the displacement of the particles across the thickness of the thin channel, while diffusion controls the displacement of macromolecules. The theoretical equations for these two operating modes are summarized and it is shown how the two modes can be combined to yield specified recovery factors. The theory was tested on a mixture of 10 μm polystyrene latex beads and three different proteins. The observed separation was in excellent agreement with theory. Attempts to fractionate red blood cells and plasma proteins from whole blood were only partially successful as a consequence of the weak sedimentation of red blood cells. Various remedies to this problem are suggested, the most promising of which is the use of a SPLITT cell subject to mild centrifugal fo

ISSN:0268-2575    

DOI:10.1002/jctb.280500106

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractLiquid‐phase oxidation of cyclohexane with Co(III) catalyst and gaseous oxygen was found to be influenced by reaction temperature, catalyst concentration and the duration. Maximum adipic acid product selectivity (77%) with about 85% cyclohexane conversion was attained at 100°C using catalyst: cyclohexane molar ratio 0·08. Under these conditions more than 80% cyclohexane was converted in the first hour, although selectivity to adipic acid continued to increase for the next 5 h. Cyclohexyl acetate and cyclohexyl monoadipate were identified as important intermediates. This study supports the mechanism proposed by Schultz, J. G. D. and Opchenko, A., J. Org. Chem.,38(21) (1973) 3

ISSN:0268-2575    

DOI:10.1002/jctb.280500107

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSilica‐supported Ni‐Ag catalysts with a loading of 2·1·0.6% (w/w) total metal have been prepared using the precursors nickel dimethylglyoxime and silver nitrate by means of a simple impregnation method. The resulting catalysts were activated by calcination at 260°C in air, followed by hydrogen reduction at 450°C. They were then employed for soyabean oil hydrogenation at 1 bar H2 pressure and 160°C in a stirred batch reactor.Characterisation of the catalysts using temperature‐programmed reduction and electron microscopy indicated that alloying of nickel and silver had occurred, but metal particle composition, for a given overall composition, varied with metal particle size and smaller metal particles were nickel rich.The hydrogenation activity and selectivity measurements revealed that the catalysts were more active and selective than a commercial nickel catalyst. Furthermore, the specific activities of the alloy catalysts were a maximum for alloys in the range 70–90 at. % Ni. However, the supported alloy catalysts also gave rise to greater trans isomerisation than the commercial catalyst. This is attributed to hydrogen deficiency caused by large triglyceride molecules blocking hydrogen chemisorption on small nickel particles (10–50 Å in diameter), leading to enhanced cis‐tr

ISSN:0268-2575    

DOI:10.1002/jctb.280500108

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractPalladium‐copper catalysts supported upon silica, containing 2–6% (w/w) total metal, have been prepared by (i) precipitation and (ii) impregnation methods. The catalysts were employed for the hydrogenation of soyabean oil at 1 bar H2pressure and at 160°C in a stirred batch reactor.Temperature‐programmed reduction studies provided evidence of alloying of palladium and copper and metal surface area measurements exhibited evidence of a slight maximum in the metal surface area at around 90 at. % Pd content. In addition, it was observed that the presence of copper seemed to prevent sintering of palladium, giving a more stable or even enhancing metal surface area compared with palladium alone.Activity measurements showed that there was evidence of a maximum at around 80–90 at. % Pd content. However, selectivity measurements showed that the latter parameter was dominated by the presence of palladium and except at very high copper contents the superior selectivity of the latter for linolenate chain hydrogenation was hardly evident. It is thought that the palladium may cause the copper to be present largely as Cu°, which is not as effective as Cu1in catalysing selective hydrogenation of multiply unsaturate

ISSN:0268-2575    

DOI:10.1002/jctb.280500109

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractManganese hydroxide was precipitated from MnSO4and NH4OH at controlled pH, partially oxidised by aeration and finally calcined at 573–623 K to yield manganese oxide with oxidation state between +3 and +4. When the calcined oxide was leached in dilute sulphuric acid, MnO2of high electrochemical activity was obtained. In order to improve the bulk or packing density of the product various oxidants were added during the aerial oxidation of the Mn(OH)2slurry and also during the leaching in dilute H2SO4. It was observed that the best results were obtained when active MnO2was added during the aerial oxidation of Mn(OH)2slurr

ISSN:0268-2575    

DOI:10.1002/jctb.280500110

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractAlthough chromatography has been established as a powerful analytical tool, its large‐scale application is not widely appreciated. In this short review the up‐to‐date developments in the scaling‐up of chromatographic processes are considered and the designs judged to offer the greatest potential and commercial viability are described paying special emphasis to liquid applications.Sufficient references are included to enable the interested reader to pursue the subject

ISSN:0268-2575    

DOI:10.1002/jctb.280500111

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY