摘要:

AbstractMicrobial desulfurization of coal by pyrite oxidizing bacterial enrichment cultures has been studied in air‐agitated slurry reactors of 4‐ and 20‐L volumes. Batch experiments showed that inoculation with an active bacterial culture is essential to minimize the lag phase, although a considerable number of pyrite oxidizing bacteria was found on the coal prior to desulfurization. For detailed investigations of kinetics, energy requirements, and technical applicability, a bioreactor equipment consisting of a cascade of eight stages was developed and operated continuously. Microbial desulfurization of coal—monitored by measuring the axial profile of dissolved iron concentration, real and maximum oxygen consumption rates, and cell concentration—at pulp densities to 30% was performed over a period of 200 days without any disturbances concerning the aeration system, fluidization, transport of solids and microbial growth. At a pulp density of 20%, a pyrite conversion of 68% was achieved after the third reactor stage at a total residence time of five days in the first three stages. The kinetics of pyrite degradation were found to be well described by a rate equation of first order in pyrite surface area concentration if the pyrite is directly accessible for microbial attack. Rate constants were determined to 0.48 mg pyrite/(cm2day) in the first and to 0.24 mg pyrite/(cm2day) in the following reactor stages. Kinetic models taking into account adsorption/desorption as well as growth kinetics failed to describe the observed reaction rates. However, a model treating pyrite degradation and microbial growth kinetics formalistically seems to be applicable when backmixing between the reactor stages can be avoided. The advantage of a multistage reactor in comparison to single‐stage equipment was shown by calculation. To obtain a pyrite conversion of 68%, a three‐stage reactor would require only 58% of the volume of single‐stage equipment.Measurement of oxygen consumption rates proved to provide quickly and easily measurable parameters to observe microbial coal desulfurization in technical scale: the real oxygen consumption rate is correlated to the pyrite oxidation rate and the maximum oxygen consumption rate is correlated to the concentration of viable cells. The Yo/scoefficient for the amount of oxygen consumed per mass unit of pyrite oxygen was determined to approximately 0.33 in comparison to 1.0 which can be calculated from stoichiornetry. This could yet not be explained. Chemical leaching experiments as well as sulfur analyses of desulfurized coal samples showed that the microorganisms play the main role in degradation of pyrite from coal and that pyrite oxidation by ferric iron c

ISSN:0006-3592    

DOI:10.1002/bit.260341102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractMonocrotaline, a pyrrolizidine alkaloid of chemotherapeutic interest, was successfully extracted from the crushed seeds ofCrotalaria spectabilisusing supercritical carbon dioxide and ethanol mixtures. Overall solubilities of the plant material in the supercritical fluid phase were as high as 1.1 mass percent, and monocrotaline solubilities were as high as 0.07 mass percent. The solubility of monocrotaline in the presence of other plant material was smaller by 50 to 98% compared with the solubility of pure monocrotaline in the supercritical fluid. Also, it was found that the extraction of the complex plant material was time‐dependent after approximately one percent of the original mass of the material had been extracte

ISSN:0006-3592    

DOI:10.1002/bit.260341103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe immobilization of heparinase to tresyl‐chloride‐activated cellulose hollow fibers for the removal of heparin from the bloodstream was examined. Whole blood can be circulated through cellulose hollow fibers without hemolysis and the tresyl chloride chemistry provides a strong linkage which limits the release of the enzyme from the support. The tresylation and immobilization methods were modified and optimized to improve the heparinase activity retained by cellulose. Pretreatment of the hollow fibers with 0.05/V sodium hydroxide increased the degree of tresylation and the immobilization yield by a factor of five. The use of triethylamine as the organic base in the tresyl chloride activation resulted in threefold greater activity retention by the support than when pyridine was used. Together, sodium hydroxide pretreatment and triethylamine enhanced the activity retained by cellulose to 26.2 ± 7.0% of that bound to the support. The activity retention was also a function of the technique used for immobilization. The best results were achieved when the enzyme was applied to the activated fibers once every 12 to 24 h for a total of four times. The active enzyme loading on the fibers was 0.3 mg heparin degraded/h cm2when 4.5 μg protein/cm2was bound to the f

ISSN:0006-3592    

DOI:10.1002/bit.260341104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractImmobilized enzyme hollow fibers may be useful in the purification or treatment of whole blood under clinical conditions. In this study, catalytically pure heparinase was immobilized to cellulose to analyze the feasibility for the removal of heparin's anticoagulant activity from whole blood. The kinetics of catalytically pure heparinase immobilized to regenerated cellulose hollow fibers were quantified with respect to mass transfer coefficient and enzyme loading. The kinetic analysis showed that increases in the mass transfer coefficient of heparin in the fiber lumen decreased the apparent Michaelis constant while increases in enzyme activity immobilized to the fiber lumen increased the apparent Michaelis constant. The apparent Michaelis constant was an order of magnitude greater than the intrinsicKmvalue for the system. The intrinsicKmvalue for heparinase–cellulose is 0.4 ± 0.3 mg/mL (N= 6) and it is the same order of magnitude as theKmvalue for soluble heparina

ISSN:0006-3592    

DOI:10.1002/bit.260341105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe initial testing of the safety of a cellulose–heparinase hollow fiber device was assessed with respect to physical properties andin vitrobiocompatibility. The material cleared urea and creatinine without passing albumin, even at high flow rates. The clearance of urea and creatinine by cellulose–heparinase was equal or slightly reduced in comparision to the cellulose device. The cellulose–neparinase device tolerance to now rates was also unchanged. In addition, scanning electron microscopy of the lumen established the uniformity of the material. The analysis of clearance rates and the scanning electron micrographs show there to be no damage to the cellulose membrane after tresyl chloride activation and heparinase immobilization. The investigation of biocompatibility in anin vitrotest system with whole human blood indicated that there were no significant changes in the biocompatibility of cellulose with bound heparinase. There was no change in the level of red blood cells, white blood cells, or platelets over the course ofin vitrowhole blood perfusion through cellulose or cellulose–heparinase hollow fiber devices. Low levels of plasma hemoglobin and complement activation were observed with cellulose and cellulose–heparinase devices. Thus, the cellulose hollow fibers can be functionalized without any changes inin vitrope

ISSN:0006-3592    

DOI:10.1002/bit.260341106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260341107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260341108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260341109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260341110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260341101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY