Bioreactors catalytic

Finding (Pueblo) PH-7. Dioxins and furans are produced in the continuous steam treater (CST) under certain conditions. Some of these dioxins and furans are eventually fed to the immobilized cell bioreactors via the purge stream of the CST quench tower and are then stripped from the bioreactors and partially destroyed in the catalytic oxidation units. Activated carbon adsorbers might, therefore, be necessary downstream of the bioreactor catalytic oxidation units. 

Recommendation (Pueblo) PH-7. Results of the completed tests of engineering design studies should be carefully reviewed to ensure that activated carbon adsorbers do not have to be added to the bioreactor catalytic oxidation units to achieve acceptable levels of dioxins and furans. 

Biocompatible nanosized polyamidoamine (PAMAM) dendrimer films provided a suitable microenvironment for heme proteins to transfer electron directly with underlying pyrolytic graphite electrodes. The Mb-PAMAM film can catalytically reduced oxygen, hydrogen peroxide, and nitrite, indicating that the potential applicability of the film can be used to fabricate a new type of biosensor or bioreactor based on the direct electron transfer of Mb [234],... 

Fluidized-bed applications, 11 793—794 Fluidized-bed bioreactor, defined, 3 758t Fluidized-bed catalytic cracking (FCC), 11 793 12 402-403. See also Fluid catalytic cracking (FCC) Fluidized-bed cracking... 

The possibility of having membrane systems also as tools for a better design of chemical transformation is today becoming attractive and realistic. Catalytic membranes and membrane reactors are the subject of significant research efforts at both academic and industrial levels. For biological applications, synthetic membranes provide an ideal support to catalyst immobilization due to their biomimic capacity enzymes are retained in the reaction side, do not pollute the products and can be continuously reused. The catalytic action of enzymes is extremely efficient, selective and highly stereospecific if compared with chemical catalysts moreover, immobilization procedures have been proven to enhance the enzyme stability. In addition, membrane bioreactors are particularly attractive in terms of eco-compatibility, because they do not require additives, are able to operate at moderate temperature and pressure, and reduce the formation of by-products. 

Additional information on mechanically agitated gas-liquid-solid reactors can be obtained in van t Riet and Tramper (Basic Bioreactor Design, Marcel Dekker, 1991), Ramachandran and Chaudhari (Three-Phase Catalytic Reactors, Gordon and Breach, 1983), and Gianetto and Silveston (Multiphase Chemical Reactors, Hemisphere, 1986). Examples... 

The last systematic description of heme peroxidases was published in 1999 by Brian Dunford, from the University of Alberta in Canada. The book Heme peroxidases covers discussion on three-dimensional structure, reaction mechanism, kinetics, and spectral properties of representative enzymes from bacterial, plant, fungal, and animal origin. Since 1999, vast information on basic but also applied aspects of heme peroxidases has been generated. We believe fusion of these two aspects will benefit research of those dedicated to development of biocatalytic process. The aim of this book is to present recent advances on basic aspects such as evolution, structure-function relation, and catalytic mechanism, as well as applied aspects, such as bioreactor and protein engineering, in order to provide the tools for rational design of enhanced biocatalysts and biocatalytic processes. The book does not include an exhaustive listing of references but rather a selected collection to enrich discussion and to allow envisioning future directions for research. 

In our view, genetic engineering of future enzymes for industrial uses should consider not only their catalytic properties, but also their potential for isolation and immobilization. Designing enzymes to allow selective, high affinity immobilization by adsorption on a relatively inexpensive matrix should greatly increase the attractiveness of enzyme bioreactor processes. 

Gemeiner et al. (1993) presented a similar method for the direct determination of catalytic properties of immobilized cells. Cephalosporin C transforming Trigonopsis variabilis were immobilized by three different methods, filled into a column and set into the ET. After thermal equilibration, Cephalosporin C solutions (0.1-50 mmol/1) were continously pumped through the ET until steady-state heat production was obtained. Again, the ET was shown to be suitable for a rapid and simple estimation of the kinetic properties of immobilized cells. Microkinetic factors such as mass transfer were taken into account (Stefuca et al. 1994). Thus, ET measurements allow us to obtain intrinsic data, even from immobilized cells. Moreover, the data can be applied to optimize biocatalyst design and bioreactor models (Gemeiner et al. 1996). 

The most suitable driving force in BI is the reduction of the diffusion path that already operates in transport processes across biological bilayers. Consequently, biocatalyst membranes and specially designed bioreactors, such as jet loop and membrane reactors, are available to intensify biochemical reactions. " " Supported biocatalysts are often employed to enhance catalytic activity and stability and to protect enzymes/ microorganisms from mechanical degradation and deactivation.f Immobilization of the cells is one of the techniques employed to improve the productivity of bioreactors. 

Marconi, J.G.S. Tsotsis, T.T. Membrane bioreactors. In Catalytic Membranes and Membrane Reactors, Wiley-VCH Weinheim, 2002 Chapter 4, 15-96. 

Enzymes are proteins that have been optimized by evolution for more or less specific metabolic reactions in living cells. Reaction conditions therein are often far away from those in industrial bioreactors. By immobilization novel characteristics can be induced to make enzymes tolerant to even harsh reaction environments. Some attempts to intentionally modify the catalytic behavior have been reviewed [15]. The immobilization procedure should be conducted in a way that allows the enzyme to maintain its active conformation and necessary catalytic flexibility. Furthermore, catalytically essential residues of the enzyme should be undisturbed and conserved. 

The most commonly utilized catalytic membrane reactor is the PBMR, in which the membrane provides only the separation function. The reaction function is provided (in catalytic applications) by a packed-bed of catalyst particles placed in the interior or exterior membrane volumes. In the CMR configuration the membrane provides simultaneously the separation and reaction functions. To accomplish this, one could use either an intrinsically catalytic membrane (e.g., zeolite or metallic membrane) or a membrane that has been made catalytic through activation, by introducing catalytic sites by either impregnation or ion exchange. This process concept is finding wider acceptance in the membrane bioreactor area, rather than with the high temperature catalytic reactors. In the latter case, the potential for the catalytic membrane to deactivate and, as a result, to require sub-... 

The way membranes (in various forms, i.e., cylindrical, coaxial, flat-sheet, spiral-wound, and hollow fiber, etc.) couple with the bioreactor depends on the role the membrane performs. As with catalytic and pervaporation membrane reactors, the simplest configuration consists of two separate but coupled units, one being the bioreactor the other the membrane module. The biocatalyst (e.g., enzymes, bacteria, yeasts, mammalian cells) could, in this case, be suspended in a solution and continuously circulated through the... 

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