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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 557-562 
    ISSN: 0006-3592
    Keywords: membrane-fixed enzymes ; invertase ; amyloglucosidase ; enzyme distribution ; enzyme reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Invertase as well as as amyloglucosidase were immobilized within asymmetyric ultrafiltration membranes that were prepared from polysulfone or homogeneously modified polysulfone. The chemical modification was carried out by sulfonation and halomethylation. This additional change of the surface properties of the capillaries within the membrane offers the possibilities for various types of enzyme fixation, namely adsorption, charge interactions, or covalent bonding. By variation of the immobilization conditions the distribution of the enzyme could be adjusted over the membrane's cross section. At a distinct enzyme concentration in the loading solution a homogeneous enzyme distribution within the membrane could be verified. This was shown by diffusion experiments. Under ultrafiltration conditions using a solution that contains membrane-impermeable macromolecules as well as a membrane-permeable solute like saccharose the residence time within the membrane was increased due to gel formation atop the membrane yet the kinetic was no affected. The nonpermeable soluble starch was not reacted by the amyloglucosidase membrane, indicating that the skin layer was free of enzymes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 725-731 
    ISSN: 0006-3592
    Keywords: urease ; ultrafiltration membranes ; covalent bonding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asymmetric ultrafiltration membranes suitable for covalent bonding of urease can be prepared from membranes based upon polyamide or polysulfone. Because the original membrane polymers are not chemically reactive, they have to be converted in such a way that known reactions for enzyme fixation can be used such as the diazo, the acyl-acid, the carbodiimide, and the methylbromide reaction. The enzyme was fixed within the porous substructure of the membrane. The amount of enzyme immobilized at the membrane dense skin was found to be negligible. The kinetics can be described according to the Michaelis-Menten model. Compared to the native urease, the activity of the membrane-bonded enzyme was very low. The reasons can be sought in the transmembrane transport and in the fixation procedure as well.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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