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  • 1
    Electronic Resource
    Electronic Resource
    The importance of bead size measurement in mass-transfer modelling with immobilised cells (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 440-444 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effective diffusivity of O2 inside immobilised cell particles has been much discussed. Most reported estimates are based on fitting a mass-transfer reaction model to measured total oxygen uptake rates. The particle diameter has the largest single influence in such models, but its accurate measurement has probably recieved insufficient attention. We have studied sorbitol and glucose oxidation by cells of Gluconobacter suboxydans entrapped in calcium alginate gel beads. These beads were found to shrink rapidly in air, so that size measurement under water is essential. By comparison with rigid particles of similar known size, it was shown that measurement of the microscopic image gives a systematic underestimate. In consequence, the fitted oxygen diffusivity will be around 20% too low. Careful attention to size measurement gave good agreement between diffusivity estimates from beads with different mean sizes and cell loadings, with a best value of 2.51 × 109 m2s−1, 92% of the value for pure water. The estimated diffusivity is not significantly affected by a distribution of bead sizes with up to 10% standard deviation about the same mean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218446
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrolysis of lactose in milk by lactase immobilized to a non-porous magnetic support (1979)
    Springer
    Applied microbiology and biotechnology 8 (1979), S. 27-36 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary 1. Lactases immobilized to sub-micron ferrite particles hydrolyse lactose in whole milk, from which they are easily recovered magnetically. 2. Neither type of lactase available on a large scale has ideal properties for use in an immobilized derivative. Fungal lactase has low activity at the pH of milk, while the yeast enzyme is inactivated by a component of milk. 3. The non-porous magnetic catalyst is only weakly fouled in whole milk, and foul is readily removed by agitation in buffer or detergent solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00510263
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Recovery of free enzymes from product liquors by bio-affinity adsorption: Trypsin binding by immobilised soybean inhibitor (1979)
    Springer
    Applied microbiology and biotechnology 6 (1979), S. 195-205 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Soybean trypsin inhibitor immobilised to sub-micron ferrite particles functions as an affinity adsorbent for trypsin and the adsorbed enzyme may be recovered following elution in dilute acid. Trypsin can be adsorbed from casein solutions that is has digested. Equilibrium is reached in under 2 min with an effective dissociation constant as low as 10−7 M, allowing recoveries of more than 90% of added enzyme under realistic conditions. These results suggest that bioaffinity adsorbents could be used to recover an enzyme that has converted a macromolecular substrate. The operation of such a process is discussed, and some interactions are described that could be used with suitably high affinity adsorbents for other enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508091
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The importance of bead size measurement in mass-transfer modelling with immobilised cells (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 440-444 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The effective diffusivity of O2 inside immobilised cell particles has been much discussed. Most reported estimates are based on fitting a mass-transfer reaction model to measured total oxygen uptake rates. The particle diameter has the largest single influence in such models, but its accurate measurement has probably received insufficient attention. We have studied sorbitol and glucose oxidation by cells of Gluconobacter suboxydans entrapped in calcium alginate gel beads. These beads were found to shrink rapidly in air, so that size measurement under water is essential. By comparison with rigid particles of similar known size, it was shown that measurement of the microscopic image gives a systematic underestimate. In consequence, the fitted oxygen diffusivity will be around 20% too low. Careful attention to size measurement gave good agreement between diffusivity estimates from beads with different mean sizes and cell loadings, with a best value of 2.51×109 m2s-1, 92% of the value for pure water. The estimated diffusivity is not significantly affected by a distribution of bead sizes with up to 10% standard deviation about the same mean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050431
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Novel reactor for aqueous-organic two-phase biocatalysis: A packed bed hollow fiber membrane bioreactor (1993)
    Springer
    Biotechnology techniques 7 (1993), S. 441-446 
    Details
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Hollow fiber membranes were potted in a tubular shell with a particulate, microporous, enzyme bearing support packed in the shell space. A bicontinuous system was thus formed with the reactants, supplied through the shell and the fiber lumen, forming an interface at the surface of the particles. Acid production rates, without any reactor optimization, up to four times greater than with membrane reactors were obtained during the lipase catalyzed hydrolysis of ethyl laurate and olive oil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151881
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  • 6
    Electronic Resource
    Electronic Resource
    Improved nonporous magnetic supports for immobilized enzymes (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 393-416 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ni powders coated by deposition of TiO2 or controlled oxidation to NiO develop substantial resistance to corrosion. Chymotrypsin immobilized to these coated Ni supports shows very high stability of activity on storage. Chymotrypsin immobilized by adsorption and glutaraldehyde crosslinking was fairly rapidly eluted under operational conditions in the presence of substrate. If 3-aminopropyltriethoxysilane (APS) was used to produce a covalent linkage, desorption of enzyme still occurred because of relatively unstable bonding of the silane to the oxide surface. A more stable attachment was produced by joining together many silane links with a layer of polyglutaraldehyde. The mechanism of action of APS as a coupling agent under these conditions is discussed. γ-Fe2O3, and particularly a Mn-Zn ferrite, are suitable magnetic support materials available with smaller particle sizes. Particles below 1 μm give the expected higher specific activities of immobilized enzymes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260210304
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  • 7
    Electronic Resource
    Electronic Resource
    Reusable enzyme catalysts for particulate and macromolecular reactants and fouling media (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 2365-2367 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260211218
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Nonporous magnetic supports for proteases, cell-lytic enzymes, and ribonuclease: Limits of reactant size (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 2359-2363 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260211217
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Surfactant-induced breakthrough effects during the operation of two-phase biocatalytic membrane reactors (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 765-771 
    Details
    ISSN: 0006-3592
    Keywords: membrane bioreactors ; two-phase ; surfactant adsorption ; membrane wettability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Surface-active components, both reactants and products, are frequently encountered in two-phase, aqueous-organic, biocatalytic reactions, When such reaction are carried out in a membrane reactor, employing a membrane selectively wetted by one of the two reactants, changes in the content of these surfactants- as a consequence of the progress of the reaction-can lead to wetting transitions at the two membrane-liquid interfaces as a result of adsorption of the tenside. This can lead to a decrease in the pressure required to cause the, initially, nonwetting phase to break through the membrane. Such effects render difficult the operation of two-phase membrane bioreactors. Hence, it is necessary to make a careful selection of the membrane material and type by considering factors such as UF versus MF and low MWCO versus high MWCO to enable the reactor to be operated without breakthrough, but without significantly compromising the reaction rates that can be maintained.The phenomena leading to breakthrough effects are discussed in this paper, and experimental results for the hydrolysis of ethyl laurate by lipase from Candida rugosa in a batch flat sheet membrane reactor are presented with the reactor operated with a variety of membranes. An experimental result showing the decrease in the pressure required to cause breakthrough of the organic phase (for the system ethyl laurate-lauric acid-water) as the content of the highly surface-active lauric acid in the organic phase is increased is also presented for an asymmetric, hydrophilic meta-aramid ultrafiltration membrane. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440613
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Continuous in situ water activity control for organic phase biocatalysis in a packed bed hollow fiber reactor (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 284-289 
    Details
    ISSN: 0006-3592
    Keywords: organic phase biocatalysis ; esterification ; water activity ; lipase ; biocatalysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Packed bed hollow fiber membrane reactors were used to carry out organic phase biocatalysis at constant water activity. The performance of the device was tested by carrying out the esterification of dodecanol and decanoic acid in hexane. Lipase from Candida rugosa, immobilized on microporous polypropylene and packed in the shell space of the reactor, was used to catalyze the reaction. In situ water activity control was accomplished by pumping appropriate saturated salt solutions through the microporous hollow fiber polypropylene membranes. Water generated by reaction in the organic phase, pumped continuously through the shell of the reactor, was transferred into the bulk of the aqueous phase under the water activity gradient. The reactor performance was found to be strongly dependent on the controlling water activity. By carefully selecting this control activity it was found possible to obtain complete esterification. The water activity of the organic phase could be maintained very close to that of the saturated salt solution used. The reactor could be operated in the continuous mode for 100 h without any degradation in its performance. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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