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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 1042-1046 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 11 (1993), S. 1007-1012 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] In situ product removal (ISPR) is the fast removal of product from a producing cell thereby preventing its subsequent interference with cellular or medium components. Over the past 10 years ISPR techniques have developed substantially and its feasibility (with improvements in yield or productivity) ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 434 (1984), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 413-418 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A continuous non-aerated process for the Δ1 of hydrocortisone by gel-entrapped Arthrobacter simplex was developed. The process employs PAAH-bead entrapped cells for the continuous conversion of up to 1.6 g/l hydrocortisone solutions in cosolvent containing buffer. Employing ethyleneglycol (10–20% (v/v)) as the cosolvent of choice and menadione sodium bisulfite as effective, non-toxic, sole electron acceptor, efficient non-aerated continuous production of prednisolone in a packed bed conlumn could be maintained, at least for the 30–40 day period of continuous operation tested. The high operational stability observed was made possible by the combined effect of immobilization technique (PAAH bead entrapment), wisely selected cosolvent and artificial electron acceptor, and elimination of aeration and vigorous mixing.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 25 (1987), S. 495-501 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of water-miscible cosolvents on biotransformations of poorly water-soluble substrates by immobilized cells was investigated, using Δ1-dehydrogenation of hydrocortisone by Arthrobacter simplex as a model. Criteria for solvent selection on the basis of retention of enzymic activity were postulated and tested. Diols were considered to be the most suitable group of solvents. Substrate solubility increased tenfold in 30% (v/v) ethylene glycol, but reaction rates were significantly slower in such solutions. This was mainly caused by a decrease of oxygen solubility in the presence of the cosolvent and conformational changes imposed on the intracellular enzyme by cosolvent molecules penetrating the cell. The inhibition could be eliminated by the addition of an artificial electron acceptor, phenazine methosulphate (PMS). Reaction rates faster than those for substrate suspensions (no cosolvent added) could thus be achieved. Immobilization of Arthrobacter simplex in cross-linked polyacrylamide hydrazide gave high retentions of activity. PMS exhibited toxic effects on the entrapped cells, leading to reduced activity after extended use.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 27 (1988), S. 457-463 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of water miscible solvents on Δ1-steroid reduction by free and polyacrylamide-hydrazide (PAAH) entrapped Mycobacterium sp. NRRL B-3805 cells was investigated. On the basis of retention of reductase activity an order of preference of diols (e.g. ethyleneglycol) 〉 DMSO 〉 DMF and monoalcohols (e.g. ethanol) as cosolvents was recorded. Significant increase in substrate (1,4-androstadiene-3,17-dione) solubility was attained in presence of the cosolvent of choice (ethyleneglycol), accompanied by some inhibition of the Δ1-reductase activity. Optimization of ethyleneglycol concentration (10–20% (v/v)) led to specific activity in a homogeneous medium, higher than recorded in the absence of cosolvent. Immobilization in PAAH gel resulted in high retention of immobilized enzymic activity, accompanied by minor diffusional limitations. Moreover, the gel exhibited protective effect of the entrapped cells from cosolvent inhibition. Modification of gel composition (e. g. hydrophobicity) had no significant effect on reaction kinetics.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A working system for studying the effects of factors involved in the chemical nature of microcarriers on cell attachment, spreading, and growth was established. The system is based on polyacrylamide beads, prepared by the emulsion polymerization technique. Sieved beads of desirable mean diameter were derivatized to generate controlled amounts of primary and tertiary amino groups. These microcarriers were used for the propagation of four different cell strains: BHK, MDCK, CEF, and MRC-5. It was found that BHK cells attach and spread significantly faster on primary amino-derivatized beads than those with tertiary amino groups, and at a lower degree of charging. Cell yields of MDCK cells (with pronounced epithelial morphology) propagated on primary amino-derivatized beads were higher than that obtained for the tertiary amino-derivatized microcarriers. On the other hand, CEF and MRC-5 cells (with pronounced fibroblast morphology) achieved higher cell yields on the tertiary amino-derivatized microcarriers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 1607-1627 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Urease was bound to commercially available nonwoven nylon fabric filters. Multilyer immoibilized-enzyme filter reactors were constructed by packing varying numbers of urease-nylon filters in a column. Owing to the relatively open structure and high mechanical strength of the filter fabric, compaction and pressure drop effects were minimal. The reactors could be operated in a wide range of substrate concentrations and flow rates under conditions where mass-transfer limitations could be neglected. The kinetic behavior of the immobilized-enzyme filter reactors could be described by a linear form of the integrated Michaelis-Menten equation using a model based on the sequential action of the enzyme filters.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 2969-2980 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a previous publication, the authors described the establishment of a working system for studing effects of factors involved in the chemical nature of a microcarrier on cell attachment, spreading, and growth. The first part of the rsearch dealt with the influence of the type and amount of the positively charged groups. In the present article, the authors will describe the effect of the introduction of hydrophobic elements onto primary amino derivatized polyacrylamide microcariers. It was found that cell attachement kinetics were gradually enhanced in parallel to a gradual increase in hydrophobicity via elongation of the hydrocarbon side-chain carrying the primary amino charged group. A threshold effect of the amount of charge required for cell attachment spreading and growth was exhibited on all the tested primary amino derivatized microcarriers. Optimum cell growth was recorded for the butylamine and hexylamine polyacrylamide microcarris. Lowre cell yields were recorded for ethylamine and octylamine derivatives. The location of the introduced hydrophobic element has a profound effect on cell propagation. Introduction of hydrophobicity onto the polymeric backbone of the microcarrier (via copolymerization of hydrophobic comonomer) lead to negative influence on cell attachement and growth yields. Out of the series of derivatized polyacrylamide microcarriers tested, it seems that the hexylamine derivative may be a potential alternative for the commonly used tertiary amine microcariers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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