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  • 1
    Electronic Resource
    Electronic Resource
    The influence of electrostatic interactions on partition in aqueous polyethylene glycol/dextran biphasic systems: Part II (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 252-260 
    Details
    ISSN: 0006-3592
    Keywords: aqueous two-phase systems ; polyethylene glycol-dextran systems ; electrostatic potential ; hydrophobicity ; surface tension ; polyelectrolytes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In aqueous polyethylene glycol/dextran two-phase systems, the hydrophobicity, free volume, surface tension, and interfacial tension of the phases in equilibrium were measured as a function of pH and ionic strength. These parameters were found to change with pH, but the pattern and magnitude cannot explain the unusual partition of charged macromolecules, observed previously. The electrostatic potential difference was determined by a new experimental approach based on the measurement of the pH difference between the phases at equilibrium. In polyethylene glycol/dextran systems containing sodium chloride as ionized species, the electrostatic potential is not constant in the pH range 2 to 11. The partition behavior of charged macromolecules and its dependence on pH can be explained by the combined action of charge and phase potential. This conclusion was tested with poly-L-glutamate, which partitioned as predicted and in a pattern opposite to positively charged macro- molecules. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470217
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  • 2
    Electronic Resource
    Electronic Resource
    Large scale enzymatic synthesis of nucleoside-5′-monophosphates using a phosphotransferase from carrots (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 1449-1458 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic synthesis of nucleoside-5′-monophosphates from purineriboside, 6-mercapto-purine riboside, 6-methylmercapto-purine riboside, 6-chloro-purine riboside, tubercidin, 8-aza-adenosine, and 3′-deoxy-adenosine is described in gram scale. The synthesis is catalyzed by a phosphotransferase from carrots and uses phenylphosphate as phosphate donor. The reaction products are purified on QAE-Sephadex A25 columns. The large scale preparation of the enzyme is also reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260161103
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  • 3
    Electronic Resource
    Electronic Resource
    Protein partitioning at the isoelectric point: Influence of polymer molecular weight and concentration and protein size (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 986-994 
    Details
    ISSN: 0006-3592
    Keywords: protein partitioning ; polyethyleneglycol/dextran systems ; isoelectric point ; polymer molecular weight ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report the partition coefficient, Kp′ at the isoelectric point of lysozyme, chymotrypsinogen A, albumin, transferrin, and catalase in 64 different polyethylene(PEG)/ dextran(Dx)/water systems. We study the trends of the partition coefficient with protein type, polymer concentration, and polymer molecular weight. We find that the partition coefficient decreases with increasing tie line length for lysozyme, albumin, transferrin, and catalase for which Kp is less than 1, but increases for chymotrysinogen for which Kp is larger than 1. The effect of the tie line length on the partition coefficient is larger for the large proteins than for the small proteins. The partition coefficient decreases with increasing protein molecular weight except for lysozyme suggesting that lysozyme is present as a dimer or a trimer. The partition coefficient decreases with increasing PEG molecular weight, but the magnitude of the increase is larger for the smaller PEG molecular eights and tends to level of at high PEG molecular weight. The partition coefficient increases with increasing dextran (Dx) molecular weight for chymotrypsinogen but decreases for catalase. The partition coefficients of lysozyme, albumin, and transferrin increase with increasing Dx molecular weight from Dx 104 to Dx 1.1 × 105 and then slightly decrease from Dx 1.1 × 105 to Dx 5 × 105. The experimental results are analyzed using a statistical thermodynamics model. The experimental results are analyzed using a statistical thermodynamics model. The experiments suggest that protein partitioning at the isoelectric point in aqueous two-phase systems is strongly related to the size of the proteins and polymers. Finally, the impossibility of obtaining data completely independent of polymer concentration is emphasized.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380905
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  • 4
    Electronic Resource
    Electronic Resource
    A two-step enzymatic synthesis of dipeptides (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 132-140 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic synthesis ; continuous production ; anion-exchange ; peptide-amidase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple system is introduced to produce dipeptides continuously by enzyme catalyzed condensation of amino acid esters and amino acid amides. Synthesis of N-terminal free dipeptide-amides is achieved by means of carboxypeptidase Y. The peptide-amide is deamidated utilizing a newly isolated peptide-amide is deamidated utilizing a newly isolated peptide-amidase. Separation of substrates and products is accomplished by anion-exchange chromatography. Modeling of the reactions shows that the two reactions have to be carried out in a cascade of two reactors in order to prevent hydrolysis of the peptide by the carboxypeptidase. Continuous production of Kyotorphin (H-TyrArg-OH) with a space-time yield of 257 g/L · d shows the feasibility of this concept.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390203
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  • 5
    Electronic Resource
    Electronic Resource
    Technical aspects of separation using aqueous two-phase systems in enzyme isolation processes (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 1967-1988 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Technical aspects of the separation of aqueous two-phase systems in a commercial separator were studied in detail. For the Gyrotester B, the smallest available separator, a flow rate of 200 ml/min and a length of the regulating screw in the outlet port of 13.5 mm were found as optimal operation parameters for the separation of a poly(ethylene glycol) (PEG)/dextran two-phase system. In the presence of cells and cell debris the characteristics of the carrier two-phase systems are changed, most notably the phase ratio. Nevertheless good separation and high throughput can be maintained up to 30% wet cell material in the complete system. Using this method the enzyme pullulanase was extracted from 6.65 kg Klebsiella pneumoniae in 88% yield in a single step in less than 2 hr. A yield of 90% was predicted for this step based upon laboratory data, indicating that the performance of the extraction and separation can be calculated with the necessary accuracy and the further scale-up of the process should be accomplished quite easily. The hydrophilic polymers Constituting the phase system will often stabilize the enzymes, So that the separation can be carried out at room temperature without extensive cooling. The method of enzyme solubilization or cell disruption is not decisive for the successful extraction of the enzymes, the only limitation being the necessity to find a suitable two-phase system where the desired product and the cells or cell debris will partition in opposite phases. This is shown for α-glucosidase from Saccharomyces carlsbergensis and three aminoacyl-tRNA-synthetases from Escherichia coli. The results obtained demonstrate that aqueous two-phase systems can be separated in commercially available separators with high capacity and efficiency. It can be expected that the advanced separation technology available from chemical engineering studies can also be used for the development of large-scale isolation processes for enzymes involving liquid-liquid partitions.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260201211
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  • 6
    Electronic Resource
    Electronic Resource
    Evaluation of crude dextran as phase-forming polymer for the extraction of enzymes in aqueous two-phase systems in large scale (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 24 (1982), S. 1015-1045 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed study of the influence of crude dextran on enzyme extractions in aqueous phase systems is presented in this article. The physical parameters of crude dextran, a purified T-500 fraction from Pharmacia, and a hydrolyzed crude dextran are compared and their influence on the phase system parameters investigated. Initially there is a drastic increase in the viscosity of the lower dextran-rich phase and a significant shift in the macroscopic structure of these phases, observed as the “gel-forming” properties of the dextran phases. The latter can be important for the partition of any enzyme by influencing the effect of phosphate concentration on the partition of proteins, although these experiments show that the partition coefficient of several enzymes is not much altered. The partition parameters allow the substitution of Dextran T-500 fractions by crude dextran or unfractionated, slightly hydrolyzed fractions. Using crude dextrans the performance and technical realization of enzyme extraction processes are demonstrated for pullulanase from Klebsiella pneumoniae and formate dehydrogenase from Candida boidinii.Both enzymes were recovered in comparable high yields. The equipment performance was quite good, as indicated by the high throughput values of the separators employed. Especially when using nozzle separators for phase separation there is a better performance in comparison to the Dextran T-500 fraction. No serious technical problems were encountered when replacing the expensive fractionated dextran with a crude dextran. In this way aqueous two-phase systems containing dextran become more feasible for enzyme purification from an economic point of view. The price of about 1.30 German marks (DM) per liter for a useful phase system already appears acceptable for the production of valuable intracellular enzymes.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260240502
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  • 7
    Electronic Resource
    Electronic Resource
    Procedure for the simultaneous large-scale isolation of pullulanase and 1,4-α-glucan phosphorylase from Klebsiella pneumoniae involving liquid-liquid separations (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 1989-2005 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure for the simultaneous large-scale isolation of pullulanase and 1,4-alpha;-glucan phosphorylase from Klebsiella pneumoniae is described. The pullulanase is solubilized from the cell wall by cholate treatment; cells and cell debris are removed by partition in a poly(ethylene glycol) (PEG)-dextran two-phase system and from the upper (PEG) phase of this system the pullulanase is isolated by ultrafiltration and precipitation with N-cetyl,N-,N-,N-trimethyl ammonium bromide to a purity of about 80% with a yield of 70%. The preparations are free of α-amylase activity. The cell containing dextran-rich phase is passed through a Manton-Gaulin homogenizer. Then the phosphorylase is separated from the cell debris by partition in a second PEG-dextran system. From the top phase of this system the phosphorylase is isolated by distribution in a PEG-salt two-phase system followed by batch adsorption on carboxymethyl-Sephadex in a yield of 55%, a purity of around 90%, and nearly free of glycosyltransferase activity. All steps in the isolation of the two enzymes can be performed easily in a large scale.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260201212
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  • 8
    Electronic Resource
    Electronic Resource
    Affinity partitioning: Development of mathematical model describing behavior of biomolecules in aqueous two-phase systems (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 514-520 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model describing the affinity partitioning of macromolecules in aqueous two-phase systems has been derived. The model was used to calculate binding parameters that were compared against values deter mined by means of ultracentrifugation and fluorescence titration. The mathematical model and its modifications were found to describe satisfactorily the partition behavior of macromolecules with differing numbers of binding sites. It could be shown that in solutions containing PEG the binding behavior of FDH is changed fundamentally. The dissociation constants of FDH with PEG-blue in the presence and absence of PEG are different.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300408
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  • 9
    Electronic Resource
    Electronic Resource
    Continuous production of L-phenylalanine by transamination (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 482-487 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: L-Phenylalanine was produced continuously from L-as-partate and phenylpyruvate by transaminase from a newly screened Pseudomonas putida strain. The process was carried out with an isolated enzyme in homogeneous phase in an enzyme membrane reactor and with immobilized whole cells in a stirred tank reactor, respectively. Due to the difference in transport resistance, the productivity of the free enzyme in homogeneous phase (72 mmol/L h) was about 3 times higher than the productivity achieved using immobilized cells. However, a better stability of the biocatalyst was observed with immobilized cells.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290412
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  • 10
    Electronic Resource
    Electronic Resource
    Dye-ligand membranes as selective adsorbents for rapid purification of enzymes: A case study (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 33-40 
    Details
    ISSN: 0006-3592
    Keywords: downstream ; purification ; dye-ligand ; affinity membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new adsorbent for the selective binding of enzymes, in the form of microporous membranes carrying triazine dyes as pseudo-affinity ligand, has been implemented in the recovery of glucose-6-phosphate dehydrogenase from yeast. A detailed investigation of the process parameters has been performed. In the adsorption step, the contact time for binding G6PDH could be reduced down to 0.25 s without significant decrease of the capture efficiency. Hence, fast filtration allowed to isolate G6PDH from a dilute extract (1.6 μg G6PDH · mL-1), where the enzyme accounted for 1% of the proteins. The yield of the selective elution step using NADP was only 70% at best. It could be improved to near 100% by supplementing the eluent with ethylene glycol, without loss of selectivity. A Scale-up of the cross-section of the membrane by a factor of 40 allowed to purify 1140 U from 0.6 L extract from 1% to 57% purity with 82% yield, within 10 minutes. The case study presented here demonstrates the applicability of general-purpose membrane adsorbents for the purification of enzymes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400106
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