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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 290-299 
    ISSN: 0006-3592
    Schlagwort(e): proteins, modified ; partitioning in aqueous system ; thaumatin ; β-lactoglobulin ; BSA ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Relatively conservative modifications of three proteins were carried out to alter their surface properties. The protein properties modified were hydrophobicity and charge. This was done by acylation of amino groups with anhydrides. For the hydrophobic modification experiments, two proteins (β-lactoglobulin and bovine serum albumin [BSA]) and four anhydrides (hexanoic, butyric, succinic, acetic) were used. For the modification of surface charge the protein thaumatin was selected and various proportions of the free amino groups were blocked with acetic anhydride to give a series of proteins with differing isoelectric points. Detailed characterization and purification of selected modified proteins was carried out including molecular weight measurements and conformational analysis. The criteria used for selecting the modified proteins for subsequent investigation of their partitioning in aqueous two-phase systems (ATPS) is described. With a judicious choice of starting material it was found that limited chemical modifications to proteins could effectively alter surface hydrophobicity or charge almost independently, with little effect on other molecular properties. It appears, however, that the method for chemical modification and the reaction conditions must also be carefully controlled. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 309-315 
    ISSN: 0006-3592
    Schlagwort(e): surface charge ; proteins, modified ; partitioning in aqueous system ; thaumatin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A series of charge-modified thaumatins with different values of surface charge were partitioned in aqueous two-phase systems (ATPS) to study the effect of surface charge as a single property on partitioning. Electrophoretic mobility of the proteins in titration curves was used as a measure of surface charge. Four modified proteins derived from thaumatin with the following values of isoelectric point: 8.70, 8.15, 5.60, and 4.50 were used for partitioning. The resolution of the systems in terms of protein surface charge was calculated. Partitioning of modified thaumatins in PEG 4000/dextran systems with phosphate buffer, Tris buffer, NaCl, KCl, and sulfate salts was carried out. Among the sulfate salts tested, the addition of 50 mM Li2SO4 to the system buffered with phosphate gave the highest value of resolution for differences in surface protein charge (RSPC). It shows a decrease in the value of K (partition coefficient) with an increase in the protein's charge. The addition of 100 mM KCl to the system promoted the opposite effect on the RSPC value. Charge-modified proteins were partitioned in PEG/salt systems to investigate the ability of these systems for resolving differences in surface charge. The PEG/citrate system seemed to have almost no ability for resolving proteins on the basis of surface charge differences; PEG/phosphate systems had some capability for resolving differently charged proteins. The more negative proteins tended to have higher values of K than the more positively charged fractions. The use of charge-modified proteins allowed the investigation of the effect of protein surface charge on partitioning in aqueous two-phase systems independently from other protein parameters as they were prepared from a common parent protein thaumatin. This technique provides an interesting novel tool to investigate the effect of protein surface charge on partitioning in ATPS taking protein charge as an independent parameter. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 628-637 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This article describes the synthesis and regulation of β(1-3)glucanase and protease enzymes from the cell lytic system of Oerskovia xanthineolytica LL-G109 in continuous culture using different concentrations of carbon source (glucose) and inducer (glucan). These two enzyme activities are the main components of a lytic system capable of lysing and disrupting whole yeast cells; it is subject to catabolite repression by glucose and is induced by yeast glucan. Peaks of β(1-3)glucanase and protease activity are obtained at dilution rates of between 0.05 and 0.15 h-1. The glucanase-protease ratio is very high compared to other strains. At dilution rates above 0.15 h-1 all activities are similar to those obtained in batch culture. The lytic enzyme system appears to contain several β(1-3)glucanase enzymes. In continuous culture both productivity and enzyme concentrations are greatly in creased when compared to batch culture, 11- and 4.4-fold, respectively.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 929-943 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A structured, mechanistic model has been built for the kinetics of yeast cell lysis by microbial cell lytic enzymes, based on an understanding of the two-layer yeast cell wall structure and the properties of yeast-lytic enzyme systems. The model predicts the release of protein, peptides and carbohydrates from four cell structures: the outer and inner wall layers, the cytosol and organelles or proteins present in particles; it also predicts organelle or particle lysis or solubilization and the breakdown of released proteins to peptides. Applications of the model to design and optimization of selective product release are discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 977-985 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A novel method has been developed for the separation of bioproducts from yeast cells. The method uses a combination of physical, chemical, and biological agents such as lytic enzymes, osmotic supports, and spheroplast stabilizers. Using this technique, products (proteins and enzymes) can be released from specific cell locations at different process states; it has thus been celled differential product release (DPR). The wall-associated proteins are released first and the lytic enzyme is removed together with the wall proteins at this stage. Secondly, the cytosol products are released by a mild procedure during which the organelles remained intact. Finally, the organelle proteins are solubilized. In each stage, specific proteins are released while others are kept inside the different cell compartments. This method can be used with relatively high yeast concentrations (up to 145 g dry wt/L) and gives higher product recoveries and much higher selectivity than mechanical disruption.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 246-256 
    ISSN: 0006-3592
    Schlagwort(e): polyethylene glycol ; phosphate ; phase separation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Phase separation times for polyethylene glycol (PEG)-4000-phosphate aqueous two-phase systems were studied, for small scale (5-g) and large scale (1300-g) systems, as a -function of the stability ratio. Profiles of dispersion height for both large and small scale systems were represented as a fraction of the initial height and were found to be independent of the geometrical dimensions of the separator. Furthermore, by plotting time as a fraction of the initial height the total time of separation can be calculated for a given height of system at a particular stability ratio. This generalization is important for the design of large scale aqueous two-phase separators. Phase separation times were also found to be dependent on which of the phases is continuous. A characteristic change in phase separation time was also observed at the phase inversion point (i.e., where the dispersed phase changes to a continuous phase and vice versa) and this point tends toward higher volume ratios as the tie-line length (TLL) is increased. Furthermore, the phase inversion point at each TLL corresponds to a fixed phosphate concentration. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 97-109 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The conditions for culture storage, inoculum preparation, and growth of a Cytophaga species, constitutive with respect to yeast-lytic enzymes, have been established in shake-flask studies and in 5 liter fermentor experiments. A low cost medium was adopted for 900 liter-scale fermentation and gave an enzyme activity in the fermentation broth somewhat greater than the comparable laboratory-scale one.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 481-490 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A simple two-step model is proposed to describe the kinetics of the two lytic systems examined in the preceding article. The model predicts concentrations of yeast solids, soluble proteins, peptides, and carbohyrates. In the first reaction step, yeast cell mass is solubilized; in the second, the released protein can be hydrolyzed to peptides. Kinetics for both yeast lysis and the subsequent protein breakdown are based on Michaelis-Menten expressions. Terms have been included for competitive inhibition of yeast lysis by substances in the Cytophaga enzyme preparation, and for incomplete hydrolysis of cells by the Oerskovia enzyme system. Parameters have been independently determined for all reactions except Oerskovia proteolysis, where they were fit by a leastsquares method to data from model test runs. The model has been verified for yeast concentrations between 0.7 and 70 g/L yeast (dry basis) and 4-40% crude enzyme solution.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1087-1094 
    ISSN: 0006-3592
    Schlagwort(e): fermentation ; optimization ; enzymatic reactions ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Two general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 29-37 
    ISSN: 0006-3592
    Schlagwort(e): proteins, contaminant ; Escherichia coli ; Saccharomyces cerevisiae ; mammalian cell culture ; PAGE ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The protein components of three industrial recombinant expression systems: Escherichia coli, Saccharomyces cerevisiae, and a mammalian cell culture supernatant of CHO cells were characterized in terms of their molecular weight, isoelectric point, and relative surface hydrophobicity. Identification of individual proteins was done by reference to their position in protein band profiles by polyacrylamide gel electrophoresis (PAGE) of the crude material. This permitted a rapid and facile assignment of quantitative values for these three parameters to all the major protein components in these materials. Because it is the indigenous proteins in expression systems that will form the bulk of any impurities in the product, once the values of these parameters are known for any target recombinant protein, the data obtained will enable appropriate expression systems to be chosen for minimizing amounts of potential contaminants and reducing downstream processing requirements and costs. The data will also indicate which fractionation steps (i.e., charge, size or hydrophobicity-based) are likely to be best for distinguishing between target and contaminant proteins, thus aiding and early removal of the maximum quantities of undesired protein to bring subsequent bioseparation steps down in scale and cost and up in terms of efficiency. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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