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  • 1
    Digitale Medien
    Digitale Medien
    Complexes of block copolymers in solution: Tree approximation (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 1069-1098 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Block copolymers ; generating function ; Polya's theorem ; gelation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We determine the statistical properties of block copolymer complexes in solution. These complexes are assumed to have the topological structure of (i) a tree or of (ii) a line-dressed tree. In case the structure is that of a tree, the system is shown to undergo a gelation transition at sufficiently high polymer concentration. However, if the structure is that of a line-dressed tree, this transition is absent. Hence, we show the assumption about the topological structure to be relevant for the statistical properties of the system. We determine the average size of the complexes and calculate the viscosity of the system under the assumption that the complexes geometrically can be treated as porous spheres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01020049
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  • 2
    Digitale Medien
    Digitale Medien
    Complexes of block copolymers in solution: A graph-theoretical approach (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 1099-1122 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Block copolymers ; generating function method ; Polya's theorem ; gelation ; nonnested structures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We determine the statistical properties of block copolymers in solution. These complexes are assumed to have the topological structure of connected graphs with “nonnested” loops and cycles. The generating function method is used to determine the number of topologically different complexes containing a given number of block copolymers. It is shown that at sufficiently high concentration the system undergoes a transition to a gel phase. Furthermore, the average number of polymers per complex is calculated. Finally, the relative increase in viscosity is found under the assumption that the complexes can be treated as porous spheres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01020050
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  • 3
    Digitale Medien
    Digitale Medien
    Dialysis fermentation. III. Anomalous inhibition of threonine biosynthesis in an auxotrophic mutant of Escherichia coliArticle No. 4979, Michigan Agricultural Experiment Station. (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 12 (1970), S. 603-613 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Dialysis was attempted as a means to alleviate the product-activated controls presumed to limit the formation of threonine by an auxotrophic mutant of Escherichia coli strain W. The occurrence of inhibition rather than enhancement of yields by dialysis was traced to the fact that threonine actually was not inhibiting its own synthesis. Instead, α,ε-diaminopimelic acid became depleted, but the imbalance could not be corrected by exogenous replacement.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260120409
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  • 4
    Digitale Medien
    Digitale Medien
    Dialysis fermentation. I. Enhanced production of salicylic acid from naphthalene Pseudomonas fluorescensArticle No. 4977, Michigan Agricultural Experiment Station. (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 12 (1970), S. 577-589 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The conversion of naphthalene to salicylic acid by Pseudomonas fluorescens was studied as a model for dialysis fermentation. In a demonstration experiment, the continual removal of the product by dialysis and by intermittent replenishment of the dialysate reservoir caused cyclical changes in the concentrations of viable cells and product. The cumulative total amount of both cell mass and salicylate, however, continued to increase steadily until the experiment was terminated after 15 days. At this time the rate of product formation was highest and still increasing, although less than 10% of the cells were viable. The terminal amount of salicylate was about 20-fold greater than the maximum reached in the control fermentation, and was calculated to be 2.6-fold more productive even if the control were optimally recycled. Methods were projected to achieve still further improvements.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260120407
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of alkylbenzenes on n-alkane utilization (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 441-448 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: It has been shown that alkylbenzenes which do not support growth of Pseudomonas aeruginosa exert a stimulatory or inhibitory effect on the utilization of n-alkanes by this organism. The effect is a function or the number of methyl substitutions to the benzene ring and the concentration of aromatic hydrocarbon. The alkylbenzenes have been shown to exert the stimulatory and inhibitory effect, on all phases of growth. The data suggests different mechanisms involved in the inhibition by benzene and p-xylene but a similar mechanism by all of the stimulatory compounds. Warburg data demonstrates changes in the rate of oxygen uptake in the presence of trimethylbenzene at different stages of the fermentation. The release of water soluble material in the presence of trimethylbenzene suggests a permeability effect on the cells.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260110315
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  • 6
    Digitale Medien
    Digitale Medien
    The relationship of substrate, growth rate, and maintenance coefficient to single cell protein production (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 117-127 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Various organic compounds were assessed as potential substrates for single cell protein production. Substrate evaluation was based on the costs associated with the substrate, oxygen, and heat yield coefficients: Ysub, Yo, and Ykcal, respectively. Yo, and Ykcal, were calculated from experimental values of Ysub, and from the elemental composition of bacterial cells. The dependence of the yield coefficients on the specific growth rate (μ) and maintenance coefficient (m) also was assessed. The analysis disclosed that m caused two- to threefold variations in the yield coefficients as μ was increased from 10% to 100% of μmax. The effect of different m values at constant specific growth rates also was determined. The value of m had a significant effect on the yield coefficients even at high specific growth rates. Assignment of cost factors to the yield coefficients provided an estimation of the impact m and μ on biomass production costs.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260150109
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  • 7
    Digitale Medien
    Digitale Medien
    A novel continuous centrifugal bioreactor for high-density cultivation of mammalian and microbial cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1190-1202 
    Details
    ISSN: 0006-3592
    Schlagwort(e): continuous centrifugal bioreactor ; ethanol fermentation ; mammalian cell hybridoma ; monoclonal antibody ; fluidized bed ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A continuous centrifugal bioreactor (CCBR), developed to study the growth and productivity of dense suspensions cultures, has been applied to both fermentation and mammalian cell cultivation processes. With this approach, high-density nonflocculent cultures are maintained in a tapered fluidized bed by balancing the drag forces on the cells due to following substrate with the centrifugal forces. The Sysyem was first used to produce ethanol by fermentation with Saccharomyces cerevisiae; then with H21A1 mouse hybridoma cells secreting monoclonal antibody (MoAb), lgM. Results of this research show the feasibility of using the CCBR for both production of secreted products and as a research tool for studying cell metabolism and production kinetics. Media recycle may be used to modify the behavior of the system form a plug flow apparatus to a continuous stirred reactor (CSTR).
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260381011
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  • 8
    Digitale Medien
    Digitale Medien
    Dialysis fermentation. II. Kinetic analysis of salicylic acid production via cell growth and maintenanceArticle No 4978, Michigan Agricultural Experiment Station. (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 12 (1970), S. 591-601 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A kinetic analysis was made of the relationship between salicylate production from naphthalene and growth of Pseudomonas fluorescens in semicontinuous dialysis culture. The specific rates both of product formation and growth initially were increased by the diffusional withdrawal of salicylate, but subsequently were reduced to low levels despite continued salicylate removal. Productivity and growth were correlated by the Luedeking-Piret equation in an initial nondialysis period and in the early stages of dialysis fermentation, when specific growth rates exceeded. 005 hr-1. Below this level of growth at later stages of dialysis fermentation, the specific production rate was correlated only with total cell mass by a proportionality constant of .035 hr-1, which was attributed to maintenance metabolism. Maintenance accounted for about 84% of the total salicylate produced, while growth-associated metabolism accounted for the remainder.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260120408
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  • 9
    Digitale Medien
    Digitale Medien
    Immobilization of a cephalosporin acetylesterase by containment within an ultrafiltration device (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 1033-1042 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A cephalosporin acetylesterase produced by Bacillus subtilis catalyzes the deacetylation of 7-aminocephalosporanic acid (7-ACA). Previous reports from our laboratory described the kinetic constants that characterize the reaction: Km = 2.8 × 10-3M, Kia acetate = 5 × 10-2M, and Kid deacetyl-7-ACA = 3.6 × 10-2M. These constants were used to predict the time course of the reaction using the following equation for dual competitive product inhibition. \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dS_t}}{{dt}} = \frac{{- V_{\max}}}{{1 + \left({K_m /S_t} \right)\left({1 + A_t /K_{{\rm ia}} + D_t /K_{{\rm id}}} \right)}} $$\end{document} where St = mg/ml 7-ACA, At = mg/ml acetate, Dt = mg/ml deacetyl-7-ACA. The predicted time course closely matched the time course measured experimentally. The equation also was solved without the inhibition terms and the solution indicated that product inhibition caused about a 30% increase in the time required for complete (〉97%) hydrolysis of a 24 mg/ml 7-ACA solution. The esterase was immobilized by containment within an ultrafiltration device. With this technique the enzyme was reused 20 times over an 11 day span to deacetylate 7-ACA solutions containing 4 to 24 mg/ml 7-ACA. The specific activity after the 20th use was the same as the activity prior to the first use, indicating little enzyme inactivation occurred.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260180802
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  • 10
    Digitale Medien
    Digitale Medien
    Prediction of the first normal stress difference in polymer solutions (1969)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 15 (1969), S. 643-653 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Shear stress and first normal stress difference data are presented for several polymer solutions undergoing steady shear rates from 1.0 to 100,000 sec.-1. The steady shear response is divided into three regions as a function of increasing shear rate. These are the diffusion controlled linear region, a moderate shear rate region where shear controls the entanglement-disentanglement process, and a high shear rate region where aggregation of polymer molecules occurs. The transitions between the three regions are clearly illustrated by using a group designated as the rotation rate function.A molecular model is derived for the shear controlled region that allows prediction of the first normal stress difference from the viscosity function and one additional constant that depends only on the molecular species. The White-Metzner equation is found to adequately describe the aggregation region at high shear rates.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690150505
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