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  • Chemistry  (2)
  • Amino Acyl-tRNA Synthetases/chemistry
  • 1995-1999  (2)
  • 1996  (2)
  • 1
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Permeations- und Trennungseigenschaften von Poly[bis(2,2,2-trifluoroethoxy)-phosphazene]-(PBTFP)-Membranen wurden durch Pervaporation und Evapomeation von wäßrigen Methanol-Lösungen und Ethanol-Lösungen untersucht. Bei der Pervaporation permeierten vorwiegend Methanol bei allen Mischungsverhältnissen und Ethanol bei Mischungen mit geringem Ethanolgehalt. Wasser permeierte bevorzugt bei Ethanol/Wasser-Mischungen mit höheren Ethanolkonzentrationen. Bei der Evapomeation durchdrang Wasser bei allen Dampfkonzentrationen der wanrigen Methanol-und Ethanol-Liisungen selektiv die Membran. Diese verschiedenen Permeationsselek-tivitäten hingen von den Mischungsverhaltnissen ab. Die Techniken der Membranen-permeation wurden bei unterschiedlichen Permeations- und Trennungsmechanismen diskutiert. Es wurde festgestellt, daß die Permeationsgeschwindigkeit vom Quellungsgrad der PBTFP-Membranen beeinflurßt wird und sich die Permeationsselektivitat von Wasserdampf aus alkoholischen Esungen mit zunehmendem Quellungsgrad der Membranen erhoht. Während der Einfluß steigender Permeationstemperaturen auf den Quellungsgrad der Membranen gering ist, nehmen Permeationsgeschwindigkeit und Permeationsselektivitat von Alkohol bei Pervaporation und Evapomeation mit steigenden Permeationstemperaturen starker zu. Die Ergebnisse werden hinsichtlich der Struktur der PBTFP-Membranen bei Pervaporation und Evapomeation diskutiert.
    Notes: The characteristics of permeation and separation for aqueous solutions of methanol and ethanol through a poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PBTFP) membrane were studied by pervaporation and evapomeation. In pervaporation technique, methanol was preferentially permeated in all of the feed solution compositions and ethanol was permeated in lower ethanol concentrations of the feed solution. Water was predominantly permeated from the feed solutions with higher ethanol concentration. In evapomeation technique, water was selectively permeated in both all of the feed vapor compositions for aqueous methanol and ethanol solutions. These different permselectivities depended on the feed composition and the membrane permeation technique and could be discussed by a difference in the mechanisms of permeation and separation. It was found that the permeation rate was influenced remarkably by the degree of swelling of the PBTFP membrane and the permselectivity for water of aqueous alcoholic solutions was enhanced by an increasing degree of swelling of the membrane. When the degree of swelling of the membrane with rising permeation temperature was small, both the permeation rate and permselectivity for alcohol in pervaporation and evapomeation increased with the permeation temperature. The above results are discussed considering the PBTFP membrane structure in evapomeation and pervaporation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3592
    Keywords: Streptomyces virginiae ; autoregulator ; virginiae butanolide ; virginiamycin fermentation ; optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A strategy for optimization of non-growth-associated production in batch culture employing an empirical approach was developed through the study of virginiamycin production. The strategy is formulated with two aims: attaining a high cell concentration at the beginning of the production phase without decrease in production activity; and enhancing the production activity during the production phase. As a practical example, the goal of a maximum virginiamycin (M and S) production in the batch culture of Streptomyces virginiae was set. To attain a high cell concentration in the production phase of the batch culture, that is, to extend the growth phase for as long as possible, the optimum composition and concentration of the complex medium, especially the yeast extract (YE) concentration, were first investigated. Dissolved oxygen (DO) concentration control was also a parameter considered in maintaining the production activity during the production phase. In addition, to enhance the production activity, an optimum addition strategy of an autoregulator, virginiae butanolide-C (VB-C), was investigated. Combining these measures, the optimum cultivation conditions were found to be an initial YE concentration in the complex medium of 45 g/L, the shot addition of 300 μg/L of VB-C 11.5 h after the start of the batch culture, and a DO concentration maintained above 2 mg/L. The maximum concentrations of virginiamycin M and S were about ninefold those obtained under nonoptimum cultivation conditions. Nonoptimum cultivation conditions consisted of an initial YE concentration one sixth (7.5 g/L) that of the optimum cultivation conditions, and no VB-C addition. These conditions were used as representative of the standard cultivation of virginiamycin in this study. The strategy developed here will be applicable to the production of other antibiotics, especially to the cultivation of Streptomyces species, in which a hormonelike signal material (an autoregulator) plays an important role in antibiotic production. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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