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  • 1
    Electronic Resource
    Electronic Resource
    Cultivation of Saccharomyces cerevisiae in continuous culture (1972)
    Springer
    Archives of microbiology 83 (1972), S. 347-358 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Growth of Saccharomyces cerevisiae was investigated under aerobic conditions in a glucose limited chemostat. The steady state concentrations of cells, glucose and ethanol were measured in dependence of the dilution rate. The growth rate showed a biphasic dependence from the glucose concentration. A shift from respiratory to fermentative metabolism (Crabtree-effect) altering heavily the cell yield and the ethanol yield took place in the range of dilution rates between 0.3 h-1 and 0.5 h-1. Therefore the classical theory of continuous cultures is not applicable on aerobic growth of Saccharomyces cerevisiae under glucose limitation without introducing further premises. On the other hand the steady state cell concentration as a function of the dilution rate fits well the theoretically calculated curves, if cells are cultivated under conditions where only fermentation or respiration is possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425247
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  • 2
    Electronic Resource
    Electronic Resource
    Cultivation of Saccharomyces cerevisiae in continuous culture (1971)
    Springer
    Archives of microbiology 79 (1971), S. 176-186 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Glucose limited growth of a respiratory deficient mutant of Saccharomyces cerevisiae was studied in continuous culture under steady state conditions. The maximal growth rate, the Michaelis constant, the cell yield, the maintenance coefficient and the ethanol yield of the growing cell population were determined. The steady state concentrations of cells, glucose and ethanol were measured as functions of the dilution rate and compared with theoretical predictions. A far-reaching agreement between theory and experiment was observed. The decrease of the cell yield in the range of low dilution rates is well explained by introducing the concept of maintenance energy in the general theory of continuous cultures. A deviation of the cell yield from the predicted values, which has been found in the range of high dilution rates, is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00424924
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  • 3
    Electronic Resource
    Electronic Resource
    Albumin Nanospheres as Carriers for Passive Drug Targeting: An Optimized Manufacturing Technique (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 32-37 
    Details
    ISSN: 1573-904X
    Keywords: albumin ; nanospheres ; manufacturing ; glutaraldehyde ; cross-linking ; central composite design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to develop a new method to produce albumin particles in the sub-200-nanometer range with a narrow size distribution and in a controlled and reproducible manner. Methods. A new emulsion crosslinking method was developed using ultrasound and static mixing as homogenization steps and a central composite design was used to evaluate the influence of different process parameters on particle size, polydispersity and yield. Results. Response surface analysis allowed the location of the most important factors. Of all the factors investigated, only the albumin concentration and the aqueous phase volume showed a significant influence on response parameters. Albumin nanospheres with sizes below 200 nm in diameter and very narrow size distributions were obtained in high yields (〉80%). Conclusions. This study describes a new preparation method for albumin nanoparticles which are suitable for future drug targeting studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016064930502
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of Drug/Plasma Protein Interactions by Means of Asymmetrical Flow Field-Flow Fractionation (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 1706-1712 
    Details
    ISSN: 1573-904X
    Keywords: asymmetrical flow field-flow fractionation ; FFF ; plasma proteins ; HAS ; lipoproteins ; N-Benzoyl-staurosporine ; recovery ; separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The applicability of Asymmetrical Flow Field-Flow Fractionation (Asymmetrical Flow FFF) as an alternative tool to examine the distribution of a lipophilic drug (N-Benzoyl-staurosporine) within human plasma protein fractions was investigated with respect to high separation speed and loss of material on surfaces due to adsorption. Methods. Field-Flow Fractionation is defined as a group of pseudo-chromatographic separation methods, where compounds are separated under the influence of an externally applied force based on differences in their physicochemical properties. This method was used to separate human plasma in its protein fractions. The drug distribution in the fractions was investigated by monitoring the fractionated eluate for drug content by fluorescence spectroscopy. Results. Human plasma was separated into human serum albumin (HSA), high density lipoprotein (HDL), α2-macroglobulin and low density lipoprotein (LDL) fractions in less than ten minutes. Calibration of the system and identification of the individual fractions was performed using commercially available protein reference standards. The influence of membrane type and carrier solution composition on the absolute recovery of N-Benzoyl-staurosporine and fluorescein-isothio-cyanate-albumin (FITC-albumin) was found to be quite significant. Both factors were optimized during the course of the investigations. N-Benzoyl-staurosporine was found to be enriched in the fraction containing HSA. Conclusions. If experimental conditions are thoroughly selected and controlled to suppress drug and plasma protein adsorption at the separation membrane, Asymmetrical Flow FFF shows high recoveries and fast separation of human plasma proteins, and can be a reliable tool to characterize drug / plasma protein interactions. For analytical purposes it has the potential to rival established technologies like ultracentrifugation in terms of ease-of-use, precision, and separation time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012171511285
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  • 5
    Electronic Resource
    Electronic Resource
    Fundamentals of Powder Compression. I. The Compactibility and Compressibility of Pharmaceutical Powders (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 12-22 
    Details
    ISSN: 1573-904X
    Keywords: powder compression ; compression equations ; compactibility ; compressibility ; compression equations ; compact hardness tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In spite of the widespread use of tablets, the theoretical understanding of the tableting process has been limited. During the last decades considerable research has been done in the field of powder technology and compaction. A survey of the literature and compression equations reveals many studies on the characterization of powder properties, most of which relate to volume reduction under pressure, i.e., to the compressibility of the powder bed. For practical purposes, however, it is also important to know the compactibility of a powder bed, i.e., the ability of a powdered material to be compressed into a compact of specified strength. This strength has to be defined, e.g., as radial tensile strength or deformation hardness. Thus the first part of this review comprises the theory of powder compression of individual substances, compression parameters, compression equations, and mechanical properties of compacts, including compact strength tests and compact hardness tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016364613722
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  • 6
    Electronic Resource
    Electronic Resource
    The Use of Fluorescence Resonance Energy Transfer to Study the Disintegration Kinetics of Liposomes Containing Lysolecithin and Oleic Acid in Rat Plasma (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 1118-1123 
    Details
    ISSN: 1573-904X
    Keywords: Fluorescence Resonance Energy Transfer (RET) ; liposomes ; lysolecithin ; blood plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To validate Fluorescence Resonance Energy Transfer (RET) as method to monitor disintegration of fluorescently labeled liposomes varying in lysolecithin/oleic acid (equimolar) content, lysolecithin fatty acid composition and vesicle size in rat blood plasma and buffer. Methods. NBD-PE and Rho-PE were used for RET. The measurements were performed on a Perkin Elmer LS-50 spectrofluorimeter. Liposomes were prepared by the extrusion method. Results. Analysis of the RET data was optimised using a fitting procedure to correct for fluorescence interference by plasma. The disintegration patterns of liposomes could be described by a bi-exponential decay model. Disintegration rate increased at increasing lysolecithin/oleic acid content and decreasing size. In contrast, all liposomes showed no disintegration in buffer. Conclusions. RET is a suitable method to monitor liposome disintegration in non-diluted plasma. Rate and extent of liposome disintegration increases at decreasing liposome size and increasing lysolecithin/oleic acid content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026413914687
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  • 7
    Electronic Resource
    Electronic Resource
    Fundamentals of Powder Compression. II. The Compression of Binary Powder Mixtures (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 65-74 
    Details
    ISSN: 1573-904X
    Keywords: compression ; compressibility ; compactibility ; binary powder mixtures ; additivity rules ; strength of a compact ; sticking ; capping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Although tablet formulations are multicomponent systems, there have been only a few studies on the compression of binary or ternary powder mixtures. Physical interactions between the individual components may influence important biopharmaceutical properties of the compact, e.g., disintegration time and dissolution rate of the active ingredient. In the second part of this review paper the importance of these physical interactions is emphasized. The investigations are limited to the strength of the compact. An attempt is made to deduce additivity rules for the material-specific compressibility and compactibility parameters. Such additivity rules are of special importance, as they may allow the prediction of tablet properties at the formulation test. The final section is devoted to problems in compression, i.e., sticking and capping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016333101427
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  • 8
    Electronic Resource
    Electronic Resource
    Screening for microorganisms performing the stereoselective reduction of α-formyl-esters (1985)
    Springer
    Applied microbiology and biotechnology 22 (1985), S. 208-210 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary 107 Microorganisms selected from 26 genera belonging to bacteria, actinomycetes, fungi and yeasts were screened for their ability to reduce α-formyl-esters stereoselectively. Eighteen strains have been found which were able to reduce at least one of 5 substrates tested with an optical purity of more than 85% ee. The best strains were Candida humicola, Aspergillus petrakii, Streptomyces hydrogenans and Streptomyces griseus. The dependence of the enantioselectivity of the reduction on the group of microorganisms and on the substituents of the formyl-esters is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253611
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  • 9
    Electronic Resource
    Electronic Resource
    Asymmetric microbial reduction of ethyl and isoprophyl α,1,3-trioxo-2-isoindolinebutyrate (1990)
    Springer
    Applied microbiology and biotechnology 32 (1990), S. 533-537 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Microorganisms are capable of the asymmetric reduction of various types of ketones. From a limited screening with 103 selected microbial strains two have been chosen which reduce ethyl and isopropyl α,1,3-trioxo-2-isoindolinebutyrate (1a and 1b) stereoselectively. The optically active products ethyl and isopropyl α-hydroxy-1,3-dioxo-2-isoindoline butyrate (2a and 2b) are useful precursors of the cerebral insufficiency improver hydroxy-aniracetam. Up to 3% of substrates 1a or 1b can be added in the reaction medium and converted by Candida parapsilosis. The isolated (R)-enantiomers of the product alcohols 2a and 2b show an enantiomeric excess (ee) of 98%–99%. The process was successfully tested on a 200-1 scale, the transformation rate being 0.83 g/1 per day and the yield of isolated product 72%. With Torulopsis magnoliae (S)-enantiomers of the products 2a and 2b were formed with an ee of 97%–99%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173723
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  • 10
    Electronic Resource
    Electronic Resource
    Focus on Research in Nanoscience and Nanotechnology in Switzerland (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 391-392 
    Details
    ISSN: 1572-896X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010016515898
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