ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Biochemistry and Biotechnology  (31)
  • Life and Medical Sciences  (5)
  • COMMUNICATIONS AND RADAR
  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1990-1994  (41)
  • 1
    Electronic Resource
    Electronic Resource
    Mass transfer characterization of an airlift probe for oxygenating and mixing cell suspensions in an NMR spectrometer (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 205-209 
    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 oxygen transfer characteristics of a 20-mm O.D. airlift contactor fitted with an oxygen microelectrode were determined by steady-state sulfite oxidation measurements. The volumetric mass transfer coefficient kLa was proportional to sparging power input per unit volume raised to a power which varied from 0.41 in water (coalescing bubbles) to 0.76 in NaCl solutions (noncoalescing bubbles). The highest observed kLa value was 0.012 s-1 which is sufficient to aerate Escherichia coli in an NMR spectrometer at moderate to high cell densities, depending on the physiological state of the cells.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370303
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Factors affecting bio-oxidation of sulfide minerals at high concentrations of solids: A review (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1164-1174 
    Details
    ISSN: 0006-3592
    Keywords: bio-oxidation ; high solids concentration ; rate limitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bio-oxidation has proved to be a viable process for the oxidative pretreatment of refractory gold-bearing sulfides. Generally, the oxidation rate is maximal at 20% solids for high sulfide content materials [ca. 30% sulfur]. Low grade ores [1% sulfur] have been successfully oxidized at 55% solids, indicating a link between the sulfide grade of the material and the optimal solids concentration for operation. Concentrations of high solids have been reported to lower oxidation rates, increase lag times, and decrease the ultimate extent of oxidation. This review discusses the various factors that have been proposed as causes of these phenomena. The factors include oxygen and carbon dioxide availability, low bacteria-solids ratio; mechanical damage or inhibition of the bacteria, inhibition of bacterial attachment, and the buildup of toxic leach products or other detrimental substances such as some flotation reagents. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260421006
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Overproduction of glycogen in Escherichia coli blocked in the acetate pathway improves cell growth (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 132-139 
    Details
    ISSN: 0006-3592
    Keywords: glycogen ; Escherichia coli ; cell growth ; acetate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Excessive production of acetate is a problem frequently encountered in aerobic high-cell-density fermentations of Escherichia coli. Here, we have examined genetic alterations resulting in glycogen overproduction as a possible means to direct the flux of carbon away from the acetate pool. Glycogen overaccumulation was achieved either by using a regulatory glgQ mutation or by transforming cells with a plasmid containing the glycogen biosynthesis genes glgC (encoding ADPG pyrophosphorylase) and glgA (encoding glycogen synthase) under their native promoter. Both strategies resulted in an approximately five-fold increase in glycogen levels but had no significant effect on acetate excretion. The glgC and glgA genes were then placed under the control of the isopropyl---D-thiogalactopyranoside (IPTG) inducible tac promoter, and this construct was used to stimulate glycogen production in a mutant defective in acetate biosynthesis due to deletion of the ack (acetate kinase) and pta (phosphotransacetylase) genes. If glycogen overproduction in the ack pta strain was induced during the late log phase, biomass production increased by 15 to 20% relative to uninduced controls. Glycogen overaccumulation had a significant influence on carbon partitioning: The output of carbon dioxide peaked earlier than in the control strain, and the levels of an unusual fermentation byproduct, pyruvate, were reduced. Exogenous pyruvate was metabolized more rapidly, suggesting higher activity of gluconeogenesis or the tricarboxylic acid (TCA) cycle as a result of glycogen overproduction. Potential mechanisms of the observed metabolic alterations are discussed. Our results suggest that ack pta mutants over producing glycogen may be a suitable starting point for constructing E. coli strains with improved characteristics in high-cell-density fermentations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440119
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Communication to the editor. Application of the cross-regulation system as a metabolic switch (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1190-1193 
    Details
    ISSN: 0006-3592
    Keywords: metabolic switch ; cross-regulation ; metabolic flux regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ability to switch metabolic flow from one pathway to another at a desired point in a bioprocess expands the horizons of metabolic engineering. Such an externally inducible switch can be realized by embedding synthetic operons behind tow corss-regulated promoters. This results in coordinated cessation of transcription of one operon while transcription of a second operon is simultaneously activated. The ability to effect such coordinated and inverse control of transcription of two operons has been illustrated experimentally using a model construct containing two different reporter genes, Vitreoscilla hemoglobin (VHb) and chloramphenicol acetyltransferase (CAT), fused to λPL and tac promoters, respectively, along with corresponding repressor genes in a cross-regulation configuration. Only VHb production was observed preinduction, and postinduction only CAT was produced. The framework presented here and its obvious extensions can be used with different combinations of promoter systems and synthetic operon constructs to achieve complicated metabolic flux regulation in diverse host. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431124
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Comparison of wild-type and Reg 1 mutant saccharomyces cerevisiae metabolic levels during glucose and galactose metabolism using 31P NMR (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 395-407 
    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 reg 1 mutation will allow the expression of a cloned gene on a plasmid under the control of a GAL promoter in the presence of glucose. The metabolism of wild-type and reg l mutant strains was examined by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Transient profiles of glucose 6-phosphate, fructose 6-phosphate, fructose 1, 6-diphosphate, and 3-phosphoglycerate indicated that glucose was processed differently for the reg 1 strain despite similar cytoplasrnic pH values and ATP levels. Intracellular phosphate became depleted in the transition to quasi-steady state and limited glycolysis in the reg 1 strain. The glucose uptake step or hexokinase step appears to be altered in the reg 1 strain. The reg 1 strain utilized galactose faster than the wild-type strain under the conditions used for NMR analysis. These results are consistent with the hypothesis that the REG 1 product operates early in the regulatory circuitry for glucose repression. This study illustrates the usefulness of transient information provided by NMR in understanding changes in the metabolism of genetically manipulated organisms.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350407
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Propagation of an amplifiable recombinant plasmid in Saccharomyces cerevisiae: flow cytometry studies and segregated modeling (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 565-577 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Efficient expression of a foreign protein product by the yeastSaccharomyces cerevisiaerequires a stable recombinant vector present at a high number of copies per cell. A conditional centromere yeast plasmid was constructed which can be amplified to high copy number by a process of unequal partitioning at cell division, followed by selection for increased copy number. However, in the absence of selection pressure for plasmid amplification, copy number rapidly drops from 25 plasmids/cell to 6 plasmids/cell in less than 10 generations of growth. Copy number subsequently decreases from 6 plasmids/cell to 2 plasmids/cell over a span of 50 generations. A combination of flow cytometric measurement of copy number distributions and segregated mathematical modeling were applied to test the predictions of a conceptual model of conditional centromereplasmid propagation. Measured distributions of plasmid content displayed a significant subpopulation of cells with a copy number of 4-6, evenin a population whose mean copy number was 13.5. This type of copy number distribution was reproduced by a mathematical model which assumes that amaximum of 4-6 centromere plasmids per cell can be stably partitionedat cell division. The model also reproduces the observed biphasic kinetics of plasmid number instability. The agreement between simulation and experimental results provides support for the proposed model and demonstrates the utility of the flow cytometry/segregated modeling approach for the study of multicopy recombinant vector propagation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350604
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Growing Saccharomyces cerevisiae in calcium-alginate beads induces cell alterations which accelerate glucose conversion to ethanol (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 417-426 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nongrowing Saccharomyces cerevisiae cells previously grown in alginate exhibit ethanol production rates 1.5 times greater than cells previously grown in suspension. Analysis of glucose, ethanol, and glycerol formation data using quasi-steady-state pathway stoichiometry shows that alginate-grown cells possess phosphofructokinase (PFK), ATPase, and polysaccharide synthesis maximum activities which are approximately two-, two-, and ninefold larger, respectively, than in suspension-grown cells. The estimated change in PFK maximum velocity is consistent with in vitro assays of PFK activity in extracts of suspension- and alginate-grown yeast. Estimation of ethanol production flux control coefficients using in vivo nuclear magnetic resonance (NMR) spectroscopy measurements of intracellular metabolite concentrations and a previously proposed detailed kinetic model of ethanol fermentation in yeast shows that glucose uptake dominates flux control in alginate-grown cells in suspension while earlier research revealed that PFK and ATPase exert significant flux control in suspension-grown cells. When placed in a calcium alginate matrix, alginate-grown cells produced ethanol 1.8 times more rapidly and accumulated substantially more polyphosphate than suspension-grown cells placed in alginate. Cells growing in alginate elicit responses at the genetic level which substantially alter pathway rates and flux control when these cells are used as either a suspended or an immobilized biocatalyst. These responses in gene expression to growth in alginate serve to reconfigure flux controls in alginate to a pattern which is similar to that obtained for suspended-grown cells in suspension.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260360413
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Influence of dilution rate and induction of cloned gene expression in continuous fermentations of recombinant yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 309-317 
    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 effects of growth rate on cloned gene product synthesis in recombinant Saccharomyces cerevisiae have been studied in continuous culture. The plasmid employed contains a yeast GAL10-CYC1 hybrid promoter directing expression of the E. coli lacZ gene. β-Galactosidase production was therefore controlled by the yeast galactose regulatory circuit, and the induction process and its effects were studied at the various dilution rates. At all dilution rates plasmid stability decreased with induction of lacZ gene expression. In some instances, two induced “steady states” were observed, the first 10-15 residence times after induction and the second after 40-50 residence times. The second induced steady state was characterized by greater biomass concentration and lower β-galactosidase specific activity relative to the first induced “steady-state.” β-Galactosidase specific activity and biomass concentration increased as dilution rate was reduced, and despite lower flow rate and plasmid stability, overall productivity (activity/L/hr) was substantially higher at low dilution rate. Important factors influencing all of the trends were the glucose and galactose (inducer) concentrations in the vessel and inducer metabolism.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370404
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Effect of alteration of the acetic acid synthesis pathway on the fermentation pattern of escherichia coli (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1318-1324 
    Details
    ISSN: 0006-3592
    Keywords: glucose metabolism ; pet operon ; E. coli ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The glucose metabolism of an Escherichia coli strain bearing mutations abolishing both acetyl phosphotransferase (PTA) and acetate kinase (ACK) activities was studied under aerobic and anaerobic conditions. These studies were conducted in a complex medium with the mutant carrying no plasmid, the mutant carrying the common cloning vector pUC19, and the mutant carrying a plasmid bearing the “pet” operon that encodes Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase activities. The mutant carrying no plasmid showed lower specific growth and glucose uptake rates relative to the parent wild-type strain (K-12), Lactic acid was produced at higher levels than the wild type, and considerable amounts of pyruvic acid were secreted as an unusual byproduct. Analysis of other fermentation products showed low but significant amounts of acetic acid, no accumulation of formic acid, and lower secretion of succinate and ethanol. The maintenance of the plasmid pUC19 in the mutant negatively affected metabolism. Expression of the pet operon overcame the metabolic stress caused by the plasmid, enhancing growth and glucose uptake rates to the values observed in the plasmidfree mutant. Also, expression of the pet operon allowed consumption of pyruvate accumulated during the first hours of fermentation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260381109
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Molecular design of expression systems: Comparison of different control configurations using molecular mechanism models (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 679-687 
    Details
    ISSN: 0006-3592
    Keywords: mathematical models ; cross regulation ; repressor synthesis control ; gene expression ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Molecular-level mathematical models have been used to evaluate the effectiveness of eight different configurations of repressor synthesis control on the regulation of cloned gene expression initiated from a promoter-operator sequence. Both single and dual-repressor situations were considered, employing genetically structured models for the lac and λPR promoter-operators in example calculations. Simulation results suggest that the most effective mode of cloned gene expression control is a cross-regulation configuration carried on a multicopy plasmid. This system was able to control cloned gene transcription in the uninduced state over a broad range of plasmid copy number and also provided the highest overall transcription rate in the induced state. The general strategies suggested by these simulations should be applicable for other repressor-operator-promoter systems in diverse hosts.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380702
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...