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  • 1
    Electronic Resource
    Electronic Resource
    Use of a fluorescein derivative of phosphatidylethanolamine as a pH probe at water/lipid interfaces
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 939 (1988), S. 289-294 
    Details
    ISSN: 0005-2736
    Keywords: Fluorescent indicator ; Phosphatidylethanolamine ; Water/lipid interface ; pH probe
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(88)90073-9
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  • 2
    Electronic Resource
    Electronic Resource
    Modelling of continuous acetonobutylic fermentation (1992)
    Springer
    Bioprocess and biosystems engineering 7 (1992), S. 357-361 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A model of continuous acetonobutylic fermentation is proposed. This model correctly portrays the predominantly solvents formation observed at acidic extracellular pH and predominantly acids production at more neutral pH, as well as observed effects of dilution rate and feed substrate on products' concentrations. A fair agreement between experimental and theoretical predictions is achieved for a broad range of operating variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369491
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of continuous fermentation processes in aqueous two-phase systems (1992)
    Springer
    Bioprocess and biosystems engineering 7 (1992), S. 315-317 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Simulations of continuous ethanol or acetonobutylic fermentations in aqueous two-phase systems show that at high substrate feed concentrations it is possible to obtain solvent productivities about 25–40% higher than in conventional systems with cell recycle if the biomass bleed rate is kept about one tenth of the value of D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705161
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  • 4
    Electronic Resource
    Electronic Resource
    Bubble free gaseous transfer in bioreactors using perfluorocarbons (1995)
    Springer
    Bioprocess and biosystems engineering 13 (1995), S. 293-300 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this work the concept of bubble-free oxygenation that was able to ensure oxygen supply and carbon dioxide extraction for a chemostat culture of Escherichia coli was experimentally demonstrated. It was operated at the dilution rate of 0.275 h−1 under atmospheric pressure and at 35.5 °C. Foralkyl, a commercial perfluorocarbon, added in the influent medium under emulsified form and at 50% volumic fraction, was able to provide 0.17 g O2/l/h and extract 0.23 g CO2/l/h for a culture at 0.74 g/l of biomass. This oxygen supply was close to the maximum oxygenation Foralkyl was theoretically able to provide at this pressure when imposing a minimum oxygen concentration of 1 mg/l in the water phase. The quantification of transfer was not done from a direct measurement of oxygen transfer rates because conventional oxygen concentration measurement by membrane polarographic probe in an emulsion was not judged reliable. This evaluation was done by referring to conventional aerated culture whose measurable parameters (biomass and product concentrations) were found unaffected when shifting to the novel oxygenation device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369560
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  • 5
    Electronic Resource
    Electronic Resource
    Continuous acetone-butanol fermentation: a global approach for the improvement in the solvent productivity in synthetic medium (1987)
    Springer
    Applied microbiology and biotechnology 25 (1987), S. 317-321 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The present chemostat culture studies were performed in a partial gas recycle system using Clostridium acetobutylicum ATCC 824. Initiation of chemostat cultures at two different levels of vitamins has demonstrated a more than 3 fold improvement in the solvent productivity. The production of extracellular autobacteriocin was increased markedly, when strict anaerobic conditions of the feed vessel were not maintained. When pH was regulated at 4.4, very little variation was seen in the concentration of acids. The duration of solvent production was reduced significantly when NH4OH was replaced by NaOH for pH regulation, whereas a marked increase in the production of extracellular autobacteriocin was observed. In the optimised medium conditions, a solvent productivity of 2.09 g l-1 h-1 (highest ever) could be obtained in the synthetic medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252540
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  • 6
    Electronic Resource
    Electronic Resource
    Continuous acetone-butanol fermentation: influence of vitamins on the metabolic activity of Clostridium acetobutylicum (1987)
    Springer
    Applied microbiology and biotechnology 27 (1987), S. 1-5 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A detailed investigation was undertaken to examine the influence of biotin and paminobenzoic acid (PABA) in chemostat cultures of Clostridium acetobutylicum ATCC 824. Initiation of chemostat cultures with a basic synthetic medium (biotin 0.01 mg l−1; PABA 1.0 mg l−1) have resulted in a low biomass together with a low specific rate of solvent production. A different picture emerged on elevating the concentration of both vitamins 8-fold: biomass and specific rates (solvent production, glucose consumption) were increased and a solvent productivity of 2.54 g l−1 h−1 at the solvent concentration of 13.1 g l−1 was achieved. It has also been shown that PABA was the only limiting factor for the metabolism of Clostridium acetobutylicum in the basic synthetic medium and that the optimised concentration was 8 mg l−1 in the chemostat cultures with the growth conditions employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257244
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  • 7
    Electronic Resource
    Electronic Resource
    Metabolic flexibility of Clostridium acetobutylicum in response to methyl viologen addition (1994)
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 611-616 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Batch cultures of Clostridium acetobutylicum, were examined with 0, 0.1 and 1 mM methyl viologen addition at four different controlled pH values (between 4.5 and 6.5). Methyl viologen addition diverted the electron flow: reducing equivalents normally released as molecular hydrogen were directed towards NAD(P)H formation. Production of butanol, the most reduced non-gaseous product, was sharply increased (0.65 mol/mol glucose) at the expense of acetone and butyric and acetic acids. In addition to butanol and lactate production, NADH excess induced the formation of glycerol, a product that has never been reported to be formed by C. acetobutylicum. Metabolic perturbation brought about by the electron carrier led to a reduction of the growth rate and an increase of the lag phase. A correlation between the shape of the redox potential curve and the switch from an acidogenic to a solventogenic metabolism is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173928
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  • 8
    Electronic Resource
    Electronic Resource
    Solvent production from starch: effect of pH on α-amylase and glucoamylase localization and synthesis in synthetic medium (1992)
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 539-543 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The fermentation of starch by Clostridium acetobutylicum ATCC 824 has been reviewed in an optimised synthetic medium. A progressive increase of pH from 4.4 to 5.2 led to a higher production of extracellular α-amylase whereas glucoamylase was poorly affected. A portion of these enzymes was cell-associated and on increasing the pH from 4.4 to 5.8 a decrease was noted in cell-bound enzymes. The association was higher for the glucoamylase than for the α-amylase. The highest rate of starch consumption was at pH 5.2 whereas due to the earlier shift to solvent production at low pH, the highest solvent production was at pH 4.4. This study suggested that the level of α-amylase and then the rate of starch hydrolysis was the limiting step of sugar catabolism in C. acetobutylicum ATCC 824.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240721
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  • 9
    Electronic Resource
    Electronic Resource
    Inactivation of lytic enzymes by heat treatment in ultrafiltration-coupled acetonobutylic fermentation (1990)
    Springer
    Applied microbiology and biotechnology 33 (1990), S. 274-279 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Clostridium acetobutylicum cultures were grown in batch mode, using mineral ultrafiltration membranes to confine the microbial cells in the fermentor while the permeate was subject to heat treatment (70° C for 20 min) before recycling. The extracellular lytic activity in the broth, measured by the initial rate of lysis of a buffered suspension of Clostridium cell walls, was strongly decreased by a factor of 6.7 at pH 5.5, and 3.9 at pH 4.8. This caused an enhancement of the growth rate during the course of fermentation and an increase in the maximal cell concentration, which was practically doubled in heat-treatment assays. The solvent production results obtained were less positive in terms of productivity and final butanol concentration, since there was no significant improvement, despite elimination of lytic enzyme inhibition. The heat-inactivation of lytic enzymes influenced the culture more than the suppression of product inhibition, particularly concerning the activity and orientation of this bacterial metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164521
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  • 10
    Electronic Resource
    Electronic Resource
    Metabolic flexibility of Clostridium acetobutylicum in response to methyl viologen addition (1994)
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 611-616 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Batch cultures of Clostridium acetobutylicum, were examined with 0, 0.1 and 1 mM methyl viologen addition at four different controlled pH values (between 4.5 and 6.5). Methyl viologen addition diverted the electron flow: reducing equivalents normally released as molecular hydrogen were directed towards NAD(P)H formation. Production of butanol, the most reduced non-gaseous product, was sharply increased (0.65 mol/mol glucose) at the expense of acetone and butyric and acetic acids. In addition to butanol and lactate production, NADH excess induced the formation of glycerol, a product that has never been reported to be formed by C. acetobutylicum. Metabolic perturbation brought about by the electron carrier led to a reduction of the growth rate and an increase of the lag phase. A correlation between the shape of the redox potential curve and the switch from an acidogenic to a solventogenic metabolism is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050301
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