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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 217 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A large cellulosomal gene cluster was identified in the recently sequenced genome of Clostridium acetobutylicum ATCC 824. Sequence analysis revealed that this cluster contains the genes for the scaffolding protein CipA, the processive endocellulase Cel48A, several endoglucanases of families 5 and 9, the mannanase Man5G, and a hydrophobic protein, OrfXp. Surprisingly, genetic organization of this large cluster is very similar to that of Clostridium cellulolyticum, the model of mesophilic clostridial cellulosomes. As C. acetobutylicum is unable to grow on cellulosic substrates, the existence of a cellulosomal gene cluster in the genome raises questions about its expression, function and evolution. Biochemical evidence for the expression of a cellulosomal protein complex was investigated. The results of sodium dodecyl sulfate–polyacrylamide gel electrophoresis, N-terminal sequencing and Western blotting with antibodies against specific components of the C. cellulolyticum cellulosome suggest that at least four major cellulosomal proteins are present. In addition, despite the fact that no cellulolytic activities were detected, we report here the evidence for the production of a high molecular mass cellulosomal complex in C. acetobutylicum.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 210 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Clostridium acetobutylicum produces an extracellular α-amylase when grown on glucose as the sole carbon source. This enzyme was previously characterized from a biochemical point of view but its encoding gene was never identified. The 2283-bp amyP gene encodes a 83 013-Da mature protein with an N-terminal domain that exhibits strong identity to the family 13 glycosyl hydrolases such as the Bacillusα-amylases. Transcriptional analysis revealed that amyP is transcribed in solventogenic but not in acidogenic chemostat cultures. These results are in agreement with the extracellular α-amylase activities indicating that the expression of amyP is regulated at the transcriptional level. amyP is located on the pSOL1 megaplasmid that carries all the genes involved in the final steps of solvent formation. Degeneration of C. acetobutylicum has been associated to the loss of pSOL1. We demonstrate here that amyP can be used as a reporter system to quantitatively follow this phenomenon.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 799 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 17 (1995), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Alcohol formation was initiated in continuous cultures of Clostridium acetobutylicum under distinct steady-state conditions: (i) in glucose-limited cultures established at low operating pH with formation of butanol, ethanol and acetone (induction of the solventogenesis) in which cells contained normal levels of NADH and a high level of ATP and butyric acid; and (ii) by increasing the NADH pressure at neutral pH in glucose-limited cultures after addition of Neutral red, or in glucose-glycerol or glucose-glycerol-pyruvate grown cultures, with a strictly alcohologenic metabolism (no acetone produced) associated with high levels of intracellular NADH and various levels of ATP. These two different metabolic shift systems are correlated with the expression of different genes involved in the solvent-forming pathways and the electron flow distribution. A high NADH level leading to butanol and ethanol formation was accompanied by increased activities of the NADH-dependent alcohol and butyraldehyde dehydrogenases, and ferredoxin:NAD(P)+ reductases, and by decreased activities of the NADH:ferredoxin reductase. This last group of enzymes constitutes the key enzymes regulating electron flow, since no change in hydrogenase activity was observed. On the other hand, classical solventogenesis appears to be characterized by high levels of expression of the NADPH-dependent alcohol and butyraldehyde dehydrogenases, and of the two enzymes involved in the acetone-forming pathway, while the ferredoxin:NAD(P)+ reductases were not synthesized. A decrease of the in vitro hydrogenase activity explains the lower hydrogen generation. In addition, the regulation of the intracellular pH was different between the alcohologenic culture grown at neutral pH and the solventogenic cultures grown at low pH. An inversion of the transmembrane pH gradient was observed during the production of alcohol at neutral pH and was related to a lower in vivo specific rate of hydrogen production while in the cultures grown at low pH the transmembrane pH generation was not linked to the F1F0 ATPase activity.
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  • 5
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: The metabolism of Clostridium acetobutylicum was manipulated, at neutral pH and in chemostat culture, by the addition of Neutral red, a molecule that can replace ferredoxin in the oxido-reduction reactions catalysed by the enzymes involved in the distribution of the electron flow. Cultures grown on glucose alone produced mainly acids while cultures grown on glucose plus Neutral red produced mainly alcohols and butyrate and low levels of hydrogen. We demonstrated that just after addition of Neutral red to an acidogenic culture, the simultaneous utilizations of ferredoxin and dye deviate electron flow from hydrogen to NADH production initially by the enzymatic regulation of in vivo hydrogenase and ferredoxin NAD reductase activities. The higher NAD(P)H pool generated might, thereafter, be the signal for the setting up of a new metabolism. In the resulting steady-state, the NAD(P)H ‘pressure’ is maintained by high ferredoxin NAD and NADP reductases level associated to a low NADH ferredoxin reductase level. The regeneration of NAD is mainly achieved via the induced or increased NADH-dependent aldehyde and alcohol dehydrogenase activities.
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 489-489 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - The Weizmann process1, in which the bacterium Clostridium acetobutylicum converts corn starch into acetone and butanol, was used during the First World War to produce the acetone needed for smokeless gunpowder. The loss of the Weizmann strain's capacity to produce solvents after repeated ...
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 179-183 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The inhibitory effect of various alkanols, benzyl alcohol and phenethyl alcohol on the growth rate of Clostridium acetobutylicum ATCC 824 was investigated. Inhibition of cell growth was studied by treating cultures with varied concentrations of alcohols. There was a threshold concentration above which growth inhibition occurred. The degree of inhibition was a linear function of the alcohol concentration used. The natural logarithm of the inhibition constant was shown to be: (1) a linear function of the chain length of the alkanols, (2) a linear function of the natural logarithm of the octanol/water partition coefficient for both aliphatic and cyclic alcohols.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 714-717 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A mathematical model of batch acetonobutylic fermentation under glucose limitation is proposed. Making use of available information on the physiology of the process this model correctly predicts the two phases of growth and product formation observed at low extracellular pH, with production of butanol and acetone predominating in the final stage and butyrate and acetate production predominating at more neutral pH. A fair agreement between the prediction and experiments performed in different laboratories at different substrate concentrations and pH was achieved.
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  • 9
    ISSN: 0006-3592
    Keywords: glycerol ; Enterobacter agglomerans ; 3-hydroxypropionaldehyde ; catabolic limitation ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch fermentation of glycerol to 1,3-propanediol (1,3PPD) by Enterobacter agglomerans CNCM 1210 showed the lethal accumulation of 3-hydroxypropionaldehyde (3-HPA) when performed under initial substrate content higher than 40 g/L. Assigned to the inhibition by the NAD/NADH ratio of the 3-HPA converting enzyme: 1,3PPD dehydrogenase, intracellular assays were conducted in an attempt to identify the metabolic mechanisms involved in the increase of that ratio. An overflow metabolism through the 1,3PPD formation pathway was established, while a catabolic limitation in the oxidative branch at the level of glyceraldehyde-3-phosphate dehydrogenase occurred. Uncoupled activities of synthesis and consumption of reducing equivalents are thus suspected to provoke the increase of the NAD/NADH ratio and the subsequent accumulation of 3-HPA. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:303-305, 1998.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 342-348 
    ISSN: 0006-3592
    Keywords: Clostridium acetobutylicum ; chemostat culture ; potentiostatic system ; methyl viologen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The metabolism of Clostridium acetobutylicum was manipulated in chemostat culture at pH 5 and 6.5 in a three-electrode potentiostatic system with methyl viologen (MV) as the electron carrier. When a constant potential was applied at pH 5, the broth redox potential continuously decreased and, simultaneously, a high increase in the reduced MV concentration (MV+.) and the specific rate of butanol production was observed while butyric acid was taken up. A linear relationship was reported between the specific rate of NAD(P)+ reduction by ferredoxin-NAD(P)+ reductase and the broth redox potential, as long as the growth rate was not affected. To reach a steady state in glucose limited culture, a control system of the redox potential was required. However, it seems that C. acetobutylicum is able to adapt its metabolism when the broth redox potential was regulated at low value. On the other hand, at pH 6.5, the current generated by the electrochemical device had no effect either on broth redox potential and MV+. concentration or on the metabolism. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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