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  • 1
    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.
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  • 2
    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.
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  • 3
    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.
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  • 4
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A high butanol producing mutant strain of Clostridium acetobutylicum ATCC 4259 was obtained by chemical mutagenesis. Both mutant and parent strains were evaluated for butyrate uptake using the culture effluents of solventogenic fermentor-2 of the two-fermentor continuous system. Batch incubation of fermentor-2 culture effluents at 37 °C indicated lower butyrate uptake rates for mutant and parent strain, at 0.05 and 0.03 g l−1 h−1, respectively. Increased butyrate uptake rates of 0.33 and 0.26 g l−1 h−1 for mutant and parent strain, respectively, were observed when effluents were batch incubated at lower temperature of 30 °C. Butyrate conversion efficiency, at 5 ± 0.1 g l−1 of externally added butyrate, were 98.8% and 96.9% for mutant and parent strain, respectively. Butyrate up to the externally added concentration of 11.4 g l−1 did not inhibit butyrate uptake. The maximum butyrate consumption at a slightly reduced uptake rate was seen at 10.2 g l−1 butyrate concentration at 27 °C. Based on the results under different temperatures, the electron flow pattern has been computed and the mechanism for butyrate uptake has been hypothesized.
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  • 5
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of pH (between 4.4 and 6.6) on butyrate uptake by the mutant strain of Clostridium acetobutylicum was studied using the fermentation broth from fermentor-2 (solventogenic stage) of a two-fermentor continuous system. Low pH (〈 4.6) adversely affected the overall metabolic activity as observed by low solvent production and carbohydrate consumption. Uptake of 4.0 ± 0.5 g l−1 butyrate, under batch incubation at 30 °C, was not inhibited at pH 〉 5.2, however, at pH 〈 5.2, a marked inhibition in butyrate uptake was noticed. A higher pH (e.g. pH 5.4) was required for the uptake of elevated concentration of externally added butyrate at 8.5 ± 1.0 g l−1. Batch incubation at relatively higher temperatures (35° and 37 °C) indicated a similar trend i.e., a pH of 〉5.5 was required for uptake of 〉8 g l−1 butyrate. Optimization studies for butyrate uptake by C. acetobutylicum suggested a direct correlation between minimum pH and butyrate concentration or temperature. The role of undissociated butyric acid appears to be critical in regulation of butyrate uptake.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 4 (1982), S. 19-22 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Agricultural residues such as bagasse and rice straw have been hydrolyzed by mixed culture filtrates of T. reesei and A. wentii to obtain fermentable sugars. After the hydrolyzate had been treated to remove undesired impurities, Cl. saccharoper butylacetonicum was used to produce butanol to the extent of 16 g/l.
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