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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 24 (2000), S. 277-284 
    ISSN: 1476-5535
    Keywords: Keywords: polycyclic aromatic hydrocarbons; creosote; bioremediation; bioaugmentation; biodegradation; inoculum preparation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Creosote was evaluated as an inexpensive carbon source for growing inocula of a polycyclic aromatic hydrocarbon (PAH)-degrading bacterial community (community five). Creosote was a poor growth substrate when provided as sole carbon source in a basal salts solution (BSM). Alternatively, peptone, yeast extract or glucose in BSM supported high growth rates, but community five could not subsequently degrade pyrene. A combination of creosote and yeast extract in BSM (CYEM) supported growth and maintained the pyrene-degrading capacity of community five. Optimum pyrene-degrading activity occurred when the inocula were grown in creosote and yeast extract concentrations of 2 ml L−1 and 1 g L−1 respectively: concentrations outside these values resulted in either low biomass yields or loss of PAH-degrading activity. CYEM-grown community five inocula degraded 250 mg L−1 of pyrene in BSM at a rate comparable to cultures inoculated with community five grown in BSM-pyrene. However, the CYEM-grown community showed a 40% lower rate of PAH degradation in a synthetic PAH mixture compared with pyrene-grown cells and there was an increase in the lag period before the onset of PAH degradation. This appears to reflect a weaker induction of PAH catabolism by CYEM compared to BSM-pyrene. Journal of Industrial Microbiology & Biotechnology (2000) 24, 277–284.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 23 (1999), S. 701-708 
    ISSN: 1476-5535
    Keywords: Keywords: ethanol; recombinant; E. coli KO11; lignocellulosic; chemostat; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differing claims regarding the stability of the recombinant ethanologen E. coli KO11 are addressed here in batch and chemostat culture. In repeat batch culture, the organism was stable on glucose, mannose, xylose and galactose for at least three serial transfers, even in the absence of a selective antibiotic. Chemostat cultures on glucose were remarkably stable, but on mannose, xylose and a xylose/glucose mixture, they progressively lost their hyperethanologenicity. On xylose, the loss was irreversible, indicating genetic instability. The loss of hyperethanologenicity was accompanied by the production of high concentrations of acetic acid and by increasing biomass yields, suggesting that the higher ATP yield associated with acetate production may foster the growth of acetate-producing revertant strains. Plate counts on high chloramphenicol-containing medium, whether directly, or following preliminary growth on non-selective medium, were not a reliable indicator of high ethanologenicity during chemostat culture. In batch culture, the organism appeared to retain its promise for ethanol production from lignocellulosics and concerns that antibiotics may need to be included in all media appear unfounded.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 24-29 
    ISSN: 0006-3592
    Keywords: acetaldehyde ; intracellular accumulation ; inhibition ; transport ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of acetaldehyde efflux from yeast cells and its intracellular concentration were studied in the light of recent suggestions that acetaldehyde inhibition may be an important factor in yeast ethanol fermentations. When the medium surrounding cells containing ethanol and acetaldehyde was suddenly diluted, the rate of efflux of acetaldehyde was slow relative to the rate of ethanol efflux, suggesting that acetaldehyde, unlike ethanol, may accumulate intracellularly. Intracellular acetaldehyde concentrations were measured during high cell density fermentations, using direct injection gas chromatography to avoid the need to concentrate or disrupt the cells. Intracellular acetaldehyde concentrations substantially exceeded the extracellular concentrations throughout fermentation and were generally much higher than the acetaldehyde concentrations normally recorded in the culture broth in ethanol fermentations. The technique used was sensitive to the time taken to cool and freeze the samples. Measured intracellular acetaldehyde concentrations fell rapidly as the time taken to freeze the suspensions was extended beyond 2 s. The results add weight to recent claims that acetaldehyde toxicity is responsible for some of the effects previously ascribed to ethanol in alcohol fermentations, especially Zymomonas fermentations. Further work is required to confirm the importance of acetaldehyde toxicity under other culture conditions. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 71-78 
    ISSN: 0006-3592
    Keywords: Zymomonas ; yeast ; acetaldehyde ; ethanol ; stress ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The lag phase of Saccharomyces cerevisiae subjected to a step increase in temperature or ethanol concentration was reduced by as much as 60% when acetaldehyde was added to the medium at concentrations less than 0.1 g/L. Maximum specific growth rates were also substantially increased. Even greater proportional reductions in lag time due to acetaldehyde addition were observed for ethanol-shocked cultures of Zymomonas mobilis. Acetaldehyde had no effect on S. cerevisiae cultures started from stationary phase inocula in the absence of environmental shock and its lag-reducing effects were greater in complex medium than in a defined synthetic medium. Acetaldehyde reacted strongly with the ingredients of complex culture media. It is proposed that the effect of added acetaldehyde may be to compensate for the inability of cells to maintain transmembrane acetaldehyde gradients following an environmental shock. © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 15 (1993), S. 1199-1204 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Acetaldehyde at above about 0.3 g/l inhibited yeast growth, suggesting that it may contribute to product inhibition in alcohol fermentations when present at high concentrations intracellularly. The toxic effects of acetaldehyde and ethanol were not mutually reinforcing, acetaldehyde appearing to alleviate slightly the effects of ethanol. In support of this, low concentrations of acetaldehyde greatly reduced the lag phase in ethanol-containing medium and increased the specific growth rate.
    Type of Medium: Electronic Resource
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