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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 39 (2000), S. 145 -152 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Twenty-eight bacterial strains were isolated from an ecosystem adapted to fluctuating oxic–anoxic conditions. This ecosystem comprised a mixture of different natural and wastewater treatment environments. Among the 28 strains isolated, 10 exhibited aerobic denitrifying activity, i.e., co-respiration of oxygen and nitrate and simultaneous production of nitrite by 4 of them and of nitrogen gas by the remaining 6. Comparisons between the 16S rDNA sequences of the 10 strains showed that 3 of them were identical to M. aerodenitrificans, whereas RAPD profiles showed that the 3 strains were identical to each other but that they were different from M. aerodenitrificans. This implies that alternating aerobic–anoxic conditions allowed the isolation of a new strain of this aerobic denitrifier. Moreover, other denitrifying bacteria belonging to the genera Paracoccus, Thiobacillus, Enterobacter, Comamonas, and Sphingomonas were isolated in this way. These data imply that a wide variety of bacteria are able to carry out this type of metabolism. M. aerodenitrificans was also detected in methanogenic, denitrifying, nitrifying, phosphate removal, and activated sludge ecosystems by two-step PCR amplification. After 4 months of acclimation to oxic–anoxic phases, the strain was also detected in a canal and in a pond. This suggests that there is no specific natural ecological niche for aerobic denitrifiers but, as soon as selective pressure such as alternating aeration conditions is applied, this metabolism is amplified.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Temperature ; Growth ; Maintenance ; Candida lipolytica ; n-alcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of growth temperature on the evolution of kinetic parameters and yields was determined for Candida lipolytica cultures with ntetradecane as substrate, in a temperature range of 18°C to 30°C, which is below the critical growth temperature in order to work only in the activation zone of these parameters. In such a culture limited by substrate transfer, growth rate depends on biological rates, related to microorganisms characteristics, and diffusional rates, related to mass transfer. The effect of temperature thus depends on the limiting step. The activation energy, calculated from exponential growth rate determinations is $$E_{\mu _m } = 63,600{\text{ }}J/mole$$ . When the activation energy is calculated from the maximal rate of cell production (determined at the growth curve's inflexion point), it's found to be E μX=71,200 J/mole in the 18°C–24°C range, and E μX=28,000 J/mole in the 24°C–30°C range. The latter one is characteristic of a diffusion-limited process. Above 24°C, growth is controlled by substrate-transfer, as physiological potentialities are preferentially increased with temperature than diffusional ones: 24°C is thus the transition temperature T t from physiological to diffusional limitation. The apparent yield is almost constant, over the 18°C to 30°C temperature range, although maintenance coefficients are very dependent on temperature. The activation energies related to maintenance coefficients for alkane and oxygen respectively are $$E_{m_s } = 82,500{\text{ }}J/mole$$ and $$E_{mO_{\text{2}} } = 86,200{\text{ }}J/mole$$ . The m s/mO 2 ratio is about 3 (g/g), whereas that, for a strict oxidation reaction of n-tetradecane ought to be 3.47 (g/g). A satisfactory correlation, relating maintenance coefficients to the maximal growth rate of yeast, is given.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Fermentation Technology 66 (1988), S. 417-422 
    ISSN: 0385-6380
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0922-338X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 14 (1994), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A number of bacteria were isolated from different anoxic reactors. Those having denitrifying potential were tested for their ability to denitrify under aerobic conditions. The activity of their denitrifying enzymes varied from partial inactivation by oxygen (strains NO2B9 and TCET1) to oxygen-independent activity in a strain named SGLY2 which was tentatively identified as Comamonas sp. The effect of different aeration conditions on growth and on denitrification of SGLY2 was studied more extensively. This strain was able to consume oxygen and nitrate simultaneously with the production of nitrogen and without build-up of nitrite. The dissimilatory nitrate-reductase of nitrate-adapted cells was found to be more active in the presence of oxygen than in micro-aerobic or strictly anaerobic conditions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 10 (1994), S. 115-122 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Qualitative Reasoning is a set of Artificial Intelligence theories, methods, and techniques that provide an answer to modeling problems in domains in which one can have a clear notion of how a system is functioning without being able to express it as classical mathematical equations, and where is posed the problem of using jointly quantitative and qualitative data, as well as processing a big amount of complex knowledge. SIMAO (‘a System to Interpret Measurements And Observations’) is an attempt to deal with such problems. Although primarily devised for heterogeneous data interpretation in hydroecology, it was thought possible to use SIMAO in a wider context, like biotechnological processes. Starting from specific problems posed by a batch fermentation, the D-xylose conversion into ethanol by the yeast Pichia stipitis, this paper describes how was built and used a SIMAO model aimed at predicting the fermentation issue from initial conditions, i.e. set-points values and substrate concentration.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 15 (1996), S. 317-322 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A simple method for dissolved sulfide determination in colored complex media was developed using ion exchange chromatography. Its principle is based on the complete oxidation of an unstable compound (sulfide) into its stable form (sulfate) through a strong oxidant: hydrogen peroxide. The difference between sample analyzed before and after this treatment gives the total dissolved sulfide. In order to avoid H2S exhaust, this oxidation has to be performed immediately after sampling, without cell separation. In that way, standard solutions were prepared using raw anaerobic effluents from an industrial plant. It was shown in the calibration curve that no bacterial interaction was present. Finally, sulfide from continuous and discontinuous digestions of these sulfate rich wastewaters were successfully assayed by this technique. A theoretical evaluation based on Henry's law and the sulfide dissociation equilibrium led to a very good agreement with the analytical results.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 46 (1996), S. 92-97 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Denitrification of a high-strength synthetic wastewater (150 g NO- 3 l-1) was carried out using a wine distillery effluent as an example of an industrial carbon source (22.7 g chemical oxygen demand l-1). Two configurations were tested: one consisted of an acidogenesis reactor followed by a denitrifying reactor and the other was a single reactor directly fed with the raw effluents. In both cases, denitrification was achieved at a nitrate load of 9.54 g NO- 3 l-1 day-1 (2.19 g N as NO- 3 l-1 day-1) with good specific reduction rates: 32.6 mg and 35.2 mg N as NO x  g volatile suspended solids h-1, calculated on a single day, for the two-step and the one-step process respectively. Dissimilatory nitrate reduction to ammonium did not occur, even in the one-step process.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 155-161 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of substrate concentration (S 0) on the fermentation parameters of a sugar mixture byPichia stipitis Y 7124 was investigated under anaerobic and microaerobic conditions. Under microaerobiosisP. stipitis maintained high ethanol yield and productivity when initial substrate concentration did not exceed 150 g/l; ethanol yield of about 0.40 g/g and volumetric productivity up to 0.39 g/l per hour were obtained. Optimal specific ethanol productivity (0.2 g/g per hour) was observed withS 0=110 g/l. Under anaerobic conditionsP. stipitis exhibited the highest fermentative performances atS 0=20 g/l; it produced ethanol with a yield of 0.42 g/g, with a specific rate of 1.1 g/g per day. When the initial substrate level increased, specific ethanol productivity declined gradually and ethanol yield was dependent on the degree of utilization of each sugar in the mixture.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 155-161 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of substrate concentration (S 0) on the fermentation parameters of a sugar mixture byPichia stipitis Y 7124 was investigated under anaerobic and microaerobic conditions. Under microaerobiosisP. stipitis maintained high ethanol yield and productivity when initial substrate concentration did not exceed 150 g/l; ethanol yield of about 0.40 g/g and volumetric productivity up to 0.39 g/l per hour were obtained. Optimal specific ethanol productivity (0.2 g/g per hour) was observed withS 0=110 g/l. Under anaerobic conditionsP. stipitis exhibited the highest fermentative performances atS 0=20 g/l; it produced ethanol with a yield of 0.42 g/g, with a specific rate of 1.1 g/g per day. When the initial substrate level increased, specific ethanol productivity declined gradually and ethanol yield was dependent on the degree of utilization of each sugar in the mixture.
    Type of Medium: Electronic Resource
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