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  • 1
    Electronic Resource
    Electronic Resource
    Feasibility of using water-immiscible organic solvents in biological waste-gas treatment (1995)
    Springer
    Bioprocess and biosystems engineering 12 (1995), S. 55-63 
    Details
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to conclude about the feasibility of using water-immiscible organic solvents in biological waste-gas treatment, a theoretical study was done in which different types of organic-solvent-containing systems are compared with systems where the pollutant is transferred directly to the water phase. For each system the total equipment volume needed to remove 99% of a pollutant from a waste-gas stream is calculated. Three different pollutants with a different solubility in water are considered: Hexane (m gw =71), dichloromethane (m gw =0.1) and acetone (m gw =0.0016), withm gw the partition coefficient (kg/m3 gas/kg/m3 water) of the pollutant between the gas and the water phase. From the results it is concluded that the use of organic solvents is only advantageous in case the specific area for mass transfer between solvent and water is large enough to compensate for the additional transport resistance introduced by the solvent, and secondly if the solvent shows a sufficiently high affinity for the pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01112994
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  • 2
    Electronic Resource
    Electronic Resource
    Specific rates of substrate oxidation and product formation in autotrophically growingChromatium vinosum cultures (1978)
    Springer
    Archives of microbiology 119 (1978), S. 135-143 
    Details
    ISSN: 1432-072X
    Keywords: Chromatium vinosum ; Storage polymers ; Electron donor oxidation ; Glycogen synthesis ; CO2 fixation ; Reducing power
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kinetics ofChromatium metabolism under autotrophic conditions were studied in batch culture. Description of various over-all metabolic rates in equal dimensions enabled direct comparison of such different processes as electron donor oxidation, storage-polymer synthesis, and growth. In the presence of sulfide, the specific rate of sulfur oxidation is partly depressed. Upon sulfide depletion, the latter rate showed an instantaneous increase of 22%. Simultaneously, glycogen was degraded. These two modifications fully compensate for the absence of sulfide, thus enabling growth to continue withμ max (0.12 h-1). These findings indicate that the potential rate of supply of electrons exceeds the biosynthetic demand for reducing power. The synthesis of glycogen in the presence of sulfide may be regarded overflow metabolism, assuming theμ max is intrinsically limited at 0.12 h-1. An alternative hypothesis is based on the assumption of an ineffective glycogen-synthesis regulation. Conceivably, growth and glycogen synthesis are competing for biosynthetic intermediates, the supply of which is limited by the maximum specific rate of e.g. the Calvin cycle. If so, both growth and glycogen synthesis are performed at submaximal rates. The rate of glycogen synthesis is greatly enhanced by the addition of growth inhibitors, and an increasedμ max value is found in the presence of acetate. These two findings together are consistent with the second hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00964264
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  • 3
    Electronic Resource
    Electronic Resource
    Coexistence of Chlorobium and Chromatium in a sulfide-limited continuous culture (1981)
    Springer
    Archives of microbiology 129 (1981), S. 32-34 
    Details
    ISSN: 1432-072X
    Keywords: Chromatium vinosum ; Chlorobium limicola ; Compention ; Coexistence ; Continuous culture ; Sulfide oxidation ; Sulfur oxidation ; Dual substrate limitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Competition experiments between Chromatium vinosum and Chlorobium limicola in sulfide-limited continuous culture under photolithoautotrophic conditions resulted in the coexistence of both organisms. The ratio between the two bacteria was dilution-rate as well as pH dependent. The observed coexistence can be explained as a hitherto not reported form of dual substrate limitation. The two substrates involved are the electron donors sulfide (growth-limiting substrate in the reservoir vessel) and extracellular elemental sulfur (formed by Chlorobium as a result of sulfide oxidation). It is argued that, although Chlorobium may have the better affinity for both substrates involved, Chromatium can compete successfully on the basis of its intracellular storage of sulfur. Ecological implication of the observed coexistence with respect to natural blooms are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417175
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  • 4
    Electronic Resource
    Electronic Resource
    Actual and potential rates of substrate oxidation and product formation in continuous cultures ofChromatium vinosum (1979)
    Springer
    Archives of microbiology 121 (1979), S. 161-167 
    Details
    ISSN: 1432-072X
    Keywords: Chromatium vinosum ; Sulfide oxidation ; sulfur turnover ; Glycogen turnover ; Reducing power storage ; Continuous culture ; Transient states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kinetics of electron-donor oxidation, storage-polymer formation and growth were studied in continuous cultures ofChromatium under conditions of balanced growth as well as during transient states. Under steady-state conditions, glycogen was accumulated at all dilution rates. This observation is consistent with previously postulated ideas about an ineffective glycogen-synthesis regulation. Upon perturbing the steady states, brought about by injection of extra sulfide into steady-state cultures, the following phenomena were observed immediately, irrespective of the dilution rate: the specific rate of sulfide oxidation increased to the value found in batch cultures, the sulfur-oxidation rate was decreased, the specific glycogen-synthesis rate increased, the increment being higher the lower the dilution rate, but an increase in the specific growth rate, if any, was below the limit of detection. The inverse relationship between the specific rates of glycogen synthesis and growth after removing the substrate limitation is to be explained by a shortage of intermediates, rather than by a growth-rate dependent intrinsic glycogen-synthesis limitation, because upon complete inhibition of growth a further increase in the rate of glycogen synthesis was observed. Essayed in this way, identical glycogen-synthesis rates were found at all dilution rates. Competitive advantages of such an apparently not adapted metabolism in environments with diurnal fluctuations in substrate concentrations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689981
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  • 5
    Electronic Resource
    Electronic Resource
    Feasibility of using water-immiscible organic solvents in biological waste-gas treatment (1995)
    Springer
    Bioprocess engineering 12 (1995), S. 55-63 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  In order to conclude about the feasibility of using water-immiscible organic solvents in biological waste-gas treatment, a theoretical study was done in which different types of organic-solvent-containing systems are compared with systems where the pollutant is transferred directly to the water phase. For each system the total equipment volume needed to remove 99% of a pollutant from a waste-gas stream is calculated. Three different pollutants with a different solubility in water are considered: Hexane (m gw =71), dichloromethane (m gw =0.1) and acetone (m gw =0.0016), with m gw the partition coefficient (kg/m3 gas/kg/m3 water) of the pollutant between the gas and the water phase. From the results it is concluded that the use of organic solvents is only advantageous in case the specific area for mass transfer between solvent and water is large enough to compensate for the additional transport resistance introduced by the solvent, and secondly if the solvent shows a sufficiently high affinity for the pollutants. List of symbols a specific area for mass transfer [m-1] a p packing material specific area [m-1] C pollutant concentration [kg . m-3] D pollutant diffusivity [m2 . s-1] d stirrer diameter [m] d p bubble, droplet or packing material diameter [m] g acceleration of the gravity [m . s-2] Gr Grashof number: g*d 3* p Δρ*(ρ/μ)2/ρ [dimensionless] H height [m] K overall mass-transfer coefficient [m . s-1] k partial mass-transfer coefficient [m . s-1] m gw partition coefficient of the pollutant in the system gas/water [kg/m3 gas/kg/m3 water] m gs partition coefficient of the pollutant in the system gas/solvent [kg/m3 gas /kg/m3 solvent] sw partition coefficient of the pollutant in the system solvent/water: m gw /m gs [kg/m3 solvent /kg/m3 water] P power input per unit mass of fluid [W . kg-1] Q flow [m3 . s-1] Re Reynolds number: ρ*ν*d p /μ [dimensionless] Sc Schmidt number: μ/ρ*D [dimensionless] Sh Sherwood number: k*d p /D [dimensionless] T tank diameter [m] t time [s] v bs bubble rising velocity [m . s-1] v s superficial velocity [m . s-1] V volume [m3] φ void fraction [dimensionless] ɛ hold-up [dimensionless] ρ density [kg . m-3] μ dynamic viscosity [kg . m-1s-1] δ film thickness [m] σ interfacial tension [kg . s-2] Δρ density difference [kg . m-3] τ residence time [s] Subscripts c coalescence layer in to the equipment out from the equipment g gas phase s solvent phase w water phase
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01112994
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of bacterial aggregates in a continuous-flow reactor: Influence of carrier availability (1988)
    Springer
    Biotechnology letters 10 (1988), S. 171-176 
    Details
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A dilution-rate shift-up was employed to induce bacterial hold-up in a continuous-flow gas-lift reactor. A minimum carrier concentration (sand, 2–5 g/l) was found a prerequisite for formation of bacterial aggregates, which fermented glucose either to propionate/acetate or to butyrate/acetate. Higher levels of sand did not affect the onset of propionate/acetate-forming aggregates, but decreased the rate at which they subsequently grew. Reversely, butyrate/acetate-producing aggregates grew at a constant rate but the onset of their formation was progressively retarded by increasing sand concentrations. In both cases, completion of start-up was most rapid at low sand concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01134821
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancement of the gas-to-water ethene transfer coefficient by a dispersed water-immiscible solvent: effect of the cells (1996)
    Springer
    Applied microbiology and biotechnology 46 (1996), S. 497-502 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract   For a mass-transfer-limited system, it was demonstrated that the volumetric ethene transfer coefficient (k l a) from gas to water could be enhanced by dispersing adequate amounts of a water-immiscible organic liquid, namely the perfluorocarbon FC40, in the aqueous phase. When 26% (v/v) FC40 was dispersed in a culture of Mycobacterium parafortuitum an enhancement of k l a, calculated on a total liquid volume basis, of 1.8 times was found. Steady-state experiments in the absence of microorganisms, however, showed a 1.2-fold enhancement of k l a at 18.5% (v/v) FC40. At all FC40 volume fractions tested, enhancement factors with cells were higher than enhancements without cells; apparently the microorganisms or their excretion products affected the interfacial areas or characteristic phase dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050850
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  • 8
    Electronic Resource
    Electronic Resource
    Acidogenic fermentation of protein/carbohydrate mixtures by bacterial populations adapted to one of the substrates in anaerobic chemostat cultures (1986)
    Springer
    Applied microbiology and biotechnology 23 (1986), S. 245-249 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The influence of the adaptation procedure on the simultaneous fermentation of glucose and gelatin by putatively carbon-limited mixed anaerobic bacterial populations was investigated. In one series of experiments glucose, dissolved in a mineral salts solution, was fed to mixed populations of bacteria in anaerobic carbon-limited chemostat cultures maintained at different pH values and at 30°C. When, after reaching a steady state, the carbon substrate was switched to gelatin, growth ceased. However, when gelatin was added to the medium as a second carbon substrate, it was found in all cases that hydrolysis and fermentation of the protein proceeded to a limited extent (〈30%) and that glucose continued to be completely metabolized. In a second series of experiments, bacterial populations were adapted to gelatin under comparable experimental conditions. After reaching a steady state, glucose was added to the medium as a second carbon substrate. Following establishment of the new steady state it was found that hydrolysis of gelatin was not inhibited but its fermentation was. It is concluded that anaerobic bacterial populations can loose their ability to degrade a protein substrate, depending on the adaptation procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261923
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  • 9
    Electronic Resource
    Electronic Resource
    Inhibition of the acidogenic dissimilation of glucose in anaerobic continuous cultures by free butyric acid (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 89-94 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In anaerobic wastewater treatment the separation of fermentative and methanogenic bacteria is aimed at an increased performance of the total digestion process. It is known that the attainable growth rate of the acidogenic population in continuous culture decreases at increasing influent concentrations of glucose. To account for this phenomenon, a new kinetic model was developed that combines substrate and product inhibition. In the present research product inhibition was investigated quantitatively in a continuous culture fermenting 50 mmol/l glucose. Extra acetate and butyrate were added up to 200 mmol/l at different pH values, and it turned out that only free butyric acid inhibited growth. The lower attainable growth rates of cultures producing comparable amounts of butyrate when fed with concentrated influents, strongly indicated substrate inhibition. Evidence is presented that transitions to low-conversion steady states predicted by the kinetic model, play a role and decrease the stability of the culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00258357
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  • 10
    Electronic Resource
    Electronic Resource
    New technique for kla measurement between gas and water in aerated solvent-in-water dispersions (1996)
    Springer
    Biotechnology techniques 10 (1996), S. 195-198 
    Details
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A new technique is presented to determine gas-to-water overall volumetric mass transfer coefficients (k l a) in a stirred-tank reactor containing solvent-in-water dispersions. The compound to be transferred from the gas to the water was toluene; the water-immiscible organic solvent was FC40, a perfluorocarbon. The k l a was determined in steady-state conditions in the absence of biological consumption. Toluene removal was achieved by passing a continuous flow of toluene-free water through the reactor. When solvent was present it was separated from the water at the reactor outlet by means of a small settler and recycled back to the vessel. The k l a was found to increase with the FC40 volume fraction. An enhancement of 1.9 times on an aqueous-phase-volume basis was found at 15 % (v/v) FC40.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00158945
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