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  • 1
    Electronic Resource
    Electronic Resource
    Influence of biomass accumulation on bed expansion characteristics of a down-flow anaerobic fluidized-bed reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 136-144 
    Details
    ISSN: 0006-3592
    Keywords: down-flow fluidization ; bed expansion ; biofilm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes the bed expansion characteristics of a down-flow anaerobic fluidized bed reactor treating a synthetic wastewater. Experiments were carried out in a 0.08 m diameter and 1 m length PVC column. The carrier used was ground perlite (an expanded volcanic rock). Particles characteristics were 0.968 mm in diameter, specific density of 213 kg · m-3 and Umf (minimal fluidization velocity): 2.3 m · h-1. Experimental data of terminal velocities and bed expansion parameters at several biofilm thicknesses were compared to different models predicting the bed expansion of up-flow and down-flow fluidized beds.Measured bed porosities at different liquid superficial velocities for the different biofilm thicknesses were in agreement with the Richardson-Zaki model, when Ut (particle terminal velocity) and n (expansion coefficient) were calculated by linear regression of the experimental data. Terminal velocities of particles at different biofilm thicknesses calculated from experimental bed expansion data, were found to be much smaller than those obtained when Cd (drag coefficient) is determined from the standard drag curve (Lapple and Sheperd, 1940) or with others' correlations (Karamanev and Nikolov, 1992a,b). This difference could be explained by the fact that free-rising particles do not obey Newton's law for free-settling, as proposed by Karamanev and Nikolov (1992a,b) and Karamanev et al. (1996). In the present study, the same free-rising behavior was observed for all particles (densities between 213 and 490 kg · m-3). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 136-144, 1998.
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 627-635 
    Details
    ISSN: 0006-3592
    Keywords: airlift reactor ; biofilm ; hydrodynamics ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 627-635, 1998.
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  • 3
    Electronic Resource
    Electronic Resource
    Mathematical modeling of biofilm structure with a hybrid differential-discrete cellular automaton approach (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 101-116 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; structure ; shape ; surface ; cellular automata ; discrete ; modeling ; roughness ; fractal ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A hybrid differential-discrete mathematical model has been used to simulate biofilm structures (surface shape, roughness, porosity) as a result of microbial growth in different environmental conditions. In this study, quantitative two- and three-dimensional models were evaluated by introducing statistical measures to characterize the complete biofilm structure, both the surface structure and volume structure. The surface enlargement, coefficient of roughness, fractal dimension of surface, biofilm compactness, and solids hold-up were found to be good measures of biofilm structure complexity. Among many possible factors affecting the biofilm structure, the influence of biomass growth in relation to the diffusive substrate transport was investigated. Porous biofilms, with many channels and voids between the “finger-like” or “mushroom” outgrowth, were obtained in a substrate-transport-limited regime. Conversely, compact and dense biofilms occurred in systems limited by the biomass growth rate and not by the substrate transfer rate. The surface complexity measures (enlargement, roughness, fractal dimension) all increased with increased transport limitation, whereas the volume measures (compactness, solid hold-up) decreased, showing the change from a compact and dense to a highly porous and open biofilm. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:101-116, 1998.
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  • 4
    Electronic Resource
    Electronic Resource
    Mobilization of broad host range plasmid from Pseudomonas putida to established biofilm of Bacillus azotoformans. II. Modeling (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 280-286 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; plasmid transfer ; conjugation ; mathematical models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A strain of Pseudomonas putida that harbors plasmids RK2 and pDLB101 was exposed to a pure culture biofilm of Bacillus azotoformans grown in a rotating annular reactor. Transfer of the RK2 mobilizable pDLB101 plasmid to B. azotoformans was monitored over a 4-day period. Experimental results demonstrated that the broad host range, RSF1010 derivative pDLB101 was transferred to and expressed by B. azotoformans. In the companion article to this work, the rate of plasmid transfer was quantified as a function of the limiting nutrient, succinate, and as a function of the mechanism of transfer. A biofilm process simulation program (AQUASIM) was modified to analyze resultant experimental data. Although the AQUASIM package was not designed to simulate or predict genetic events in biofilms, modification of the rate process dynamics allowed successful modeling of plasmid transfer. For the narrow range of substrate concentrations used in these experiments, nutrient level had only a slight effect on the rate and extent of plasmid transfer in biofilms. However, further simulations using AQUASIM revealed that under nutrient poor conditions, the number of transconjugants appearing in the biofilm was limited. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 280-286, 1998.
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  • 5
    Electronic Resource
    Electronic Resource
    Activity and stability of a recombinant plasmid-borne TCE degradative pathway in biofilm cultures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 318-327 
    Details
    ISSN: 0006-3592
    Keywords: plasmid ; retention ; TCE ; biofilm ; segregational stability ; activity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The activity and stability of the TCE degradative plasmid TOM31c in the transconjugant host Burkholderia cepacia 17616 was studied in selective and non-selective biofilm cultures. The activity of plasmid TOM31c in biofilm cultures was measured by both TCE degradative studies and the expression of the Tom pathway. Plasmid loss was measured using continuous flow, rotating annular biofilm reactors, and various analytical and microbiological techniques. The probability of plasmid loss in the biofilm cultures was determined using a non-steady-state biofilm plasmid loss model that was derived from a simple mass balance, incorporating results from biofilm growth and plasmid loss studies. The plasmid loss model also utilized Andrew's inhibition growth kinetics and a biofilm detachment term.Results from these biofilm studies were compared to similar studies performed on suspended cultures of Burkholderia cepacia 17616-TOM31c to determine if biofilm growth has a significant effect on either plasmid retention or Tom pathway expression (i.e., TCE degradation rates). Results show that the activity and expression of the Tom pathway measured in biofilm cultures was significantly less than that found in suspended cultures at comparable growth rates. The data obtained from these studies fit the plasmid loss model well, providing plasmid loss probability factors for biofilm cultures that were equivalent to those previously found for suspended cultures. The probability of plasmid loss in the B. cepacia 17616-TOM31c biofilm cultures was equivalent to those found in the suspended cultures. The results indicate that biofilm growth neither helps nor hinders plasmid stability. In both the suspended and the biofilm cultures, plasmid retention and expression could be maintained using selective growth substrates and/or an appropriate plasmid-selective antibiotic. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:318-327, 1998.
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  • 6
    Electronic Resource
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    Mobilization of broad host range plasmid from Pseudomonas putida to established biofilm of Bacillus azotoformans. I. Experiments (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 272-279 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; plasmid transfer ; conjugation ; retrotransfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A strain of Pseudomonas putida harboring plasmids RK2 and pDLB101 was exposed to a pure culture biofilm of Bacillus azotoformans grown in a rotating annular reactor under three different concentrations of the limiting nutrient, succinate. Experimental results demonstrated that the broad host range RSF1010 derivative pDLB101 was transferred to and expressed by B. azotoformans. At the lower concentrations, donor mediated plasmid transfer increased with increasing nutrient levels, but the highest nutrient concentration yielded the lowest rate of donor to recipient plasmid transfer. For transconjugant initiated transfer, the rate of transfer increased with increasing nutrient concentrations for all cases. At the lower nutrient concentrations, the frequency of plasmid transfer was higher between donors and recipients than between transconjugants and recipients. The reverse was true at the highest succinate concentration. The rates and frequencies of plasmid transfer by mobilization were compared to gene exchange by retrotransfer. The initial rate of retrotransfer was slower than mobilization, but then increased dramatically. Retrotransfer produced a plasmid transfer frequency more than an order of magnitude higher than simple mobilization. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 272-279, 1998.
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  • 7
    Electronic Resource
    Electronic Resource
    A new combined differential-discrete cellular automaton approach for biofilm modeling: Application for growth in gel beads (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 718-731 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; modeling ; reaction-diffusion-growth ; cellular automata ; immobilized cells ; structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The theoretical basis and quantitative evaluation of a new approach for modeling biofilm growth are presented here. Soluble components (e.g., substrates) are represented in a continuous field, whereas discrete mapping is used for solid components (e.g., biomass). The spatial distribution of substrate is calculated by applying relaxation methods to the reaction-diffusion mass balance. A biomass density map is determined from direct integration in each grid cell of a substrate-limited growth equation. Spreading and distribution of biomass is modeled by a discrete cellular automaton algorithm. The ability of this model to represent diffusion-reaction-microbial growth systems was tested for a well-characterized system: immobilized cells growing in spherical gel beads. Good quantitative agreement with data for global oxygen consumption rate was found. The calculated concentration profiles of substrate and biomass in gel beads corresponded to those measured. Moreover, it was possible, using the discrete spreading algorithm, to predict the spatial two- and three-dimensional distribution of microorganisms in relation to, for example, substrate flux and inoculation density. The new technique looks promising for modeling diffusion-reaction-microbial growth processes in heterogeneous systems as they occur in biofilms. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 718-731, 1998
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  • 8
    Electronic Resource
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    Influence of biomass production and detachment forces on biofilm structures in a biofilm airlift suspension reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 400-407 
    Details
    ISSN: 0006-3592
    Keywords: abrasion ; airlift reactor ; biofilm ; structure ; density ; surface shape ; thickness ; shear ; carrier concentration ; substrate loading ; detachment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Suspension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and microbial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/m3 · day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were performed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detachment forces. The higher biomass content is associated with a lower biomass substrate loading rate and therefore with a lower biomass yield (from 0.4 down to 0.12 gbiomass/gacetate). Contrary to general beliefs, the observed biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuberances), denser and thinner compact biofilms were obtained when the biomass surface production rate decreased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance between biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low detachment forces, the biofilm becomes highly heterogeneous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:400-407, 1998.
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  • 9
    Electronic Resource
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    Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 536-544 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; streamers ; biofouling ; drag ; fast Fourier transform analysis ; hydrodynamics ; oscillations ; pressure drop ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 μm in diameter. The largest clusters were approximately 85 μm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 536-544, 1998.
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  • 10
    Electronic Resource
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    A proposed transient model for cometabolism in biofilm systems (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 541-550 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; dual substrate limitation ; cometabolism ; secondary substrate ; biofilm modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model was developed to describe the behaviour of primary and secondary substrates in a biofilm reactor. The model incorporates structured kinetics to describe the generation and consumption of reducing power in the catabolic and respiratory subsystems, respectively. Secondary substrate transformation through oxygenolytic or reductive mechanisms can be modelled under either single or dual limitation of the electron donor and electron acceptor substrates. An example simulation of a theoretical biofilm system was performed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 541-550, 1998.
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  • 11
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    Respirometric assay for biofilm kinetics estimation: Parameter identifiability and retrievability (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 35-45 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; attached growth ; respirometry ; parameter estimation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Currently, no fast and accurate methods exist for measuring extant biokinetic parameters for biofilm systems. This article presents a new approach to measure extant biokinetic parameters of biofilms and examines the numerical feasibility of such a method. A completely mixed attached growth bioreactor is subjected to a pulse of substrate, and oxygen consumption is monitored by on-line measurement of dissolved oxygen concentration in the bulk liquid. The oxygen concentration profile is then fit with a mechanistic mathematical model for the biofilm to estimate biokinetic parameters. In this study a transient biofilm model is developed and solved to generate dissolved oxygen profiles in the bulk liquid. Sensitivity analysis of the model reveals that the dissolved oxygen profiles are sufficiently sensitive to the biokinetic parameters - the maximum specific growth rate coefficient (⁁μ) and the half-saturation coefficient (Ks) - to support parameter estimation if accurate estimates of other model parameters can be obtained. Monte Carlo simulations are conducted with the model to add typical measurement error to the generated dissolved oxygen profiles. Even with measurement error in the dissolved oxygen profile, a pair of biokinetic parameters is always retrievable. The geometric mean of the parameter estimates from the Monte Carlo simulations prove to be an accurate estimator for the true biokinetic values. Higher precision is obtained for ⁁μ estimates than for Ks estimates. In summary, this theoretical analysis reveals that an on-line respirometric assay holds promise for measuring extant biofilm kinetic parameters. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 35-45, 1998.
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  • 12
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    Soil immobilization: New concept for biotreatment of soil contaminants (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 471-476 
    Details
    ISSN: 0006-3592
    Keywords: soil immobilization ; soil pollutants ; bioremediation ; bioreactor ; biofilm ; pentachlorophenol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new concept for the development of microbial consortia for the degradation of persistent soil pollutants and for pollutant treatment is proposed. The concept defined as “soil immobilization” is based on the entrapment of soil particles, showing microbial activity in degrading the target pollutant, into a solid membrane with a large pore size distribution. The particular hydrodynamic and mass transfer properties of this system result in a very efficient process. A new type of bioreactor is proposed for carrying out the immobilized soil process. The performance of the system was tested by developing a microbial system for the mineralization of pentachlorophenol (PCP). The results show that the volumetric efficiency of the process for PCP mineralization in the immobilized soil bioreactor is 1-3 orders of magnitude higher than reported literature values. Chlorine and carbon atoms of PCP are both nearly completely (99%) mineralized. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 471-476, 1998.
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  • 13
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    Continuous biological waste gas treatment in stirred trickle-bed reactor with discontinuous removal of biomass (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 497-503 
    Details
    ISSN: 0006-3592
    Keywords: waste gas treatment ; trickle-bed reactor ; toluene ; biomass removal ; biofilm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new reactor for biological waste gas treatment was developed to eliminate continuous solvents from waste gases. A trickle-bed reactor was chosen with discontinuous movement of the packed bed and intermittent percolation. The reactor was operated with toluene as the solvent and an optimum average biomass concentration of between 5 and 30 kg dry cell weight per cubic meter packed bed (m3pb). This biomass concentration resulted in a high volumetric degradation rate. Reduction of surplus biomass by stirring and trickling caused a prolonged service life and prevented clogging of the trickle bed and a pressure drop increase. The pressure drop after biomass reduction was almost identical to the theoretical pressure drop as calculated for the irregular packed bed without biomass. The reduction in biomass and intermittent percolation of mineral medium resulted in high volumetric degradation rates of about 100 g of toluene m-3pb h-1 at a load of 150 g of toluene m-3pb h-1. Such a removal rate with a trickle-bed reactor was not reported before. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 497-503, 1998.
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  • 14
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    A review of experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 261-272 
    Details
    ISSN: 0006-3592
    Keywords: effective diffusive permeability ; diffusion coefficient ; biofilm ; cell density ; review ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms are reviewed. Effective diffusive permeabilities, the parameter appropriate to the analysis of reaction-diffusion interactions, depend on solute type and biofilm density. Three categories of solute physical chemistry with distinct diffusive properties were distinguished by the present analysis. In order of descending mean relative effective diffusive permeability (De/Daq) these were inorganic anions or cations (0.56), nonpolar solutes with molecular weights of 44 or less (0.43), and organic solutes of molecular weight greater than 44 (0.29). Effective diffusive permeabilities decrease sharply with increasing biomass volume fraction suggesting a serial resistance model of diffusion in biofilms as proposed by Hinson and Kocher (1996). A conceptual model of biofilm structure is proposed in which each cell is surrounded by a restricted permeability envelope. Effective diffusion coefficients, which are appropriate to the analysis of transient penetration of nonreactive solutes, are generally similar to effective diffusive permeabilities in biofilms of similar composition. In three studies that examine diffusion of very large molecular weight solutes ( 〉 5000) in biofilms, the average ratio of the relative effective diffusion coefficient of the large solute to the relative effective diffusion coefficient of either sucrose or fluorescein was 0.64, 0.61, and 0.36. It is proposed that large solutes are effectively excluded from microbial cells, that small solutes partition into and diffuse within cells, and that ionic solutes are excluded from cells but exhibit increased diffusive permeability (but decreased effective diffusion coefficients) due to sorption to the biofilm matrix. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:261-272, 1998.
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  • 15
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    Local macromolecule diffusion coefficients in structurally non-uniform bacterial biofilms using fluorescence recovery after photobleaching (FRAP) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 462-473 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; macromolecule transport mechanism ; local diffusion coefficients ; fluorescence recovery ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pure culture Pseudomonas putida biofilms were cultivated under controlled conditions to a desired overall biofilm thickness, then employed within classical half-cell diffusion chambers to estimate, from transient solute concentrations, the effective diffusion coefficient for several macromolecules of increasing molecular weight and molecular complexity. Results of traditional half-cell studies were found to be erroneous due to the existence of microscopic water channels or crevasses that perforate the polysaccharidic gel matrix of the biofilm, sometimes completely to the supporting substratum. Thus, half-cell devices measure a composite transfer coefficient that may overestimate the true, local flux of solutes in the biofilm polysaccharide gel matrix.An alternative analytical technique was refined to determine the local diffusion coefficients on a micro-scale to avoid the errors created by the biofilm architectural irregularities. This technique is based upon the Fluorescence Return After Photobleaching (FRAP), which allows image analysis observation of the transport of fluorescently labeled macromolecules as they migrate into a micro-scale photobleached zone. The technique can be computerized and allows one to map the local diffusion coefficients of various solute molecules at different horizontal planes and depths in a biofilm. These mappings also indirectly indicate the distribution of water channels in the biofilm, which was corroborated independently by direct microscopic observation of the settling of fluorescently-labeled latex spheres within the biofilm. Fluorescence return after photobleaching results indicate a significant reduction in the solute transport coefficients in biofilm polymer gel vs. the same value in water, with the reduction being dependent on solute molecule size and shape. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 462-473, 1998.
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  • 16
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    Influence of dissolved oxygen concentration on nitrite accumulation in a biofilm airlift suspension reactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 168-178 
    Details
    ISSN: 0006-3592
    Keywords: airlift reactor ; BAS reactor ; biofilm ; nitrification ; nitrite ; oxygen transfer ; residence time ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The biofilm airlift suspension (BAS) reactor can treat wastewater at a high volumetric loading rate combined with a low sludge loading. Two BAS reactors were operated, with an ammonium load of 5 kg N/(m3 d), in order to study the influence of biomass and oxygen concentration on the nitrification process. After start-up the nitrifying biomass in the reactors gradually increased up to 30 g VSS/L. Due to this increased biomass concentration the gas-liquid mass transfer coefficient was negatively influenced. The resulting gradual decrease in dissolved oxygen concentration (over a 2-month period) was associated with a concomitantly nitrite build-up. Short term experiments showed a similar relation between dissolved oxygen concentration (DO) and nitrite accumulation. It was possible to obtain full ammonium conversion with approximately 50% nitrate and 50% nitrite in the effluent. The facts that (i) nitrite build up occurred only when DO dropped, (ii) the nitrite formation was stable over long periods, and (iii) fully depending on DO levels in short term experiments, led to the conclusion that it was not affected by microbial adaptations but associated with intrinsic characteristics of the microbial growth system. A simple biofilm model based on the often reported difference of oxygen affinity between ammonium and nitrite oxydizers was capable of adequately describing the phenomena.Measurements of biomass density and concentration are critical for the interpretation of the results, but highly sensitive to sampling procedures. Therefore we have developed an independent method, based on the residence time of Dextran Blue, to check the experimental methods. There was a good agreement between procedures.The relation between biomass concentration, oxygen mass transfer rate and nitrification in a BAS reactor is discussed. © 1997 John Wiley & Sons, Inc.
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  • 17
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    Evidence of bacterial adaptation to monochloramine in Pseudomonas aeruginosa biofilms and evaluation of biocide action model (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 201-209 
    Details
    ISSN: 0006-3592
    Keywords: adaptation ; biofilm ; biocide ; disinfection ; model ; monochloramine ; Pseudomonas ; stress response ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model of biocide action against microbial biofilm was tested experimentally by measuring the response of Pseudomonas aeruginosa biofilm to various doses of monochloramine. Pure culture biofilm was developed in continuous flow annular reactors for 7 days, then treated with a 2-, 4-, or 8-h dose of 2 or 4 mg L-1 monochloramine. Some experiments investigated repeated treatment. Disinfection and regrowth of the biofilm were observed by sampling the biofilm for viable and total cell areal densities for up to 100 h following the biocide treatment. A phenomenological mathematical model was fitted to experimental data sets and captured overall trends, but it could not simulate certain experimentally observed features. The model did simulate rapid disinfection followed by steady regrowth. It correctly predicted a much greater decrease in viable than in total cell densities and also correctly captured the shapes of these trajectories. Discrepancies between the model and data included the following: the model predicted faster regrowth than was experimentally observed, the model predicted that a second dose would be more effective than the first dose but the opposite was observed in the experiments, and parameters estimated by fitting one dose concentration could not be used to predict the results of a different dose concentration or a second dose. Discrepancies between model and the experiment were hypothesized to be due to an adaptive stress response by the bacteria, a process not included in the model. A practical implication of this work is that it is more effective to deliver monochloramine in a short concentrated dose as opposed to a longer dose of lower concentration. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 201-209, 1997.
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    Relationship between mass transfer coefficient and liquid flow velocity in heterogenous biofilms using microelectrodes and confocal microscopy (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 681-688 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; confocal scanning laser microscopy ; laminar flow ; liquid flow velocity ; mass transfer coefficient ; microelectrodes ; Reynolds number ; Sherwood number ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The relationship between local mass transfer coefficient and fluid velocity in heterogenous biofilms was investigated by combining microelectrodes and confocal scanning laser microscopy (CSLM). The biofilms were grown for up to 7 days and consisted of cell clusters separated by interstitial channels. Mass transfer coefficient depth profiles were measured at specific locations in the cell clusters and channels at average flow velocities of 2.3 and 4.0 cm/s. Liquid flow velocity profiles were measured in the same locations using a particle tracking technique. The velocity profiles showed that flow in the open channel was laminar. There was no flow at the top surface of the biofilm cell clusters but the mass transfer coefficient was 0.01 cm/s. At the same depth in a biofilm channel, the flow velocity was 0.3 cm/s and the mass transfer coefficient was 0.017 cm/s. The mass transfer coefficient profiles in the channels were not influenced by the surrounding cell clusters. Local flow velocities were correlated with local mass transfer coefficients using a semi-theoretical mass transfer equation. The relationship between the Sherwood number (Sh,) the Reynolds number (Re,) and the Schmidt number (Sc) was found using the experimental data to find the dimensionless empirical constants (n1, n2, and m) in the equation Sh = n1 + n2Rem Sc1/3. The values of the constants ranged from 1.45 to 2.0 for n1, 0.22 to 0.28 for n2, and 0.21 to 0.60 for m. These values were similar to literature values for mass transfer in porous media. The Sherwood number for the entire flow cell was 10 when the bulk flow velocity was 2.3 cm/s and 11 when the bulk flow velocity was 4.0 cm/s. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 681-688, 1997.
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    Identification of linearity in the biofilm process and its operational utility (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 253-258 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; deep biofilm reactor (DBFR) ; kinetics ; linearity ; operational control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various reported field studies on the performance of biofilm reactors suggest that the linear control of the system is effective for maintaining the consistent treatment efficiency under changing environmental conditions. However, no theoretical basis is available in the literature to substantiate such a claim. In this article, inherent linearity of the biofilm process has been identified along with the conditions under which this linearity exists. Exploiting the linear state of the system, operational criteria for regulating the performance of the biofilm reactors are obtained. The utility and applicability of the developed criteria are numerically demonstrated. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 253-258, 1997.
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    Performance of a styrene-degrading biofilter containing the yeast Exophiala jeanselmei (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 259-266 
    Details
    ISSN: 0006-3592
    Keywords: waste gas ; styrene ; fungi ; biofilter performance ; biofilm ; Exophiala jeanselmei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general mathematical model developed for a description of pollutant degradation in a biofilm was used to evaluate the performance of a biofilter for the purification of styrene-containing gas. The biofilter contained perlite as an inert support on which a biofilm was present composed of a mixed microbial population containing the fungus Exophiala jeanselmei as a major styrene-degrading microorganism. Although styrene is a moderately hydrophobic compound, the biofilter was reaction limited at a styrene gas phase concentration of 0.1-2.4 g/m3. Limitation of biofilter performance by the mass transfer of styrene was only observed at styrene concentrations lower than 0.06 g/m3. A maximal styrene degradation rate of 62 g/(m3 · h) was maintaind for over 1 year. At a high styrene concentration, the maximal styrene degradation rate could be increased to 91 g/(m3 · h) by increasing the oxygen concentration in the gas from 20 to 40%. After 300 days of operation, the dry-weight biomass concentration of the filter bed was 41% (w/w), and an average biofilm thickness of 240-280 μm, but maximal up to 600 μm, was observed. Experimental results and model calculations indicated an effective biofilm thickness of about 80 μm. It is postulated that the thickness of the effective biofilm is determined by the oxygen availability in the biofilm. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 259-266, 1997.
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    Substrate utilization and mass transfer in an autotrophic biofilm system: Experimental results and numerical simulation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 363-371 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; autotrophic bacteria ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An autotrophic biofilm has been investigated for over 10 months in a biofilm tube reactor. The objective of this investigation was the verification and improvement of a biofilm model. The use of a Clark-type oxygen microelectrode in situ allowed the determination of the substrate flux in the biofilm. Also, the population dynamics of the autotrophic bacteria could be evaluated by varying the substrate conditions. Simulation of the experimental results showed that the liquid phase of the biofilm decreased with biofilm depth. This could be described by a logistic function. The density of the inert volume fraction was found to be higher than that of the viable bacteria. This was verified in a nonsubstrate phase of 5 weeks. Growth and decay of the autotrophic bacteria could be described by the growth, endogenous respiration, and death processes. Mass transfer coefficients at the bulk/biofilm interface were evaluated. They were found to be one order of magnitude higher than those known from hydrodynamics in tubes without a biofilm. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 363-371, 1997.
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    Control of heterotrophic layer formation on nitrifying biofilms in a biofilm airlift suspension reactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 397-405 
    Details
    ISSN: 0006-3592
    Keywords: airlift reactor ; biofilm ; biofilm detachment ; control biofilm formation ; heterotrophic layer ; hydraulic retention time ; nitrification ; oxygen diffusion limitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Biofilm Airlift Suspension (BAS) reactor was operated with nitrifying biofilm growth and heterotrophic suspended growth, simultaneously converting ammonium and acetate. Growth of heterotrophs in suspension decreases the diffusion limitation for the nitrifiers, and enlarges the nitrifying capacity of a biofilm reactor. Neither nitrifiers nor heterotrophs suffer from additional oxygen diffusion limitation when the heterotrophs grow in suspension. Control of the location of heterotrophic growth, either in suspension or in biofilms over the nitrifying biofilms, was possible by manipulation of the hydraulic retention time. A time delay for formation and disappearance of the heterotrophic biofilms of 10 to 15 days was observed. Surprisingly, it was found that in the presence of the heterotrophic layers the maximum specific activity on ammonia of the nitrifying biofilms increased. The reason for the increase in activity is unknown. The effect of heterotrophic biofilm formation on oxygen diffusion limitation for the nitrifiers is discussed. Some phenomena compensating the increased mass transfer resistance due to the growth of a heterotrophic layer are also presented. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 397-405, 1997.
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    Thermophilic sulphate and sulphite reduction in lab-scale gas-lift reactors using H2 and CO2 as energy and carbon source (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 807-814 
    Details
    ISSN: 0006-3592
    Keywords: sulphate reduction ; sulphite reduction ; biofilm ; immobilization ; gas-lift reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Feasibility of thermophilic (55°C) sulphate and sulphite reduction with H2 and CO2 gas-mixtures was studied in gas-lift reactors, which contained pumice particles as carrier material. Particular attention was paid to biomass retention and the competition between hydrogenotrophic sulphate-reducers and other hydrogenotrophic thermophiles. A model medium with defined mineral nutrients was used.The results of the experiments clearly demonstrate that sulphate conversion rates up to 7.5 g SO42-/L per day can be achieved. With sulphite, a reduction rate of 3.7 g S/L per day was obtained, which equals a sulphate conversion rate of 11.1 g SO42-/L per day. Under the applied conditions, a strong competition for hydrogen between hydrogenotrophic sulphate-reducers, tentatively designated as Desulfotomaculum sp., and hydrogenotrophic methanogens was observed. The outcome of the competition could not be predicted. Growth of the mixed culture was totally inhibited at an H2S concentration of 250 mg/L. Poor attachment of sulphate-reducing bacteria was observed in all experiments. The biomass concentration did not exceed 1.2 g/L, despite the presence of 50 g/L of pumice. The reason for this phenomenon remains to be understood. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 807-814, 1997.
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    Performance of a sulfide-oxidizing expanded-bed reactor supplied with dissolved oxygen (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 32-40 
    Details
    ISSN: 0006-3592
    Keywords: expanded-bed reactor ; sulfur ; Thiobacilli ; immobilization ; biofilm ; sludge ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of a new sulfide-oxidizing, expanded-bed bioreactor is described. To stimulate the formation of well-settleable sulfur sludge, which comprises active sulfide-oxidizing bacterial biomass and elemental sulfur, the aeration of the liquid phase and the oxidation of sulfide to elemental sulfur are spatially separated. The liquid phase is aerated in a vessel and subsequently recirculated to the sulfide-oxidizing bioreactor. In this manner, turbulencies due to aeration of the liquid phase in the bioreactor are avoided. It appeared that, under autotrophic conditions, almost all biomass present in the reactor will be immobilized within the sulfur sludge which consists mainly of elemental sulfur (92%) and biomass (2.5%). The particles formed have a diameter of up to 3 mm and can easily be grinded down. Within time, the sulfur sludge obtained excellent settling properties; e.g., after 50 days of operation, 90% of the sludge settles down at a velocity above 25 m h-1 while 10% of the sludge had a sedimentation velocity higher than 108 m h-1. Because the biomass is retained in the reactor, higher sulfide loading rates may be applied than to a conventional “free-cell” suspension. The maximum sulfide-loading rate reached was 14 g HS- L-1 d-1, whereas for a free-cell suspension a maximum loading rate of 6 g HS- L-1 d-1 was found. At higher loading rates, the upward velocities of the aerated suspension became too high so that sulfur sludge accumulated in the settling zone on top of the reactor. When the influent was supplemented with volatile fatty acids, heterotrophic sulfur and sulfate reducing bacteria, and possibly also (facultatively) heterotrophic Thiobacilli, accumulated within the sludge. This led to a serious deterioration of the system; i.e., the sulfur formed was increasingly reduced to sulfide, and also the formation rate of sulfur sludge declined. © 1997 John Wiley & Sons, Inc.
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    Adhesion and biofilm development on suspended carriers in airlift reactors: Hydrodynamic conditions versus surface characteristics (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 880-889 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; airlift reactor ; adhesion ; detachment ; surface characteristics ; Pseudomonas putida ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adhesion and biofilm formation by Pseudomonas putida was studied using suspended carriers in laboratory airlift reactors. Standard, roughened, hydrophobic, and positively charged glass beads, sand, and basalt grains were used as carriers. The results clearly show that in airlift reactors hydrodynamic conditions and particle collisions control biofilm formation. In the reactors, on surfaces subjected to different shear levels, biofilm formation differed considerably. This could be described by a simple growth and detachment model. Increased surface roughness promoted biofilm accumulation on suspended carriers. The physicochemical surface characteristics of the carrier surface proved to be less important due to the turbulent conditions in the airlift reactors. Adhesion of P. putida to glass beads was poor, and results of an adhesion test under quiescent conditions were not predictive for adhesion and subsequent biofilm formation under reactor conditions. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55:880-889, 1997.
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    Prediction of average biofilm density and performance of a spherical bioparticle under substrate inhibition (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 319-329 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; density ; thickness ; fluidized bed ; substrate consumption ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, a model was proposed to predict the average performance and biofilm density of a spherical bioparticle under substrate inhibition in a fluidized bed system. The average biofilm density and substrate consumption rates were predicted for a definite biofilm thickness and limiting substrate concentrations. A diffusion and reaction model was developed over the bioparticle with biofilm-density dependent effective diffusion coefficients for maximum substrate consumption theory. This theory predicts the optimum density of a biofilm to yield a maximum substrate consumption rate within the biofilm, developed for the first time with this study and experimentally verified. A good correlation was observed between the model prediction and experimental results for biofilm density and substrate consumption rates. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 319-329, 1997.
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    Simulation of citric acid production by rotating disk contactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 689-696 
    Details
    ISSN: 0006-3592
    Keywords: citric acid ; Aspergillus niger ; rotating disk contactor ; simulation ; biofilm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple model was presented to describe the time courses of citric acid production by a rotating disc contactor (RDC) using Aspergillus niger. The model is expressed by Monod-type cell growth, Luedeking-Piret-type citric acid production rate equations, and the diffusion equation for oxygen in the biofilm. The model contains five parameters which were determined by the nonlinear least squares method by fitting the numerical solution to the experimental data. In solving the equations, the cell density of the biofilm was estimated from the value of cellular mass per unit of biofilm area using an empirical equation. The experimental time courses in citric acid production period were well simulated with this model. The relation between the specific biofilm surface area and the rate of citric acid production was also explained by the simulation using the average values of five parameters of twelve runs. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 689-696, 1997.
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    Activity of an isothiazolone biocide against Hormoconis resinae in pure and mixed biofilms (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 395-397 
    Details
    ISSN: 1573-0972
    Keywords: Biocide ; biofilm ; Hormoconis ; immunofluorescence ; Kathon FP ; stainless steel ; sulphate-reducing bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biofilms containing single or mixed cultures of the fungus Hormoconis resinae and anaerobic sulphate-reducing bacteria (SRB) on stainless steel were incubated with an isothiazolone biocide (Kathon FP) at 28°C for 24 h. H. resinae within the biofilm was enumerated by immunofluorescence microscopy using specific antiserum, and SRB were assayed by culture. Fungal numbers in mixed biofilms were considerably reduced in comparison with those in pure biofilms. The biocide was shown to be effective against H. resinae in pure biofilms at 50 and 100 ppm, but in mixed biofilms only at the higher concentration. This concentration also reduced the sessile SRB numbers by 99%.
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    URL: http://dx.doi.org/10.1007/BF00340218
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    Continuous ethanol production byZymomonas mobilis andSaccharomyces cerevisiae in biofilm reactors (1996)
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 249-256 
    Details
    ISSN: 1476-5535
    Keywords: ethanol ; biofilm ; plastic composite-supports ; Zymomonas ; Saccharomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Continuous ethanol fermentations were performed in duplicate for 60 days withZymomonas mobilis ATCC 331821 orSaccharomyces cerevisiae ATCC 24859 in packed-bed reactors with polypropylene or plastic composite-supports. The plastic composite-supports used contained polypropylene (75%) with ground soybean-hulls (20%) and zein (5%) forZ. mobilis, or with ground soybean-hulls (20%) and soybean flour (5%) forS. cerevisiae. Maximum ethanol productivities of 536 gL−1 h−1 (39% yield) and 499 gL−1 h−1 (37% yield) were obtained withZ. mobilis on polypropylene and plastic composite-supports of soybean hull-zein, respectively. ForZ. mobilis, and optimal yield of 50% was observed at a 1.92h−1 dilution rate for soybean hull-zein plastic composite-supports with a productivity of 96gL−1h−1, whereas with polypropylene-supports the yield was 32% and the productivity was 60gL−1h−1. With aS. cerevisiae fermentation, the ethanol production was less, with a maximum productivity of 76gL−1h−1 on the plastic composite-support at a 2.88h−1 dilution rate with a 45% yield. Polypropylene-support bioreactors were discontinued due to reactor plugging by the cell mass accumulation. Support shape (3-mm chips) was responsible for bioreactor plugging due to extensive biofilm development on the plastic composite-supports. With suspensionculture continuous fermentations in continuously-stirred benchtop fermentors, maximum productivities of 5gL−1h−1 were obtained with a yield of 24 and 26% withS. cerevisiae andZ. mobilis, respectively. Cell washout in suspensionculture continuous fermentations was observed at a 1.0h−1 dilution rate. Therefore, for continuous ethanol fermentations, biofilm reactors out-performed suspension-culture reactors, with 15 to 100-fold higher productivities (gL−1h−1) and with higher percentage yields forS. cerevisiae andZ. mobilis, respectively. Further research is needed with these novel supports to evaluate different support shapes and medium compositions that will permit medium flow, stimulate biofilm formation, reduce fermentation costs, and produce maximum yields and productivities.
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    Variation in sessile microflora during biofilm formation on AISI-304 stainless steel coupons (1996)
    Springer
    Journal of industrial microbiology and biotechnology 17 (1996), S. 6-10 
    Details
    ISSN: 1476-5535
    Keywords: biofilm ; cooling water ; microbiologically influenced corrosion ; microbial fouling ; stainless steel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Coupons of stainless steel type AISI-304 were exposed to the industrial cooling system of a petrochemical plant fed by seawater from the Guanabara Bay, Rio de Janeiro, Brazil, in order to study thein situ formation of biofilms. Bacteria, microalgae and fungi were detected on the coupons as soon as 48 h after exposure. Their respective numbers were determined at times 48, 96 and 192 h and over the following 8 weeks. Aerobic, anaerobic and sulfate-reducing bacteria were quantified according to the technique of the most probable number, and fungi by the pour plate technique. The number of microorganisms present in the forming biofilm varied over the experimental period, reaching maximal levels of 14×1011 cells cm−2, 30×1013 cells cm−2, 38×1011 cells cm−2 and 63×105 cells cm−2, respectively, for aerobic bacteria, anaerobic bacteria, sulfate-reducing bacteria and fungi, and the dynamics of this variation depended on the group of microorganisms.Bacillus sp,Escherichia coli, Serratia sp andPseudomonas putrefaciens were identified among the aerobic bacteria isolated. Additionally, microalgae and bacteria of the genusGallionella were also detected. Nonetheless, no evidence of corrosion was found on the stainless steel type AISI-304 coupons over the experimental period.
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    A dual fluorescence technique for visualization ofStaphylococcus epidermidis biofilm using scanning confocal laser microscopy (1996)
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 48-56 
    Details
    ISSN: 1476-5535
    Keywords: Staphylococcus epidermidis ; biofilm ; laser scanning confocal microscopy ; slime ; lectin marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new dual fluorescence technique is described which, when combined with scanning confocal laser microscopy (SCLM), can be used to visualize the components of biofilm produced byStaphylococcus epidermidis. Chemostat cultures of RP62A (a well-characterized slime-producing strain ofS. epidermidis) were used to produce mature biofilm on polyvinylcholoride (PVC) disks immobilized in a modified Robbins device using a ‘seed’ and ‘feed’ model system. Serial horizontal and vertical optical thin sections, as well as three-dimensional computer reconstructions, were obtained onin situ biofilm using the dual fluorescence procedure. Bacteria were visualized by green autofluorescence excited at 488 nm with an Argon laser. Cell-associated and exocellular matrix material (slime) was visualized by red fluorescence excited at 568 nm with a Krypton laser after interaction of the biofilm with Texas Red-labeled wheat germ agglutinin which is a slime-specific lectin marker. Structural analysis revealed that the cocci grew in slime-embedded cell clusters forming distinct conical-shaped microcolonies. Interspersed open channels served to connect the bulk liquid with the deepest layers of the mature, hydrated biofilm which increased overall surface area and likely facilitated the exchange of nutrients and waste products throughout the biofilm. The combined dual fluorescence technique and SCLM is potentially useful as a specific noninvasive tool for studying the effect of antimicrobial agents on the process of biofilm formation and for the characterization of the architecture ofS. epidermidis biofilm formedin vivo andin vitro on medical grade virgin or modified inert polymer surfaces.
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    Evaluation of plastic composite-supports for enhanced ethanol production in biofilm reactors (1996)
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 241-248 
    Details
    ISSN: 1476-5535
    Keywords: ethanol ; biofilm ; Zymomonas ; Saccharomyces ; Streptomyces ; plastic composite-supports
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biofilms are a natural form of cell immobilization that result from microbial attachment to solid supports. Biofilm reactors with polypropylene composite-supports containing up to 25% (w/w) of various agricultural materials (corn hulls, cellulose, oat hulls, soybean hulls or starch) and nutrients (soybean flour or zein) were used for ethanol production. Pure cultures ofZymomonas mobilis, ATCC 31821 orSaccharomyces cerevisiae ATCC 24859 and mixed cultures with either of these ethanol-producing microorganisms and the biofilm-formingStreptomyces viridosporus T7A ATCC 39115 were evaluated. An ethanol productivity of 374g L−1 h−1 (44% yield) was obtained on polypropylene composite-supports of soybean hull-zein-polypropylene by usingZ. mobilis, whereas mixed-culture fermentations withS. viridosporus resulted in ethanol productivity of 147.5 g L−1 h−1 when polypropylene composite-supports of corn starch-soybean flour were used. WithS. cerevisiae, maximum productivity of 40 g L−1 h−1 (47% yield) was obtained on polypropylene composite-supports of soybean hull-soybean flour, whereas mixed-culture fermentation withS. viridosporus resulted in ethanol productivity of 190g L−1 h−1 (35% yield) when polypropylene composite-supports of oat hull-polypropylene were used. The maximum productivities obtained without supports (suspension culture) were 124 g L−1 h−1 and 5 g L−1 h−1 withZ. mobilis andS. cerevisiae, respectively. Therefore, forZ. mobilis andS. cerevisiae, ethanol productivities in biofilm fermentations were three- and eight-fold higher than suspension culture fermentations, respectively. Biofilm formation on the chips was detected by weight change and Gram staining of the support material at the end of the fermentation. The ethanol production rate and concentrations were consistently greater in biofilm reactors than in suspension cultures.
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    Diversity in surface colonization behavior in marine bacteria (1996)
    Springer
    Journal of industrial microbiology and biotechnology 17 (1996), S. 228-234 
    Details
    ISSN: 1476-5535
    Keywords: colonization ; biofilm ; diversity ; proximal vertical packing ; cell-cell interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Using laminar flow chambers and time-lapse video imaging, colonization of surfaces by four marine bacteria revealed a diverse range of morphological characteristics and cell-cell interactions. The strain SW5 formed a compact, multilayered single- and double-cell biofilm on hydrophobic surfaces but developed long multicellular chains on hydrophilic surfaces. The morphologically similar SW8 showed unusual proximal vertical packing of cells on both substrata.Vibrio sp strain S14 exhibited cyclical colonization-detachment events on both substrata.Pseudomonas sp strain S9 initially displayed reversible and then irreversible adhesion apparently triggered by a cell density phenomenon that led to the development of regular microcolonies on both substrata with individual cells translocating between the colonies. The length of time bacteria were exposed to and their density at a surface influenced behavioral traits, with diverse and distinctive species-specific behavioral events.
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    Transport limitation of chlorine disinfection of Pseudomonas aeruginosa entrapped in alginate beads (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 93-100 
    Details
    ISSN: 0006-3592
    Keywords: disinfection ; chlorine ; transport ; gel bead ; biofilm ; reaction-diffusion ; Pseudomonas aeruginosa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An artificial biofilm system consisting of Pseudomonas aeruginosa entrapped in alginate and agarose beads was used to demonstrate transport limitation of the rate of disinfection of entrapped bacteria by chlorine. Alginate gel beads with or without entrapped bacteria consumed chlorine. The specific rate of chlorine consumption increased with increasing cell loading in the gel beads and decreased with increasing bead radius. The value of an observable modulus comparing the rates of reaction and diffusion ranged from less than 0.1 to 8 depending on the bead radius and cell density. The observable modulus was largest for large (3-mm-diameter) beads with high cell loading (1.8 × 109 cfu/cm3) and smallest for small beads (0.5 mm diameter) with no cells added. A chlorine microelectrode was used to measure chlorine concentration profiles in agarose beads (3.0 mm diameter). Chlorine fully penetrated cell-free agarose beads rapidly; the concentration of chlorine at the bead center reached 50% of the bulk concentration within approximately 10 min after immersion in chlorine solution. When alginate and bacteria were incorporated into an agarose bead, pronounced chlorine concentration gradients persisted within the gel bead. Chlorine did gradually penetrate the bead, but at a greatly retarded rate; the time to reach 50% of the bulk concentration at the bead center was approximately 46 h. The overall rate of disinfection of entrapped bacteria was strongly dependent on cell density and bead radius. Small beads with low initial cell loading (0.5 mm diameter, 1.1 × 107 cfu/cm3) experienced rapid killing; viable cells could not be detected (〈1.6 × 105 cfu/cm3) after 15 min of treatment in 2.5 mg/L chlorine. In contrast, the number of viable cells in larger beads with a higher initial cell density (3.0 mm diameter, 2.2 × 109 cfu/cm3) decreased only about 20% after 6 h of treatment in the same solution. Spatially nonuniform killing of bacteria within the beads was demonstrated by measuring the transient release of viable cells during dissolution of the beads. Bacteria were killed preferentially near the bead surface. Experimental results were consistent with transport limitation of the penetration of chlorine into the artificial biofilm arising from a reaction-diffusion interaction. The methods reported here provide tools for diagnosing the mechanism of biofilm resistance to reactive antimicrobial agents in such applications as the treatment of drinking and cooling waters. © 1996 John Wiley & Sons, Inc.
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    Prevention of clogging in a biological trickle-bed reactor removing toluene from contaminated air (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 91-97 
    Details
    ISSN: 0006-3592
    Keywords: waste-gas treatment ; trickle-bed reactor ; fungi ; biofilm ; toluene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Removal of organic compounds like toluene from waste gases with a trickle-bed reactor can result in clogging of the reactor due to the formation of an excessive amount of biomass. We therefore limited the amount of nutrients available for growth, to prevent clogging of the reactor. As a consequence of this nutrient limitation a lower removal rate was observed. However, when a fungal culture was used to inoculate the reactor, the toluene removal rate under nutrient limiting conditions was higher. Over a period of 375 days, an average removal rate of 27 g C/(m3 h) was obtained with the reactor inoculated with the fungal culture. From the carbon balance over the reactor and the nitrogen availability it was concluded that, under these nutrient-limited conditions, large amounts of carbohydrates are probably formed. We also studied the application of a NaOH wash to remove excess biomass, as a method to prevent clogging. Under these conditions an average toluene removal rate of 35 g C/(m3 h) was obtained. After about 50 days there was no net increase in the biomass content of the reactor. The amount of biomass which was formed in the reactor equaled the amount removed by the NaOH wash. © 1996 John Wiley & Sons, Inc.
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    Steady-state solution of a two-species biofilm problem (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 675-686 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; steady state ; heterotrophs ; nitrosomonas ; nitrobacter ; model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Through a thorough investigation of the boundary conditions for a general two-species biofilm model, a simple and fast method for solving the steady-state case is developed and presented. The methods used may be extended to biofilm models in which more than two species are considered. Four different sets of boundary conditions are possible for the two-species biofilm model. Each set is shown to be asymptotically stable. A biofilm model describing the competition between autotrophic and heterotrophic bacteria and a biofilm model considering only Nitrosomonas and Nitrobacter are used for illustration. A parameter Lcrit, critical film thickness for bacterial coexistence, is introduced from which criteria on the bulk concentrations for coexistence are derived. From these criteria it is seen that the thinner the biofilm, the more restrictive the conditions are for steady-state coexistence. For thin biofilms there may, in many cases, be no point in considering more than one species in the biofilm model. Furthermore, the gradients of the bacterial concentrations are in many cases negligible in thin biofilms, and the biofilm may then be assumed to be homogeneous. The criteria on the bulk concentrations together with the four sets of boundary conditions provide the necessary information for a direct solution of the steady-state two-species biofilm model by means of an ordinary differential and algebraic equation solver. © 1996 John Wiley & Sons, Inc.
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    Modeling biocide action against biofilms (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 445-455 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; biocide ; disinfection ; reaction-diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A phenomenological model of biocide action against microbial biofilms was derived. Processes incorporated in the model include bulk flow in and out of a well-mixed reactor, transport of dissolved species into the biofilm, substrate consumption by bacterial metabolism, bacterial growth, advection of cell mass within the biofilm, cell detachment from the biofilm, cell death, and biocide concentration-dependent disinfection. Simulations were performed to analyze the general behavior of the model and to perform preliminary sensitivity analysis to identify key input parameters. The model captured several general features of antimicrobial agent action against biofilms that have been observed widely by experimenters and practitioners. These included (1) rapid disinfection followed by biofilm regrowth, (2) slower detachment than disinfection, and (3) reduced susceptibility of microorganisms in biofilms. The results support the plausibility of a mechanism of biofilm resistance in which the biocide is neutralized by reaction with biofilm constituents, leading to a reduction in the bulk biocide concentration and, more significantly, biocide concentration gradients within the biofilm. Sensitivity experiments and analyses identified which input parameters influence key response variables. Each of three response variables was sensitive to each of the five input parameters, but they were most sensitive to the initial biofilm thickness and next most sensitive to the biocide disinfection rate coefficient. Statistical regression modeling produced simple equations for approximating the response variables for situations within the range of conditions covered by the sensitivity experiment. The model should be useful as a tool for studying alternative biocide control strategies. For example, the simulations suggested that a good interval between pulses of biocide is the time to minimum thickness. © 1996 John Wiley & Sons, Inc.
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    Spatial microbial distributions of nitrifiers and heterotrophs in mixed-population biofilms (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 24-35 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; interspecies competition ; spatial microbial distribution ; heterotrophs ; nitrifiers ; microslicing ; model simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Spatial microbial distributions of nitrifiers and heterotrophs in undefined mixed-population biofilms were experimentally investigated using a microslicer technique and correlated with nitrification efficiency of the biofilm system. The general stratification of different bacterial groups in the biofilm was simulated using a one-dimensional (1-D) mathematical biofilm accumulation model (BAM) and compared with the experimental results. Biofilms were cultured at three C : N ratios of feed solutions in a partially submerged rotating biological contactor (RBC). It was shown that the biofilms were vertically stratified (from biofilm surface to substratum). At C : N = 0, heterotrophs and nitrifiers coexisted in the outermost biofilm and heterotrophs dominated in the innermost biofilm. At C : N = 1.5, heterotrophs outcompeted nitrifiers for dissolved oxygen and space; thus, heterotrophs dominated in the outermost biofilm and nitrifiers were present only in the deeper biofilm. Nitrifiers and heterotrophs coexisted in the innermost biofilm. An increase in the influent C : N ratio resulted in stronger stratification of microbial species, as well as inhibition of nitrification. In batch experiments, NH4—N utilization rate (RNH4—N) was almost the same at each substrate C : N ratio even though NH4 oxidizers were predominantly present in the deeper biofilm. The biofilm performance could not be sufficiently explained by the obtained microbial spatial distribution, suggesting that one-dimensional description of microbial distribution was not good enough and three-dimensional measurements of microbial spatial distribution is necessary. Total bacterial densities increased by a factor of 3-17 with biofilm depth. The metabolically active cell fraction decreased from 35 ± 13% in the outermost biofilm to 15 ± 4% in the innermost biofilm, presumably due to substrate limitation. The model predicted more pronounced stratification of nitrifiers and heterotrophs than the observed results. This discrepancy could be attributed to the real biofilms that were structurally heterogeneous (e.g., water channels), which could not be described by the one-dimensional model. The results of this study clearly indicate the limitation of 1-D biofilm models to describe the extent of stratification of nitrifiers and heterotrophs and suggest a 3-D model is necessary. © 1996 John Wiley & Sons, Inc.
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    Biological sulfate reduction using synthesis gas as energy and carbon source (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 136-144 
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    ISSN: 0006-3592
    Keywords: sulfate-reducing bacteria ; biofilm ; immobilization ; gas-lift reactor ; carbon monoxide ; synthesis gas ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biological sulfate reduction was studied in laboratory-scale gas-lift reactors. Synthesis gas (gas mixtures of H2/CO/CO2) was used as energy and carbon source. The required biomass retention was obtained by aggregation and immobilization on pumice particles. Special attention was paid to the effect of CO addition on the sulfate conversion rate, aggregation, and aggregate composition.Addition of 5% CO negatively affected the overall sulfate conversion rate; i.e., it dropped from 12-14 to 6-8 g SO2-4/L day. However, a further increase of CO to 10 and 20% did not further deteriorate the process. With external biomass recycling the sulfate conversion rate could be improved to 10 g SO2-4/L day. Therefore biomass retention clearly could be regarded as the rate-limiting step. Furthermore, CO affected the aggregate shape and diameter. Scanning electron microscopy (SEM) photographs showed that rough aggregates pregrown on H2/CO2 changed into smooth aggregates upon addition of CO. Addition of CO also changed the aggregate Sauter mean diameter (d32) from 1.7 mm at 5% CO to 2.1 mm at 20% CO. After addition of CO, a layered biomass structure developed. Acetobacterium sp. were mainly located at the outside of the aggregates, whereas Desulfovibrio sp. were located inside the aggregates. © 1996 John Wiley & Sons, Inc.
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    Mathematical modeling of mixed-culture biofilms (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 172-184 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; diffusion ; model ; mixed-culture ; simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: About 10 years ago a set of mass balance equations for mathematical modeling of mixed-culture biofilms (MCBs) was presented. That model was able to describe the progression of the biofilm thickness and the spatial distribution and development in time of particulate and dissolved components in the biofilm as a function of transport and transformation processes. Experimental observations made in the past years have shown that some of the assumptions made in that MCB model were too simple. Therefore, an extended MCB model with additional processes has been developed. This model includes a more flexible description of transport of dissolved components in the biofilm and considers diffusive transport of particulate components in the biofilm solid matrix, changes of the biofilm liquid phase volume fraction (porosity), and simultaneous detachment and attachment of cells and particles at the biofilm surface. The extended MCB model is implemented in AQUASIM, a new computer program designed for the analysis of aquatic systems, which is used here to illustrate and discuss the effect of the additional processes on MCB behavior. © 1996 John Wiley & Sons, Inc.
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    Physical and chemical characterization of the polysaccharide capsule of the marine bacterium,Hyphomonas strain MHS-3 (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 347-351 
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    ISSN: 1476-5535
    Keywords: polysaccharides ; bacterial capsule ; adhesion ; biofilm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hyphomonas MHS-3 is a biphasic, marine bacterium that synthesizes an exopolysaccharide (EPS) capsule, which has a role in attaching the adherent, prosthecate developmental stages to solid substrata. To correlate structure with function, we characterized this integral EPS. It has a relatively homogeneous molecular weight of approximately 60000 daltons, is acidic, and putatively contains large concentrations ofN-acetylgalactosamine (GalNAc). The theoretical identity of the anionic component of the polymer, and the similarities betweenHyphomonas MHS-3 EPS and other adhesive marine/aquatic bacterial EPS are discussed.
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    Interspecies bacterial interactions in biofilms (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 257-262 
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    ISSN: 1476-5535
    Keywords: bacteria ; interaction ; biofilm ; mixed-species ; community
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Interactions among bacterial populations can have a profound influence on the structure and physiology of microbial communities. Interspecies microbial interactions begin to influence a biofilm during the initial stages of formation, bacterial attachment and surface colonization, and continue to influence the structure and physiology of the biofilm as it develops. Although the majority of research on bacterial interactions has utilized planktonic communities, the characteristics of biofilm growth (cell positions that are relatively stable and local areas of hindered diffusion) suggest that interspecies interactions may be more significant in biofilms.
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    Structure, function and immunochemistry of bacterial exopolysaccharides (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 339-346 
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    ISSN: 1476-5535
    Keywords: polysaccharides ; bacterial capsule ; biofilm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract There has been much written on bacterial exopolysaccharides (EPS) and their role in virulence. Less has been published regarding EPS in free living species. This review focuses on that subject, emphasizing their functions in the environment and the use of antibody probes to study them.
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    Prevention of biofilm formation by polymer modification (1995)
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    Journal of industrial microbiology and biotechnology 15 (1995), S. 391-396 
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    ISSN: 1476-5535
    Keywords: biofilm ; prevention ; polymer modification ; glow discharge treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Bacterial biofilm formation on synthetic polymers plays an important role in industry and in modern medicine, leading, for example, to difficult-to-treat infections caused by colonized foreign bodies. Prevention of biofilm formation is a necessary step in the successful prophylaxis of such infections. One approach is to inhibit bacterial adherence by polymer surface modification. We have investigated polymer modification by glow discharge treatment in order to study the influence of the modified surface on bacterial adherence. Surface roughness, surface charge density and contact angles of the modified polymers were determined and related to the adherence ofStaphylococcus epidermidis KH6. Although no influence of surface roughness and charge density on bacterial adherence was noticed, a correlation between the free enthalpy of adhesion (estimated from contact angle measurements) and adherence was observed. There seems to exist a certain minimum bacterial adherence, independent of the nature of the polymer surface. Modified polymers with negative surface charge allow for bacterial adherence close to the adherence minimum. These polymers could be improved further by the ionic bonding of silver ions to the surface. Such antimicrobial polymers are able to prevent bacterial colonization, which is a prerequisite for biofilm formation. It is suggested that modification of polymers and subsequent surface coupling of antimicrobials might be an effective approach for the prevention of bacterial biofilm formation.
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    Continuous nondestructive monitoring of microbial biofilms: A review of analytical techniques (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 263-276 
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    ISSN: 1476-5535
    Keywords: biofilm ; on-line monitoring ; nondestructive monitoring ; microscopy ; Fourier-transform infrared spectrometry ; bioluminescence ; microelectrode ; quartz crystal microbalance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A fundamental requirement for the understanding and control of biofilms is the continuous nondestructive monitoring of biofilm processes. This paper reviews research analytical techniques that monitor biofilm processes in a continuous nondestructive manner and that could also be modified for industrial applications. To be considered ‘continuous’ and ‘nondestructive’ for the purpose of this review a technique must: (a) function in an aqueous system; (b) not require sample removal; (c) minimize signal from organisms or contaminants in the bulk phase; and (d) provide real-time data. Various microscopic, spectrochemical, electrochemical, and piezoelectrical analysis methods fulfill these criteria. These techniques monitor the formation of biofilms, the physiology of the microorganisms within biofilms, and/or the interaction of the biofilms with their environment. It is hoped that this review will stimulate development and use of biofilm monitoring techniques in industrial and environmental settings.
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    Lectin-biotin assay for slime present inin situ biofilm produced byStaphylococcus epidermidis using transmission electron microscopy (TEM) (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 156-161 
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    ISSN: 1476-5535
    Keywords: S. epidermidis ; biofilm ; slime ; lectin marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A lectin-biotin assay was developed for use in the specific detection of slime produced byStaphylococcus epidermidis RP62A and M187sp11 grown in a chemically defined medium. Mature biofilm was formed on polyvinylchloride (PVC) disks using a combined chemostat-modified Robbins device (MRD) model system. Specimens fixedin situ were: 1) stained with ruthenium red; 2) reacted overnight with biotin-labeled lectins (WGA, succinyl-WGA, Con A, or APA) followed by treatment with gold-labeled extravidin; or 3) reacted with antibodies againstS. epidermidis RP62A capsular polysaccharide/adhesin (PS/A) using an immunogold procedure. WGA and succinyl-WGA (S-WGA), which specifically bindN-acetylglucosamine, were shown by TEM to react only with slime, both cell-associated and exocellular. In contrast, Con A, APA and anti-PS/A reacted with the bacterial cell surface but did not react with slime. These results indicate the usefulness of WGA lectin as a specific marker for detection of the presence and distribution of slime matrix material inS. epidermidis biofilm.
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    Dental plaque as a biofilm (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 169-175 
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    ISSN: 1476-5535
    Keywords: dental plaque ; biofilm ; adhesion ; co-aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Dental plaque is the diverse microbial community found on the tooth surface embedded in a matrix of polymers of bacterial and salivary origin. Once a tooth surface is cleaned, a conditioning film of proteins and glycoproteins is adsorbed rapidly to the tooth surface. Plaque formation involves the interaction between early bacterial colonisers and this film (the acquired enamel pellicle). To facilitate colonisation of the tooth surface, some receptors on salivary molecules are only exposed to bacteria once the molecule is adsorbed to a surface. Subsequently, secondary colonisers adhere to the already attached early colonisers (co-aggregation) through specific molecular interactions. These can involve protein-protein or carbohydrate-protein (lectin) interactions, and this process contributes to determining the pattern of bacterial succession. As the biofilm develops, gradients in biologically significant factors develop, and these permit the co-existence of species that would be incompatible with each other in a homogeneous environment. Dental plaque develops naturally, but it is also associated with two of the most prevalent diseases affecting industrialised societies (caries and periodontal diseases). Future strategies to control dental plaque will be targeted to interfering with the formation, structure and pattern of development of this biofilm.
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    Formation of nitrifying biofilms on small suspended particles in airlift reactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 585-595 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; wastewater treatment ; airlift reactor ; nitrification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For a stable and reliable operation of a BAS-reactor a high, active biomass concentration is required with mainly biofilm-covered carriers. The effect of reactor conditions on the formation of nitrifying biofilms in BAS-reactors was investigated in this article. A start-up strategy to obtain predominantly biofilm-covered carriers, based on the balancing of detachment and a biomass production per carrier surface area, proved tp be very successful. The amount of biomass and the fraction of covered carrier were high and development of nitrification activity was fast, leading to a volumetric conversion of 5 kgN · m-3 · d-1 at a hydraulic retention time of 1h. A 1-week, continuous inoculation with suspended purely nitrifying microorganisms resulted in a swift start-up compared with batch addition of a small number of biofilms with some nitrification activity. The development of nitrifying biofilms was very similar to the formation of heterotrophic biofilms. In contrast to heterotrophic bio-films, the diameter of nitrifying biofilms increased during start-up. The detachment rate from nitrifying biofilms decreased with lower concentrations of bare carrier, in a fashion comparable with heterotrophic biofilms, but the nitrifying biofilms were much more robust and resistant. Standard diffusion theory combined with reaction kinetics are capable of predicting the activity and conversion of biofilms on small suspended particles. © 1995 John Wiley & Sons Inc.
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    Measurement of local mass transfer coefficient in biofilms (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 737-744 
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    ISSN: 0006-3592
    Keywords: biofilm ; mass transfer coefficient ; microelectrode ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Local mass transfer rates for an electrochemically formed microsink in an aerobic biofilm was measured by a mobile microelectrode using limiting current technique. Mass transfer coefficients varied both horizontally and vertically in the biofilm. The results implied the existence of an irregular biofilm structure consisting of microbial cell clusters surrounded by tortuous water channels. An unexpected increase of the local mass transfer coefficient just above the biofilm surface suggested the existence, of local flow instability in this region. As expected, the influence of bulk flow velocity on the local mass transfer rate decreased with increasing depth into the biofilm. Mass transfer coefficients fluctuated significantly inside microbial cell clusters, suggesting the existence of internal channels through which liquid could flow. A new conceptual model of biofilm microbial cluster structure is proposed to account for such biofilm microstructure irregularities. © 1995 John Wiley & Sons, Inc.
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    Detachment of biomass from suspended nongrowing spherical biofilms in airlift reactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 258-269 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; detachment ; abrasion ; breakage ; airlift reactor ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In three-phase internal loop airlift reactors, the detachment of biomass from suspended biofilm pellets in the presence of bare carrier particles was investigated under nongrowth conditions. The detachment rate was dominated by collisions between bare carrier particles and biofilm pellets. The concentration of bare carrier particles and the carrier roughness strongly influenced the detachment rate. A change in flow regime from bubbling to slug flow considerably increased the detachment rate. Otherwise, the superficial gas velocity did not directly affect the detachment rate. The influence of particle size was not clear. The bottom clearance did not affect the detachment rate within the tested range. Other aspects of reactor geometry might be important. The main detachment processes were abrasion and breakage of biofilm pellets. During the detachment process, two phases could be distinguished. In the first phase the detachment was relatively high, and both breakage and abrasion of biofilm pellets occurred. During the second phase, breakage dominated and the detachment rate was lower. The two-phase behavior is explained by differences in strength between the inner and outer biofilm layers, possibly caused by variations in local growth rates during biofilm formation. Differences in growth history might also explain the various detachment rates observed with different biofilm batches. © 1995 John Wiley & Sons, Inc.
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    Membrane bioreactor with a porous hydrophobic membrane as a gas-liquid contactor for waste gas treatment (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 107-115 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; waste gas treatment ; hydrophobic microporous membrane ; mass transfer ; propene ; Xanthobacter ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel type of bioreactor for waste gas treatment has been designed. The reactor contains a microporous hydrophobic membrane to create a large interface between the waste gas and the aqueous phase. To test the new reactor, propene was chosen because of its high air/water partition coefficient, which causes a low water concentration and hampers its removal from air. Propene transfer from air to a suspension of propene-utilizing Xanthobacter Py2 cells in the membrane bioreactor proved to be controlled by mass transfer in the liquid phase. The resistance of the membrane was negligible. Simulated propene transfer rates agreed well with the experimental data. A stable biofilm of Xanthobacter Py2 developed on the membrane during prolonged operation. The propene flux into the biofilm was 1 × 10-6 mol m-2 s-1 at a propene concentration of 9.3 × 10-2 mol m-3 in the gas phase. © 1995 John Wiley & Sons, Inc.
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    Quantitative analysis of biofilm thickness variability (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 503-510 
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    ISSN: 0006-3592
    Keywords: biofilm ; thickness ; heterogeneity ; roughness ; microscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thickness variability of biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae, and the binary population combination of these two species was quantified. The experimental method involved cryoembedding biofilms with a commercial tissue embedding agent, sectioning, and applying image analysis to construct thickness profiles along linear transects (up to 1 cm in length) across the substratum. Biofilms embedded and sectioned by this method were locally as thin as a single cell attached to the surface (〈5 μm) and as thick as 1000 μm. Week-old biofilms of three different species compositions displayed distinct structural features as indicated by their mean thicknesses and by a roughness coefficient. Monopopulation biofilms of P. aeruginosa (29 μm mean thickness) or K. pneumoniae (100 μm mean thickness) were thinner than the binary population biofilm (400 μm mean thickness). A roughness coefficient developed in this investigation corroborated the qualitative visual characterization of P. aeruginosa biofilms as relatively uniformly thick (mean roughness coefficient 0.15), K. pneumoniae biofilms as patchy (mean roughness coefficient 1.14), and the binary population biofilm as intermediate (mean roughness coefficient 0.26). Whereas P. aeruginosa and binary population biofilms covered the substratum completely, significant areas of essentially bare substratum were apparent in K. pneumoniae biofilms. The patchiness of K. pneumoniae biofilms may be due to the fact that this organism is nonmotile. A spatial correlation analysis of the thickness data indicated that thickness measurements were still correlated even when separated by distances that exceeded the mean biofilm thickness. Cell aggregates, some of them hundreds of microns in size, were observed in the effluent of K. pneumoniae and binary population biofilm reactors. Measurements of thickness variability and other observations reported in this article provide a quantitative basis for analysis of microscale structural heterogeneity of biofilms. © 1995 John Wiley & Sons, Inc.
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    Biofilm parameters influencing biocide efficacy (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 553-560 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; disinfection ; detachment ; biofouling ; ecology ; biocide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of biofilm areal cell density, species composition, and the presence of abiotic particles on the disinfection and removal of bacterial biofilms by monochloramine was investigated. Mono- and binary population biofilms of Pseudomonas aeruginosa and Klebsiella pneumoniae were grown on stainless-steel slides in a continuous flow annular reactor. Biofilms were treated in the reactor with a pulse/step dose of 4 mg/L monochloramine for 2 h. Biofilm samples were disaggregated and assayed for colony formation on R2A agar and for total cell numbers by acridine orange direct counts. These data were used to determine apparent first order rate coefficients for the processes of disinfection and detachment. Disinfection rate coefficients exceeded detachment rate coefficients by as much as an order of magnitude and the two coefficients were poorly correlated (r = 0.272). The overall decay rate coefficient (disinfection plus detachment) depended strongly on the initial biofilm areal cell density. It displayed a parabolic dependence on cell density with a maximum near 108 cfu/cm2. This result points to multiple factors influencing biofilm susceptibility to antimicrobial challenge. Decay rates of K. pneumoniae measured in binary population biofilms were comparable with those measured in monopopulation biofilms (p = 0.61). P. aeruginosa decayed more slowly in biofilsm dominated by K. pneumoniae (p = 0.028), indicating some interaction between species. The presence of kaolin and calcium carbonate particles in the biofilm reduced disinfection efficacy. © 1995 John Wiley & Sons, Inc.
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    Biological sulphate reduction using gas-lift reactors fed with hydrogen and carbon dioxide as energy and carbon source (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 586-594 
    Details
    ISSN: 0006-3592
    Keywords: sulphate-reducing bacteria ; biofilm ; granulation ; gas-lift reactor ; hydrogen sulphide toxicity ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Feasibility and engineering aspects of biological sulphate reduction in gas-lift reactors were studied. Hydrogen and carbon dioxide were used as energy and carbon source. Attention was paid to biofilm formation, sulphide toxicity, sulphate conversion rate optimization, and gasliquid mass transfer limitations. Sulphate-reducing bacteria formed stable biofilms on pumice particles. Biofilm formation was not observed when basalt particles were used. However, use of basalt particles led to the formation of granules of sulphate-reducing biomass. The sulphate-reducing bacteria, grown on pumice, easily adapted to free H2S concentrations up to 450 mg/L. Biofilm growth rate then equilibrated biomass loss rate. These high free H2S concentrations caused reversible inhibition rather than acute toxicity. When free H2S concentrations were kept below 450 mg/L, a maximum sulphate conversion rate of 30 g SO42-/L · d could be achieved after only 10 days of operation. Gas-to-liquid hydrogen mass transfer capacity of the reactor determined the maximum sulphate conversion rate. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260440505
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    Formation and growth of heterotrophic aerobic biofilms on small suspended particles in airlift reactors (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 595-608 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; aerobic waste water treatment ; airlift reactor ; waste water ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start-up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start-up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start-up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt-maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 ± 0.08 C-mol/C-mol, the maintenance value 0.019 ± 0.012 C-mol/(C-mol h). The lowest actual biomass yield measured in this study was 0.15 C-mol/C-mol. © 1994 John Wiley & Sons, Inc.
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    Heterogeneity of biofilms in rotating annular reactors: Occurrence, structure, and consequences (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 194-204 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; biofilm reactors ; structure ; heterogeneity ; kinetics ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rotating annular reactor (Roto Torque) was used for qualitative and quantitative studied on biofilm heterogeneity. In contrast to the classic image of biofilms as smooth, homogeneous layers of biomass on a substratum, studies using various pure and mixed cultures consistently revealed more-dimensional structures that resembled dunes and ridges, among others. These heterogeneities were categorized and their underlying causes analyzed. Contrary to expectations, motility of the microorganisms not a decisive factor in determining biofilm homogeneity. Small Variations in substratum geometry homogeneity. Small variations in substratum geometry and flow patterns were clearly reflected in the biofilm pattern. Nonhomogeneous flow and shear patterns in the reactor, together with inadequate mixing resulted in significant, position-dependent differences in surface growth. It was therefore not possible to take representative samples of the attached biomass. Like many other types of reactors, the Roto Torque reactor is valuable for qualitative and morphological biofilm experiments but less suitable for quantitative physiological and kinetics studies using attached microorganisms. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260440208
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    The existence of a biological equilibrium in a trickling filter for waste gas purification (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1279-1287 
    Details
    ISSN: 0006-3592
    Keywords: waste gas ; trickling filter ; biofilm ; dichlo-romethane ; biofiltration ; air pollution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Clogging is well-known phenomenon in the application of a biological tricking filter for both waste gas and wastewater treatment. Nevertheless, no such observations or even significant changes in pressure drop have ever been recorded during the long-term processing of a waste gas containing dichloromethane (DCM) as a sole carbon source. To obtain more information about this phenomenon, a detailed investigation into the carbon balance of this system has been performed. During a period of operation of about 200 days the rate of DCM elimination and the overall rate of CO2 production in a continuously operating filter were therefore recorded daily, thus allowing an evaluation of the overall conversion process. Furthermore pseudo-steady-state measurements were carried out on a regular basis. These experiments reveal more detailed information on the actual DCM conversion by Hyphomicrobium GJ21 within the biofilm. The combined results of the experiments described in this article show that on an overall basis a so-called biological equilibrium, i.e., a situation of no net biomass accumulation, is obtained in the course of time. It appeared that the overall rate of CO2 production slowly increased until, after some 200 days, it finally counter-balanced the conversion rate of DCM on a molar-basis. As opposed to this result, all pseudo-steady-state experiments indicated that about 60% of the eliminated primary carbon source is converted into biomass. This is in good agreements with results from microkinetic experiments. Based on these results and evaluation of the experimental data, it is concluded that interactions between several microbial populations are involved in this biological equilibrium. These interactions include both biomass growth and biomass degradation. © 1994 John Wiley & Sons, Inc.
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    Interactions of microbial biofilms with toxic trace metals: 2. Prediction and verification of an integrated computer model of lead (II) distribution in the presence of microbial activity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 232-239 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; extracellular biopolymer ; lead microbe interaction ; metal toxicity ; structured models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The interfacial interactions of a toxic trace metal, Pb, with a surface modified by a marine film-forming bacterium, Psedomonas atlantica, were predicted by a structured biofilm model used in conjunction with a chemical speciation model. The validity of the integrated model was tested for batch and continuous operations. Dynamic responses of the biophase due to transient lead concentration increases were also stimulated. The reasonable pre dictions achieved by the model demonstrate its utility in describing trace metal distributions in complex systems where the adsorption properties of inorganic surfaces are modified by adherent bacteria production of extracellular polymers. © 1994 John Wiley & Sons, Inc.
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    Solids retention time in spherical biofilms in a biofilm airlift suspension reactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 867-879 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; microbeads ; solids retention time ; airlift reactor ; particulates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluorescent microparticles were used as tracer beads to measure the dynamics of solids in spherical biofilms in a biofilm airlift suspension reactor. Attachment to, release from, and penetration into the biofilms of the tracer beads were measured. The coverage of the biofilm surface was low and the steady state particle concentration on the surface was dependent on the biofilm surface characteristics. The measured attachment rate constant was identical in both experiments and appeared to be determined by the hydrodynamic conditions in the turbulent reactor. The attachment rate was much faster than the release rate of the tracer beads and, therefore, the solidsretention time in the biofilm particle is not due to a simple reversible adsorption-desorption process. The heterogeneity of the distribution oftracer beads on different sectors on the biofilm surface decreased duringthe attachment period. Due to random detachment processes the heterogeneity of the tracer bead distribution increased during the release periodThe tracer beads quickly penetrated into the biofilm and became distributed throughout the active layer of the biofilm. The observed penetration into biofilms, the nonuniform distribution on the biofilm surface, and the fast uptake and slow release of tracer beads cannot be described by a simple model based on a reversible adsorption-desorption mechanism, nor withexisting biofilm models. These biofilm models, which balance growth and advection assuming a uniform biofilm with a homogeneous surface, are inadequate for the description of the observed solids retention time in biofilms. Therefore, a new concept of biofilm dynamics is proposed, in which formation of cracks and fissures, which are rapidly filled with growing biomass, combined with nonuniform local detachment, explains the observed fast penetration into the biofilm of tracer beads, the long residence time, and the nonuniform distibution of fluorescent microparticles. © 1994 John Wiley & Sons, Inc.
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    Liquid flow in heterogeneous biofilms (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 636-641 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; hydrodynamics ; mass transport ; particle tracking ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liquid flow was studied in aerobic biofilms, consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. Fluorescein microinjection was used as a qualitative technique to determine the presence of flow in cell clusters and voids. Flow velocity profiles were determined by tracking fluorescent latex spheres using confocal microscopy. Liquid was flowing through the voids and was stagnant in the cell clusters. Consequently, in voids both diffusion and convection may contribute to mass transfer, whereas in cell clusters diffusion is the dominant factor. The flow velocity in the biofilm depended on the average flow velocity of the bulk liquid. The velocity profiles in biofilms were linear and the velocity was zero at the substratum surface. The velocity gradients within biofilms were 50% of that near walls without biofilm coverage. The influence of the biofilm roughness on the flow velocity profiles was similar to that caused by rigid roughness elements. © 1994 John Wiley & Sons, Inc.
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    Interactions of microbial biofilms with toxic trace metals: 1. Observation and modeling of cell growth, attachment, and production of extracellular polymer (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 219-231 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; structured models ; extracellular biopolymer ; microbial attachment/detachment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adsorbent surfaces in natural and engineered systems are frequently modifies by bacterial attachment, growth of a biofilm, and bacterial production of extracellular polymer. Attached cells or sorbed polymers may alter the metal-binding characteristics of the supporting substratum and influence metal partitioning. The interdependent behavior of toxic trace metal partitioning and biofilm development requires description of the interaction between cell growth with its accompanying polymer production and metal speciation. In this article, the first of a two part series, a mechanistic model is developed to describe the growth of a film-forming bacterium which adheres to a substratum through the production of extracellular biopolymers. Each bacterial cell was modeled as a two-component structure consisting of active cell mass and biopolymer. The biopolymer component was further divided into cell-associated and dissolved categories to distinguish which remained naturally bound to cell surfaces from that which did not. Use of this structured model permitted independent description of the dynamics of cell growth, and polymer production, both of which may influence trace metal behavior. Employing parameters obtained from independent experiments as well as published values, the model satisfactorily predicts experimental observations of bacterial growth, attachment and detachment, biopolymer production, and adsorption of polymer onto solid (glass) surfaces. The model stimulated transient and steady-state biofilm systems equally well. In the second article in this series, we describe how this model may be extended and utilized to make predictions of the behavior of transient and steady-state biofilm systems in the presence of a toxic transition metal(Pb). © 1994 John Wiley & Sons, Inc.
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    Intrinsic fermentation kinetics of lactose in acidogenic biofilms (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 479-488 
    Details
    ISSN: 0006-3592
    Keywords: acidogenesis kinetics ; lactose ; lactose ; biofilm ; mass transfer resistance ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intrinsic fermentation kinetics of lactose in acidogenic biofilms were investigated in situ in a continuous flow fermentor at 35°C and pH 4.6. The external and internal mass transfer resistances to lactose molecules from bulk solution to inside the biofilms were experimentally minimized or eliminated in a thin biofilm and recycled medium. In a chemically defined culture medium, the immobilized acidogens converted lactose mainly to acetate and butyrate; the minor products included ethanol. propionate, lactate, and hydrogen. The utilization rate of lactose, as a function of lactose concentration in the fermentor, can be described by a Michaelis-Menten equation, as can the formation rates of acetate, butyrate, and ethanol. The production rates of propionate and lactate had a liner relationship with lactose concentration under the experimental conditions. The low pH (4.6) of culture medium could depress the formation of propionate, and intermediate which is most difficulty digested by acetogenic bacteria located in the second fermentor in a two-phase process. Production rate of acetate quickly reached a constant, and additional utilization of lactose produced more butyrate and other minor products. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260410412
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    Transport of 1-μm latex particles in pseudomonas aeruginosa biofilms (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 111-117 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; particle ; Pseudomonas aeruginosa ; transport ; roughness ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluorescent latex microbeads added to a Pseudomonas aeruginosa biofilm as tracers of particle movement penetrated the biofilm and remained in it much longer than predicted by a model of advective displacement due to cell growth. Beads with a nominal diameter of 1 μm that were added in the bulk fluid became distributed throughout the biofilm depth. Some microbeads penetrated to the substratum within the 24-h bead addition period. The biofilms had a mean thickness of approximately 34 μm but have been previously shown to be quite rough. Measured rates of bead release from the biofilm corresponded to first order time coefficients of 0.01-0.03 h-1. These bead release rates were approximately an order of magnitude less than the predicted time scale of advective transport, which is just the experimentally measured specific cellular growth rate of 0.15 h-1. Computer simulations of bead transport using the biofilm model BIOSIM were compared with bead release rate data and with bead position distributions within the biofilm as determined by microscopic examination of thin cross sections of embedded biofilm. The model predicted much faster release of beads from the biofilm than actually occurred. It is hypothesized that both the ability of beads to penetrate the biofilm and the unexpectedly low advective displacement velocity of particles in the biofilm were due to the rough nature of the biofilm. © 1993 John Wiley & Sons, Inc.
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    A model of biofilm detachment (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 111-117 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; detachment ; model ; physiology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general mathematical framework for modeling biofilm detachment is presented. The approach is founded on a material balance on biomass that equates the detachment rate to the product of a detachment frequency and a detaching particle mass. The model provides a theoretical basis for deriving many of the empirical detachment rate expressions in common use and can thus lend some insight into their physical and biological significance. By allowing for variation in the detachment frequency with depth in the biofilm, the model permits derivation of detachment expressions that reflect a dependence on chemical or physiological gradients in the biofilm. Analysis of literature data sets from two different biofilm systems suggests, in both cases, that detachment is a growth-associated phenomenon. © 1993 John Wiley & Sons, Inc.
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    Plasmid retention and gene expression in suspended and biofilm cultures of recombinant Escherichia coli DH5α(pMJR1750) (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 211-220 
    Details
    ISSN: 0006-3592
    Keywords: plasmid retention ; gene expression ; biofilm ; β-galactosidase ; segregational instability ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differences in plasmid retention and expression are studied in both suspended and biofilm cultures of Escherichia coli DH5α(PMJR1750). An alternative mathematical model is proposed which allows the determination of plasmid loss probability in both suspended batch and continuously fed biofilm cultures. In our experiments, the average probability of plasmid loss of E. coli DH5α(pMJR1750) is 0.0022 in batch culture in the absence of antibiotic selection pressure and inducer. Under the induction of 0.17 MM IPTG, the maximum growth rate of plasmid-bearing cells in suspended batch culture dropped from 0.45 h-1 to 0.35 h-1 and the β-galactosidase concentration reached an experimental maximum of 0.32. pg/cell 4 hours after the initiation of induction. At both 0.34 and 0.51 mM IPTG, growth rates in batch cultures decreased to 0.16 h-1, about 36% of that without IPTG, and the β-galactosidase concentration reached an experimental maximum of 0.47 pg/cell 3 hours after induction.In biofilm cultures, both plasmid-bearing and plasmid-free cells in increase with time reaching a plateau after 96 hours n the absence of both the inducer and any antibiotic selection pressure. Average probability of plasmid loss for biofilm-bound E. coli DH5β(pMJR1750) population was 0.017 without antibiotic selection. Once the inducer IPTG was added, the concentration of plasmid-bearing cells in biofilm dropped dramatically while plasmid-free cell numbers maintained unaffected. The β-galactosidase concentration reached a maximum in all biofilm experiments 24 hours after induction; they were 0.08, 0.1, and 0.12 pg/cel under 0.17, 0.34, and 0.51 mM IPTG, respectively. © 1993 John Wiley & Sons, Inc.
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    A statistical analysis of the effect of substrate utilization and shear stress on the kinetics of biofilm detachment (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 728-735 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; shear stress ; substrate loading ; biofilm detachment ; Pseudomonas aeruginosa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the least understood processes affecting biofilm accumulation is detachment. Detachment is the removal of cells and cell products from an established biofilm and subsequent entrainment in the bulk liquid. The goal of this research was to determine the effects of shear stress and substrate loading rate on the rate of biofilm detachment.Monopopulation Pseudomonas aeruginosa and undefined mixed population biofilms were grown on glucose in a RotoTorque biofilm reactor. Three levels of shear stress and substrate loading rate were used to determine their effects on the rate of detachment. Suspended cell concentrations were monitored to determine detachment rates, while other variables were measured to determine their influence on the detachment rate. Results indicate that detachment rate is directly related to biofilm growth rate and that factors which limit growth rate will also limit detachment rate. No significant influence of shear on detachment rate was observed.A new kinetic expression that incorporates substrate utilization rate, yield, and biofilm thickness was compared to published detachment expressions and gives a better correlation of data obtained both in this research and from previous research projects, for both mono- and mixed-population biofilms. © John Wiley & Sons, Inc.
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    Development and experimental evaluation of a steady-state, multispecies biofilm model (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 914-922 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; competition ; modeling ; multispecies ; nitrification ; species distribution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A steady-state model for quantifying the space competition in multispecies biofilms is developed. The model includes multiple active species, inert biomass, substrate utilization and diffusion within the biofilm, external mass transport, and detachment phenomena. It predicts the steady-state values of biofilm thickness, species distribution, and substrate fluxes. An experimental evaluation is carried out in completely mixed biofilm reactors in which slow-growing nitrifying bacteria compete with acetate-utilizing heterotrophs. The experimental results show that the model successfully describes the space competition. In particular, increasing acetate concentrations causes NH4+-N fluxes to decrease, because nitrifiers are forced deeper into the biofilm, where they experience greater mass-transport resistance.
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    An experimental study of mass diffusion and reaction rate in an anaerobic biofilm (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1141-1146 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; diffusion ; diffusivity ; immobilized cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental reactor consisting of two chambers, separated by a porous ceramic immobilization matrix, was constructed to measure the effective diffusivity of different compounds and the consumption rates of acetate in developing biofilms. In initial experiments, effective diffusivities for acetate, propionate, isopropanol, and lithium salt through the ceramic immobilization matrix in the absence of biofilm were determined to be 40% to 50% less than in water at infinite dilution. The effective diffusivity of the lithium salt was similar to that of acetate. The effective diffusivity of the lithium salt through biofilms of thickness in the range of 200 to 1200 μm was essentially constant with a value of approximately 7% of that in water at infinite dilution. Acetate consumption in the biofilm was linearly proportional to biofilm thickness up to a biofilm depth of 800 μm. Deviation from linearity appeared in biofilm thicknesses greater than 800 μm. Results of these experiments support previous reports that immobilized cell reactors have significantly higher bioconversion rates than suspended cell systems.
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    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260391110
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    Methanotrophic attached-film reactor development and biofilm characteristics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1218-1232 
    Details
    ISSN: 0006-3592
    Keywords: methanotroph ; biofilm ; fluidized-bed ; attached-film ; film thickness ; film density ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of using methanotrophs in an attached-film, fluidized-bed (MAFFB) reactor system has been under investigation since 1987. Mixed culture, methane-utilizing attached biofilms were developed on diatomaceous earth particles and on granular activated carbon. The required feed gases, methane and oxygen, were supplied to the attached biofilm in disolved form using separate gas-liquid aeration columns. Biofilm growth was steady despite low influent dissolved methane concentrations (1 to 3 mg/L). A breeder MAFFB operated consistently for 4.1 years with attached biofilm concentrations as high as 51.7 g VS/L static-bed with minimal biomass wasting and with minimal buffer and nutrient inputs. The maximum biomass concentration observed was 75.6 g VS/L static-bed in a MAFFB reactor treating trichloroethene. Biofilm thickness reached 160 μm with typical values of 70 μm under methane and oxygen growht-rate-limited conditions. Biofilm densities of 120 to 190 g VS/L film were observed. Growth rates varied from 〈0.01/d to 0.17/d. Greater than 90% of the biomass concentration in the bed was attached, and effluent total suspended solids ranged from 5 to 74 mg/L, with an average of 24 mg/L over 27 runs in four MAFFB systems at upflow velocities of 11.4 to 25 m/h. Heterotrophic attached-film methanotrophs appear to be stable and useful for applications in toxics treatment, and other product manipulations. © 1992 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260401012
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  • 70
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    Reaction kinetics in biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 877-882 
    Details
    ISSN: 0006-3592
    Keywords: microtechnique ; microprobe ; biofilm ; dissolved oxygen concentration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel in situ microtechnique allows evaluating parameters of diffusion-controlled reactions in biofilms. A microprobe, 15 μm in diameter, was used to simultaneously measure the dissolved oxygen concentration and the optical density at different depths in a submerged biofilm. Based on the results, the biofilm diffusion coefficient for dissolved oxygen, Df the dissolved oxygen flux through the biofilm surface, J02, and the half velocity coefficient, Ks, have been calculated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380809
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  • 71
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    Effective diffusivities of volatile fatty acids in methanogenic biofilms
    Amsterdam : Elsevier
    Bioresource Technology 48 (1994), S. 155-161 
    Details
    ISSN: 0960-8524
    Keywords: Effective diffusivity ; anaerobic digestion ; biofilm ; bioflocs ; fatty acids ; methane ; reaction-diffusion
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0960-8524(94)90203-8
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    Characterization of accumulated biomass in anaerobic filter treating various types of substrates
    Amsterdam : Elsevier
    Bioresource Technology 47 (1994), S. 275-282 
    Details
    ISSN: 0960-8524
    Keywords: Anaerobic filter ; acetate ; biofilm ; biomass ; egg albumin ; glucose ; growth yield ; methane production ; two-phase process
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0960-8524(94)90191-0
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