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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of local mass transfer coefficient in biofilms (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 737-744 
    Details
    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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480623
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological and chemical gradients in a Pseudomonas putida 54G biofilm degrading toluene in a flat plate vapor phase bioreactor (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 361-371 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; bioremediation ; toluene ; vapor phase bioreactors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Pseudomonas putida 54G biofilm was grown on toluene vapor supplied as the sole external carbon and energy source in a flat plate biofilm reactor. Enumerations of cells in the biofilm were made using culture techniques (selective and nonselective for toluene) and microscopic techniques (total and respiring cells), and an analysis of the progression of the state of the culture was made by examination of various fractions of the populations. Long-term exposure to higher levels of toluene produced the following trends: (i) lower fraction of total cells that respired; (ii) lower fraction of culturable cells that also grew on toluene; (iii) higher fraction of respiring cells that could not grow on toluene plates; and (iv) a relatively constant fraction of total cells that could not be cultured on toluene. Respiration rate was determined using oxygen microsensors, and the fraction of the total respiration that was not associated with toluene uptake increased with higher toluene exposure. A combination of cryosectioning and respiration rate data was used to demonstrate that more respiring cells and a higher respiration rate both occurred at the base of the film, suggesting a deterioration in physiological state with continued exposure to toluene. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 361-371, 1997.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Resistance of biofilms to the catalase inhibitor 3-amino-1,2,4-triazole (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 156-162 
    Details
    ISSN: 0006-3592
    Keywords: Pseudomonas aeruginosa ; Pseudomonas fluorescens ; Klebsiella pneumoniae ; 3-amino-1,2,4-triazole ; catalase ; hydrogen peroxide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Consortia of catalase positive bacteria consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae, in both the planktonic form and as biofilms, disproportionate hydrogen peroxide into oxygen and water. The biofilm, however, continued to disproportionate the hydrogen peroxide in the presence of the catalase inhibitor, 3-amino-1,2,4-triazole, while the planktonic organisms did not. While the bacterial catalase-peroxidase-dismutase system was probably responsible for the disproportionation of hydrogen peroxide in both cases, biofilms resisted inhibition of this enzyme system. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 156-162, 1998.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Iridium oxide pH microelectrode (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 601-608 
    Details
    ISSN: 0006-3592
    Keywords: pH measurement ; microelectrodes ; microenvironments ; biofilms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The manufacture, calibration, and signal conditioning during construction of an iridium/iridium oxide pH microsensor is described. The microsensor was designed to be used extracellularly, primarily in biofilm research. The sensing tip diameters were typically in the range of 3-15 μm. The iridium oxide was formed by potential cycling in dilute sulfuric acid. A pH profule across a denitrifying biofilm was measured as an example of an application. The higher Nernstian slope (70-80 mV/pH for fresh electrodes), increased rigidity, and restriction of the sensing tip to the outermost end of the electrode are features which make the iridium/iridium oxide pH microelectrode superior to a glass microelectrode. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400507
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusivity of Cu2+ in calcium alginate gel beads (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 755-760 
    Details
    ISSN: 0006-3592
    Keywords: biopolymers ; metal binding ; polymer-metal binding ; calcium alginate beads ; copper binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A linear absorption model (LAM) is used to describe the process of metal binding to spherically shaped biopolymers particles. The LAM was solved using a numerical algorithm which calculates diffusivities of metal ion in biopolymer gels. It assumes attainment of rapid metal-biopolymer binding equilibrium accompanied by rate limiting diffusion of the metal ions through the gel. The model was tested using batch experiments in which copper (Cu2+) binding with calcium alginate beads was investigated. Biopolymer density in the beads was varied between 2% and 5%. The diffusion coefficient of Cu2+ calculated from the LAM ranged from 1.19 × 10-9 to 1.48 × 10-9 m2 s-1 (average 1.31 ± 0.21 × 10-9 m2 s-1), independent of biopolymer density. The LAM has theoretical advantages over the shrinking core model (shell progressive model). The latter calculated an unreasonable exponential increase in the diffusion coefficient as density of alginate polymer in the bead increased. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410710
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of biofilm structures on oxygen distribution and mass transport (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1131-1138 
    Details
    ISSN: 0006-3592
    Keywords: confocal microscopy ; microelectrodes ; cell clusters ; pores ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. The oxygen distribution was strongly correlated with these strutures. The voids facilitated oxygen transport from the bulk liquid through the biofilm, supplying approximately 50% of the total oxygen consumed by the cells. The mass transport rate from the bulk liquid is influenced by the biofilm structure; the observed exchange surface of the biofilm is twice that calculated for a simple planar geometry. The oxygen diffusion occurred in the direction normal to the cluster surfaces, the horizontal and vertical components of the oxygen gradients were of equal importance. Consequently, for calculations of mass transfer rates a three-dimensional model is necessary. These findings imply that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431118
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of local diffusion coefficients in biofilms by microinjection and confocal microscopy (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 151-158 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; biofilm structure ; diffusivity ; mass transport in biofilms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new technique for the determination of local diffusion coefficients in biofilms is described. It is based on the microinjection of fluorescent dyes and quantitative analysis of the subsequent plume formation using confocal laser microscopy. The diffusion coefficients of fluorescein (MW 332), TRITC-IgG (MW 150000) and phycoerythrin (MW 240000) were measured in the cell clusters and interstitial voids of a heterogeneous biofilm. The diffusivities measured in the voids were close to the theoretical values in water. Fluorescein had the same diffusivity in cell clusters, voids, and sterile medium. TRITC-IgG did not diffuse in cell clusters, presumably due to binding to the cell cluster matrix. After treatment of the biofilm with bovine serum albumin, binding capacity decreased and the diffusion coefficient could be measured. The diffusivity of phycoerythrin in cell clusters was impeded by 41%, compared to interstitial voids. From the diffusion data of phycoerythrin it was further calculated that the cell cluster matrix had the characteristics of a gel with 0.6 nm thick fibers and pore diameters of 80 nm. © 1997 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    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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  • 9
    Electronic Resource
    Electronic Resource
    Microelectrode measurements of local mass transport rates in heterogeneous biofilms (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 302-309 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; microelectrodes ; local mass transfer coefficient ; effective diffusivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microelectrodes were used to measure oxygen profiles and local mass transfer coefficient profiles in biofilm clusters and interstitial voids. Both profiles were measured at the same location in the biofilm. From the oxygen profile, the effective diffusive boundary layer thickness (DBL) was determined. The local mass transfer coefficient profiles provided information about the nature of mass transport near and within the biofilm. All profiles were measured at three different average flow velocities, 0.62, 1.53, and 2.60 cm sec-1, to determine the influence of flow velocity on mass transport. Convective mass transport was active near the biofilm/liquid interface and in the upper layers of the biofilm, independent of biofilm thickness and flow velocity. The DBL varied strongly between locations for the same flow velocities. Oxygen and local mass transfer coefficient profiles collected through a 70 μm thick cluster revealed that a cluster of that thickness did not present any significant mass transport resistance. In a 350 μm thick biofilm cluster, however, the local mass transfer coefficient decreased gradually to very low values near the substratum. This was hypothetically attributed to the decreasing effective diffusivity in deeper layers of biofilms. Interstitial voids between clusters did not seem to influence the local mass transfer coefficients significantly for flow velocities of 1.53 and 2.60 cm sec-1. At a flow velocity of 0.62 cm sec-1, interstitial voids visibly decreased the local mass transfer coefficient near the bottom. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:302-309, 1998.
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  • 10
    Electronic Resource
    Electronic Resource
    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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