Browsing by Author "Abrahamson, Michael T."

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Development of an artificial biofilm to study the effects of a single microcolony on mass transport
(1996-07) Abrahamson, Michael T.; Lewandowski, Zbigniew; Geesey, Gill G.; Skjak-Braek, G.; Strand, W.
Alginate harvested from a mucoid strain of Pseudomonas aeruginosa, grown on YTG agar plates, was used to develop an artificial biofilm. The alginate was sterilized and fixed to a glass slide where it served as the biofilm matrix. High densities of P. aeruginosa were injected into specific locations within the alginate matrix to represent microcolonies similar to those found in natural biofilms. Dissolved oxygen microelectrodes, with tip diameters of 10 μm, were constructed and used to measure oxygen profiles through the artificial biofilm. Using mathematical models the kinetic parameters for microbial respiration were extracted from the profiles. The activity of immobilized microorganisms was monitored and the dynamics of dissolved oxygen transport to a single microcolony was evaluated.
Evaluation of a coupled mass transport-biofilm process model using dissolved oxygen microsensors
(1995) Cunningham, Alfred B.; Visser, Ernest Jay; Lewandowski, Zbigniew; Abrahamson, Michael T.
A 2-dimensional model has been developed which couples hydrodynamics, solute transport and reaction in a steady state biofilm system of irregular geometry under laminar flow. Biofilm thickness is initially specified over the domain and remains constant during the simulations. The Navier-Stokes equations are coupled with advection-diffusion-reaction equations describing oxygen transport and solved using finite differences. This model facilitates computational investigation of fluid velocity and solute concentration distributions in proximity to the fluid-biofilm interface. Model evaluation has been carried out using dissolved oxygen profiles measured by microsensors in a rectangular open channel with a 300 μm (approximate) artificial biofilm composed of alginate gel with an 8×1010 cells/ml concentration of Ps. aeruginosa cells. Significant variability in dissolved oxygen profile shape was observed at three locations on the artificial biofilm. Model simulations of these experiments facilitated a direct comparison between observed and computed values of dissolved oxygen concentration in the vicinity of the fluid-biofilm interface. Simulated profiles agreed closely with measured profiles at all three locations.