Center for Biofilm Engineering (CBE)
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At the Center for Biofilm Engineering (CBE), multidisciplinary research teams develop beneficial uses for microbial biofilms and find solutions to industrially relevant biofilm problems. The CBE was established at Montana State University, Bozeman, in 1990 as a National Science Foundation Engineering Research Center. As part of the MSU College of Engineering, the CBE gives students a chance to get a head start on their careers by working on research teams led by world-recognized leaders in the biofilm field.
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Item The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface(1999) Jordan, Ryan N.; Nichols, E. P.; Cunningham, Alfred B.Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.Item Mobilization of a broad host range plasmid from pseudomonas putida to an established biofilm of bacillus azotoformans part ii: modeling(1998-02) Beaudoin, D. L.; Bryers, James D.; Cunningham, Alfred B.; Peretti, Steven W.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.Item Mobilization of a broad host range plasmid from pseudomonas putida to an established biofilm of bacillus azotoformans part i: experiments(1998-02) Beaudoin, D. L.; Bryers, James D.; Cunningham, Alfred B.; Peretti, Steven W.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.Item The effect of bacterial injury on toluene degradation and respiration rates in vapor phase bioreactors(1997) Jones, Warren L.; Mirpuri, Rajesh G.; Lewandowski, Zbigniew; Cunningham, Alfred B.The effects of prolonged toluene exposure and degradation on bacterial cultures of Pseudomonas putida 54G were investigated in three reactor systems: a batch suspended culture system, a bench-scale flat plate biofilm reactor, and a bench-scale packed column reactor. Humidified air containing 150 ppmv (toluene limiting) to 750 ppmv (oxygen limiting) toluene vapor was the sole source of carbon and energy supplied to these systems. Results from the suspended batch culture experiments were used to develop rate expressions and kinetic parameters for loss of culturability and of toluene degradative capacity. Experiments in the flat plate reactor were carried out to examine the effects of injury on biofilm structure and function. The packed column studies were performed under conditions relevant to field application, and confirmed results from the other two studies - that decreased culturability on toluene media correlated with decreased specific toluene degradation rate, particularly at higher toluene concentration.Item Predictive model for toluene degradation and microbial phenotypic profiles in flat plate vapor phase bioreactor(1997-06) Mirpuri, Rajesh G.; Sharp, Robert R.; Lewandowski, Zbigniew; Cunningham, Alfred B.A predictive model has been developed to describe degradation of toluene in a flat-plate vapor phase bioreactor (VPBR). The VPBR model incorporates kinetic, stoichiometric, injury, and irreversible loss coefficients from suspended culture studies for toluene degradation by P. putida 54G and measured values of Henry's law constant and boundary layer thickness at the gas-liquid and liquid-biofilm interface. The model is used to estimate the performance of the reactor with respect to toluene degradation and to predict profiles of toluene concentration and bacterial physiological state within the biofilm. These results have been compared with experimentally determined values from a flat plate VPBR under electron acceptor and electron donor limiting conditions. The model accurately predicts toluene concentrations in the vapor phase and toluene degradation rate by adjusting only three parameters: biomass density and rates of death and endogenous decay. Qualitatively, the model also predicts gradients in the physiological state cells in the biofilm. This model provides a rational design for predicting an upper limit of toluene degradation capability in a VPBR and is currently being tested to assess applications for predicting performance of bench and pilot-scale column reactors.Item 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.Item Bench-scale/field-scale interpretations: an overview(1995) Cunningham, Alfred B.Item Modeling biofilm accumulation and mass transport in a porous medium under high substrate loading(1995-09) Wanner, O.; Cunningham, Alfred B.; Lundman, Ross WadeA packed bed biofilm reactor inoculated with pure culture Pseudomonas aeruginosa was run under high substrate loading and constant flow rate conditions. The 3.1-cm-diameter cylindrical reactor was 5 cm in length and packed with 1-mm glass beads. Daily observations of biofilm thickness, influent and effluent glucose substrate concentration, and effluent dissolved and total organic carbon were made during the 13-day experiment. Biofilm thickness appeared to rech quasi-steady-state condition after 10 days. A published biofilm process simulation program (AQUASIM) was used to analyze experimental data. Comparison of observed and simulated variables revealed three distinct phases of biofilm accumulation during the experiment: an initial phase, a growth phase, and a mature biofilm phase. Different combinations of biofilm and mass transport process variables were found to be important during each phase. Biofilm detachment was highly correlated with shear at the biofilm surface during all three phases of biofilm development.Item Scale-up implications of respirometrically determined microbial kinetics parameters(1994) Sturman, Paul J.; Sharp, Robert R.; DeBar, J. B.; Stewart, Philip S.; Cunningham, Alfred B.; Wolfram, James H.Item Degradation of xenobiotic compounds in situ: capabilities and limits(1994-10) Bouwer, Edward J.; Durant, N.; Wilson, L.; Zhang, Weiyan; Cunningham, Alfred B.Exploiting microorganisms for remediation of waste sites is a promising alternative to groundwater pumping and above ground treatment. The objective of in situ bioremediation is to stimulate the growth of indigenous or introduced microorganisms in regions of subsurface contamination, and thus to provide direct contact between microorganisms and the dissolved and sorbed contaminants for biotransformation. Subsurface microorganisms detected at a former manufactured gas plant site contaminated with coal tars mineralized significant amounts of naphthalene (8–43%) and phenanthrene (3–31%) in sediment-water microcosms incubated for 4 weeks under aerobic conditions. Evidence was obtained for naphthalene mineralization (8–13%) in the absence of oxygen in field samples. These data suggest that biodegradation of these compounds is occurring at the site, and the prospects are good for enhancing this biodegradation. Additional batch studies demonstrated that sorption of naphthalene onto aquifer materials reduced the extent and rate of biodegradation, indicating that desorption rate was controlling the biodegradation performance.