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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A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core
(2017-05) D'Andrilli, Juliana; Foreman, Christine M.; Sigl, Michael; Priscu, John C.; McConnell, Joseph R.
Englacial ice contains a significant reservoir of organic material (OM), preserving a chronological record of materials from Earth's past. Here, we investigate if OM composition surveys in ice core research can provide paleoecological information on the dynamic nature of our Earth through time. Temporal trends in OM composition from the early Holocene extending back to the Last Glacial Maximum (LGM) of the West Antarctic Ice Sheet Divide (WD) ice core were measured by fluorescence spectroscopy. Multivariate parallel factor (PARAFAC) analysis is widely used to isolate the chemical components that best describe the observed variation across three-dimensional fluorescence spectroscopy (excitation–emission matrices; EEMs) assays. Fluorescent OM markers identified by PARAFAC modeling of the EEMs from the LGM (27.0–18.0 kyr BP; before present 1950) through the last deglaciation (LD; 18.0–11.5 kyr BP), to the mid-Holocene (11.5–6.0 kyr BP) provided evidence of different types of fluorescent OM composition and origin in the WD ice core over 21.0 kyr. Low excitation–emission wavelength fluorescent PARAFAC component one (C1), associated with chemical species similar to simple lignin phenols was the greatest contributor throughout the ice core, suggesting a strong signature of terrestrial OM in all climate periods. The component two (C2) OM marker, encompassed distinct variability in the ice core describing chemical species similar to tannin- and phenylalanine-like material. Component three (C3), associated with humic-like terrestrial material further resistant to biodegradation, was only characteristic of the Holocene, suggesting that more complex organic polymers such as lignins or tannins may be an ecological marker of warmer climates. We suggest that fluorescent OM markers observed during the LGM were the result of greater continental dust loading of lignin precursor (monolignol) material in a drier climate, with lower marine influences when sea ice extent was higher and continents had more expansive tundra cover. As the climate warmed, the record of OM markers in the WD ice core changed, reflecting shifts in carbon productivity as a result of global ecosystem response..
A 3D computer model analysis of three hypothetical biofilm detachment mechanisms
(2007-08) Chambless, Jason D.; Stewart, Philip S.
Three hypothetical mechanisms of detachment were incorporated into a three-dimensional computer model of biofilm development. The model integrated processes of substrate utilization, substrate diffusion, growth, cell advection, and detachment in a cellular automata framework. The purpose of this investigation was to characterize each of the mechanisms with respect to four criteria: the resulting biofilm structure, the existence of a steady state, the propensity for sloughing events, and the dynamics during starvation. The three detachment mechanisms analyzed represented various physical and biological influences hypothesized to affect biofilm detachment. The first invoked the concept of fluid shear removing biomass that protrudes far above the surface and is therefore subjected to relatively large drag forces. The second pathway linked detachment to changes in the local availability of a nutrient. The third pathway simulated an erosive process in which individual cells are lost from the surface of a biofilm cell cluster. The detachment mechanisms demonstrated diverse behaviors with respect to the four analysis criteria. The height dependant mechanism produced flat, steady state biofilms that lacked sloughing events. Detachment based on substrate limitation produced significant sloughing events. The resulting biofilm structures included distinct, hollow clusters separated by channels. The erosion mechanism produced neither a non-zero steady state nor sloughing events. A mechanism combining all three detachment mechanisms produced mushroom-like structures. The dynamics of biofilm decay during starvation were distinct for each detachment mechanism. These results show that detachment is a critical determinant of biofilm structure and of the dynamics of biofilm accumulation and loss.
A 3D model of antimicrobial action on biofilms
(2005) Hunt, Stephen Michael; Hamilton, Martin A.; Stewart, Philip S.
A three-dimensional cellular automata model of biofilm dynamics was adapted to simulate the protection from killing by antimicrobial agents afforded to microorganisms in the biofilm state. The model incorporated diffusion and simultaneous utilization of a single substrate, growth and displacement of cells, detachment, and killing by an antimicrobial agent. The rate of killing was assumed to be directly proportional to the local concentration of substrate available to the microorganisms. Some of the features predicted by this model included development of dynamic, heterogeneous biofilm structures, gradients in substrate concentration leading to regions of substrate depletion in the interior of large cell clusters, variable killing by an antimicrobial agent from one simulation to the next, greater killing of cells at the periphery of cell clusters compared to those cells which were more deeply embedded, and reduced overall antimicrobial susceptibility of cells in the biofilm. These simulations show that substrate limitation can contribute to the protection from antimicrobial agents in biofilms but cannot explain the long-term persistence of biofilm viability that is often observed in practice.
Abandoned well CO2 leakage mitigation using biologically induced mineralization: Current progress and future directions
(2013-02) Cunningham, Alfred B.
Methods of mitigating leakage or re-plugging abandoned wells before exposure to CO2are of high potential interest to prevent leakage of CO2 injected for geologic carbon sequestration in depleted oil and gas reservoirs where large numbers of abandoned wells are often present. While CO2resistant cements and ultrafine cements are being developed, technologies that can be delivered via low viscosity fluids could have significant advantages including the ability to plug small aperture leaks such as fractures or delamination interfaces. Additionally there is the potential to plug rock formation pore space around the wellbore in particularly problematic situations. We are carrying out research on the use of microbial biofilms capable of inducing the precipitation of crystalline calcium carbonate using the process of ureolysis. This method has the potential to reduce well bore permeability, coat cement to reduce CO2â€“related corrosion, and lower the risk of unwanted upward CO2 migration. In this spotlight, we highlight research currently underway at the Center for Biofilm Engineering (CBE) at Montana State University (MSU) in the area of ureolytic biomineralization sealing for reducing CO2 leakage risk. This research program combines two novel core testing systems and a 3-dimensional simulation model to investigate biomineralization under both radial and axial flow conditions and at temperatures and pressures which permit CO2 to exist in the supercritical state.This combination of modeling and experimentation is ultimately aimed at developing and verifying biomineralization sealing technologies and strategies which can successfully be applied at the field scale for carbon capture and geological storage (CCGS) projects.
Accelerated Gibbs sampling of normal distributions using matrix splittings and polynomials
(2017-11) Fox, Colin; Parker, Albert E.
Standard Gibbs sampling applied to a multivariate normal distribution with a specified precision matrix is equivalent in fundamental ways to the Gauss-Seidel iterative solution of linear equations in the precision matrix. Specifically, the iteration operators, the conditions under which convergence occurs, and geometric convergence factors (and rates) are identical. These results hold for arbitrary matrix splittings from classical iterative methods in numerical linear algebra giving easy access to mature results in that field, including existing convergence results for antithetic-variable Gibbs sampling, REGS sampling, and generalizations. Hence, efficient deterministic stationary relaxation schemes lead to efficient generalizations of Gibbs sampling. The technique of polynomial acceleration that significantly improves the convergence rate of an iterative solver derived from a symmetric matrix splitting may be applied to accelerate the equivalent generalized Gibbs sampler. Identicality of error polynomials guarantees convergence of the inhomogeneous Markov chain, while equality of convergence factors ensures that the optimal solver leads to the optimal sampler. Numerical examples are presented, including a Chebyshev accelerated SSOR Gibbs sampler applied to a stylized demonstration of low-level Bayesian image reconstruction in a large 3-dimensional linear inverse problem.
Accumulation of a biofilm of k. pneumoniae and p. aeruginosa
(1989-12) Siebel, M. A.; Characklis, William G.
The accuracy of oxygen flux measurements using microelectrodes
(1998-12) Rasmussen, Kjetil; Lewandowski, Zbigniew
An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a flat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the oxygen profiles above and within the graphite felt. From the shape of the oxygen profile we evaluated the oxygen flux to the graphite felt. This provided us with two sets of data, the true oxygen flux, calculated from polarization current, and the oxygen flux estimated from microelectrode measurements. Comparing these two fluxes, for different flow velocities, showed that the fluxes evaluated from the polarization current were different from those evaluated from the oxygen profiles. The differences were likely caused by the presence of the microelectrode in the mass boundary layer and/or by the simplifying assumptions accepted in computational procedures employed to calculate oxygen fluxes. For low flow velocities, between zero and 1.0 cm s−1, the differences were velocity sensitive; the higher the flow velocity, the bigger the difference. For higher flow velocities, between 1 cm s−1 and 3 cm s−1, the flux of oxygen estimated from the microelectrode measurements was consistently approximately 80% higher than the true oxygen flux estimated from the polarization current.
Actin recruitment to the Chlamydia inclusion is spatiotemporally regulated by a mechanism that requires host and bacterial factors
(2012-10) Chin, E.; Kirker, Kelly R.; Zuck, Meghan; James, Garth A.; Hybiske, K.
The ability to exit host cells at the end of their developmental growth is a critical step for the intracellular bacterium Chlamydia. One exit strategy, extrusion, is mediated by host signaling pathways involved with actin polymerization. Here, we show that actin is recruited to the chlamydial inclusion as a late event, occurring after 20 hours post-infection (hpi) and only within a subpopulation of cells. This event increases significantly in prevalence and extent from 20 to 68 hpi, and actin coats strongly correlated with extrusions. In contrast to what has been reported for other intracellular pathogens, actin nucleation on Chlamydia inclusions did not â€˜flashâ€™, but rather exhibited moderate depolymerization dynamics. By using small molecule agents to selectively disrupt host signaling pathways involved with actin nucleation, modulate actin polymerization dynamics and also to disable the synthesis and secretion of chlamydial proteins, we further show that host and bacterial proteins are required for actin coat formation. Transient disruption of either host or bacterial signaling pathways resulted in rapid loss of coats in all infected cells and a reduction in extrusion formation. Inhibition of Chlamydia type III secretion also resulted in rapid loss of actin association on inclusions, thus implicating chlamydial effector proteins(s) as being central factors for engaging with host actin nucleating factors, such as formins. In conclusion, our data illuminate the host and bacterial driven process by which a dense actin matrix is dynamically nucleated and maintained on the Chlamydia inclusion. This late stage event is not ubiquitous for all infected cells in a population, and escalates in prevalence and extent throughout the developmental cycle of Chlamydia, culminating with their exit from the host cell by extrusion. The initiation of actin recruitment by Chlamydia appears to be novel, and may serve as an upstream determinant of the extrusion mechanism
Action of antimicrobial substances produced by different oil reservoir Bacillus strains against biofilm formation
(2008-03) Korenblum, E.; Sebastián, G. V.; Paiva, M. M.; Coutinho, C. M. L. M.; Magalhães, F. C. M.; Peyton, Brent M.; Seldin, L.
Microbial colonization of petroleum industry systems takes place through the formation of biofilms, and can result in biodeterioration of the metal surfaces. In a previous study, two oil reservoir Bacillus strains (Bacillus licheniformis T6-5 and Bacillus firmus H2O-1) were shown to produce antimicrobial substances (AMS) active against different Bacillus strains and a consortium of sulfate-reducing bacteria (SRB) on solid medium. However, neither their ability to form biofilms nor the effect of the AMS on biofilm formation was adequately addressed. Therefore, here, we report that three Bacillus strains (Bacillus pumilus LF4-used as an indicator strain, B. licheniformis T6-5, and B. firmus H2O-1, and an oil reservoir SRB consortium (T6lab) were grown as biofilms on glass surfaces. The AMS produced by strains T6-5 and H2O-1 prevented the formation of B. pumilus LF4 biofilm and also eliminated pre-established LF4 biofilm. In addition, the presence of AMS produced by H2O-1 reduced the viability and attachment of the SRB consortium biofilm by an order of magnitude. Our results suggest that the AMS produced by Bacillus strains T6-5 and H2O-1 may have a potential for pipeline-cleaning technologies to inhibit biofilm formation and consequently reduce biocorrosion.
Action of chlorhexidine digluconate against yeast and filamentous forms in an early-stage candida albicans biofilm
(2002-11) Suci, Peter A.; Tyler, Bonnie J.
An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded into the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t-test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.
Action of glutaraldehyde and nitrite against sulfate-reducing bacterial biofilms
(2002-12) Gardner, Lawrence Robert; Stewart, Philip S.
A continuous flow reactor system was developed to evaluate the efficacy of antimicrobial treatments against sulfate-reducing bacterial biofilms. An annular reactor operating at a nominal dilution rate of 0.5 h-1 was fed one-tenth strength Postgate C medium diluted in 1.5% NaCl and was inoculated with a mixed culture enriched from oilfield-produced water on the same medium. Thin biofilms developed in this reactor after 2 days of operation. The activity of these biofilms resulted in approximately 50 mg S l-1 of sulfide at steady state prior to biocide treatment. Biocide efficacy was quantified by recording the time required for sulfide production to recover following an antimicrobial treatment. In a control experiment in which pure water was applied, the time required to reach 10 mg S l-1 sulfide after the treatment was 1.7±1.2 h, whereas the time to reach this level of sulfide after a pulse dose of 500 mg l-1 glutaraldehyde was delayed to 61±11 h. Nitrite treatment suppressed sulfide production as long as the nitrite concentration remained above 15 mg N l-1. Sulfide production recovered more rapidly after nitrite treatment than it did after glutaraldehyde treatment. Gardner, L.R., P.S. Stewart, "Action of Glutaraldehyde and Nitrite Against Sulfate-Reducing Bacterial Biofilms," J. Industrial Microbiol. Biotech. 29(6):354 (2002).
Activity and stability of a recombinant plasmid-borne tce degradative pathway in biofilm cultures
(1998-08) Sharp, Robert R.; Bryers, James D.; Jones, Wallace E.
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.
Activity and stability of a recombinant plasmid-borne tce degradative pathway in suspended cultures
(1998-02) Sharp, Robert R.; Bryers, James D.; Jones, Warren G.; Shields, Malcom S.
The retention and expression of the plasmid-borne, TCE degradative toluene-ortho-monooxygenase (TOM) pathway in suspended continuous cultures of transconjugant Burkholderia cepacia 17616 (TOM31c) were studied. Acetate growth and TCE degradation kinetics for the transconjugant host are described and utilized in a plasmid loss model. Plasmid maintenance did not have a significant effect on the growth rate of the transconjugant. Both plasmid-bearing and plasmid-free strains followed Andrews inhibition growth kinetics when grown on acetate and had maximum growth rates of 0.22 h−1. The transconjugant was capable of degrading TCE at a maximum rate of 9.7 nmol TCE/min · mg protein, which is comparable to the rates found for the original plasmid host, Burkholderia cepacia PR131 (TOM31c). The specific activity of the TOM pathway was found to be a linear function of growth rate. Plasmid maintenance was studied at three different growth rates: 0.17/h, 0.1/h, and 0.065/h. Plasmid maintenance was found to be a function of growth rate, with the probability of loss ranging from 0.027 at a growth rate of 0.065/h to 0.034 at a growth rate 0.17/h. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 287–296, 1998.
Activity of pseudomonas aeruginosa in biofilms: effect of calcium
(1989-01) Turakhia, Mukesh Harilal; Characklis, William G.
Aerobic glucose metabolism by Pseudomonas aeruginosa biofilms at various calcium loading rates was investigated. The influence of calcium on specific growth rate, extracellular polymeric substance (EPS) formation rate, biofilm detachment rate, and biofilm calcium concentrations was determined. Calcium accumulated in the biofilm in proportion to the liquid phase concentration. Increasing calcium concentration increased the cohesiveness of the biofilm as indicated by a lower relative detachment rate. Specific activity in the biofilm was the same as that measured in a chemostat and was not influenced by changing calcium concentration. EPS formation rate in the biofilm was unaffected by calcium concentration but was higher than that observed in a chemostat.
Activity of Pseudomonas aeruginosa in Biofilms: Steady State
(1984-12) Bakke, Rune; Trulear, Michael Gerald; Robinson, J. A.; Characklis, William G.
Aerobic glucose metabolism by Pseudomonas aeruginosa in steady-state biofilms at various substrate loading rates and reactor dilution rates was investigated. Variables monitored were substrate (glucose), biofilm cellular density, biofilm extracellular polymeric substance (EPS) density, and suspended cellular and EPS concentrations. A mathematical model developed to describe the system was compared to experimental data. Intrinsic yield and rate coefficients included in the model were obtained from suspended continuous culture studies of glucose metabolism by P. aeruginosa. Experimental data compared well with the mathematical model, suggesting that P. aeruginosa does not behave differently in steady-state biofilm cultures, where diffusional resistance is negligible, than in suspended cultures. This implies that kinetic and stoichiometric coefficients for P. aeruginosa derived in suspended continuous culture can be used to describe steady-state biofilm processes.
Activity-based cell sorting reveals responses of uncultured archaea and bacteria to substrate amendment
(Springer Science and Business Media LLC, 2020) Reichart, Nicholas J.; Jay, Zachary J.; Krukenberg, Viola; Parker, Albert E.; Lange Spietz, Rachel K.; Hatzenpichler, Roland
Metagenomic studies have revolutionized our understanding of the metabolic potential of uncultured microorganisms in various ecosystems. However, many of these genomic predictions have yet to be experimentally tested, and the functional expression of genomic potential often remains unaddressed. In order to obtain a more thorough understanding of cell physiology, novel techniques capable of testing microbial metabolism under close to in situ conditions must be developed. Here, we provide a benchmark study to demonstrate that bioorthogonal non-canonical amino acid tagging (BONCAT) in combination with fluorescence-activated cell sorting (FACS) and 16S rRNA gene sequencing can be used to identify anabolically active members of a microbial community incubated in the presence of various growth substrates or under changing physicochemical conditions. We applied this approach to a hot spring sediment microbiome from Yellowstone National Park (Wyoming, USA) and identified several microbes that changed their activity levels in response to substrate addition, including uncultured members of the phyla Thaumarchaeota, Acidobacteria, and Fervidibacteria. Because shifts in activity in response to substrate amendment or headspace changes are indicative of microbial preferences for particular growth conditions, results from this and future BONCAT-FACS studies could inform the development of cultivation media to specifically enrich uncultured microbes. Most importantly, BONCAT-FACS is capable of providing information on the physiology of uncultured organisms at as close to in situ conditions as experimentally possible.
Activity-based, genome-resolved metagenomics uncovers key populations and pathways involved in subsurface conversions of coal to methane
(Springer Science and Business Media LLC, 2021-10) McKay, Luke J.; Smith, Heidi J.; Barnhart, Elliott P.; Schweitzer, Hannah D.; Malmstrom, Rex R.; Goudeau, Danielle; Fields, Matthew W.
Microbial metabolisms and interactions that facilitate subsurface conversions of recalcitrant carbon to methane are poorly understood. We deployed an in situ enrichment device in a subsurface coal seam in the Powder River Basin (PRB), USA, and used BONCAT-FACS-Metagenomics to identify translationally active populations involved in methane generation from a variety of coal-derived aromatic hydrocarbons. From the active fraction, high-quality metagenome-assembled genomes (MAGs) were recovered for the acetoclastic methanogen, Methanothrix paradoxum, and a novel member of the Chlorobi with the potential to generate acetate via the Pta-Ack pathway. Members of the Bacteroides and Geobacter also encoded Pta-Ack and together, all four populations had the putative ability to degrade ethylbenzene, phenylphosphate, phenylethanol, toluene, xylene, and phenol. Metabolic reconstructions, gene analyses, and environmental parameters also indicated that redox fluctuations likely promote facultative energy metabolisms in the coal seam. The active "Chlorobi PRB" MAG encoded enzymes for fermentation, nitrate reduction, and multiple oxygenases with varying binding affinities for oxygen. "M. paradoxum PRB" encoded an extradiol dioxygenase for aerobic phenylacetate degradation, which was also present in previously published Methanothrix genomes. These observations outline underlying processes for bio-methane from subbituminous coal by translationally active populations and demonstrate activity-based metagenomics as a powerful strategy in next generation physiology to understand ecologically relevant microbial populations.
Acute septic arthritis
(2002-10) Shirtliff, Mark E.; Mader, Jon T.
Acute septic arthritis may develop as a result of hematogenous seeding, direct introduction, or extension from a contiguous focus of infection. The pathogenesis of acute septic arthritis is multifactorial and depends on the interaction of the host immune response and the adherence factors, toxins, and immunoavoidance strategies of the invading pathogen. Neisseria gonorrhoeae and Staphylococcus aureus are used in discussing the host-pathogen interaction in the pathogenesis of acute septic arthritis. While diagnosis rests on isolation of the bacterial species from synovial fluid samples, patient history, clinical presentation, laboratory findings, and imaging studies are also important. Acute nongonococcal septic arthritis is a medical emergency that can lead to significant morbidity and mortality. Therefore, prompt recognition, rapid and aggressive antimicrobial therapy, and surgical treatment are critical to ensuring a good prognosis. Even with prompt diagnosis and treatment, high mortality and morbidity rates still occur. In contrast, gonococcal arthritis is often successfully treated with antimicrobial therapy alone and demonstrates a very low rate of complications and an excellent prognosis for full return of normal joint function. In the case of prosthetic joint infections, the hardware must be eventually removed by a two-stage revision in order to cure the infection.
Adaptive responses to antimicrobial agents in biofilms
(2005-08) Szomolay, Barbara; Klapper, Isaac; Dockery, Jack D.; Stewart, Philip S.
Bacterial biofilms demonstrate adaptive resistance in response to antimicrobial stress more effectively than corresponding planktonic populations. We propose here that, in biofilms, reaction-diffusion limited penetration may result in only low levels of antimicrobial exposure to deeper regions of the biofilm. Sheltered cells are then able to enter an adapted resistant state if the local time scale for adaptation is faster than that for disinfection. This mechanism is not available to a planktonic population. A mathematical model is presented to illustrate. Results indicate that, for a sufficiently thick biofilm, cells in the biofilm implement adaptive responses more effectively than do freely suspended cells. Effective disinfection requires applied biocide concentration that increases quadratically or exponentially with biofilm thickness.
Addition of copper-sequestering agents to alginate gel to enhance copper recovery from aqueous media
(1995-11) Jang, Larry K.; Nguyen, Duy V.; Kolostyak, K.; Geesey, Gill G.
A mixture of sodium alginate and sodium polystyrenesulfonate (NaPSS) was used as the absorbent for copper in this work. A viscous solution of the mixture was dispensed into a copper-containing solution circulating in a loop fluidized bed reactor to form alginate gel in situ. Batch absorption data was treated by Langmuir model to yield copper binding capacity and binding stability constant. Results were compared with those of our previous work in which no NaPSS was added to Na-alginate. Based on the Langmuir parameters, the critical copper concentration above which the addition of NaPSS can enhance the copper loading of the alginate gel was calculated. The ratio of copper loading of the alginate gel with the addition of NaPSS to that without the addition of NaPSS at any copper concentration was predicted as well. Similar calculations were made for the case of using the mixture of Na-alginate and Microcystis as the copper absorbent.