Biomedical subjects

Jeanne M VanBriesen

Publications and source records attributed to Jeanne M VanBriesen.

6 recordsLinked to original sources

PubMed2006

Expanded thermodynamic model for microbial true yield prediction.

Thermodynamic methods to predict true yield and stoichiometry of bacterial reactions have been widely used in biotechnology and environmental engineering. However, yield predictions are often inaccurate for certain simple organic compounds. This work evaluates an existing method and identifies the cause of prediction errors for compounds with low degree of reductance of carbon. For these compounds, carbon, not energy or reducing equivalents, constrains growth. Existing thermodynamically-based models do not account for the potential of carbon-limited growth. The improved method described here consists of four balances: carbon balance, nitrogen balance, electron balance, and energy balance. Two efficiency terms, K1 and K2 are defined and estimated from a priori analysis. The results show that K1 and K2 are nearly the same in value so that only one coefficient, K = 0.41 is used in the modified model. Comparisons with observed yields show that use of the new model and parameters results in significantly improved yield estimation based on inclusion of the carbon balance. The average estimation error is less than 6% for the data set presented.

Bacteria↗

PubMed2005

Raman spectroscopy and chemical imaging for quantification of filtered waterborne bacteria.

Rapid and reliable assessment of pathogenic microbial contamination in water is critically important. In the present work we evaluated the suitability of Raman Spectroscopy and Chemical Imaging as enumeration techniques for waterborne pathogens. The prominent C-H stretching band observed between 2800-3000 cm(-1) of the spectrum is used for quantification purposes. This band provides the highest intensity of the bacterial-spectrum bands facilitating the detection of low number of microorganisms. The intensity of the Raman response correlates with number of cells present in drops of sample water on aluminum-coated slides. However, concentration of pathogens in drinking and recreational water is low, requiring a concentration step, i.e., filtering. Subsequent evaluation of filtering approaches for water sampling for Raman detection showed significant background signal from alumina and silver membranes that reduces method sensitivity. Samples concentrated by filtration show good correlation between Raman spectroscopy and other quantification methods including turbidity (R(2)=0.92), plate counts (R(2)=0.87) and dry weight (R(2)=0.97). Background interferences did not allow for evaluation of this relationship at low cell concentrations.

Aluminum↗

PubMed2004

Statistical method to evaluate the occurrence of PCB transformations in river sediments with application to Hudson River data.

Polychlorinated biphenyls (PCBs) were produced in the mid 1900s for industrial use. The term PCBs refers to 209 theoretically possible chlorinated compounds of the biphenyl molecule (congeners). The number and location of the chlorines govern both the environmental fate and toxicity of each congener. Changes in the distribution of congeners in river sediments can result from congener transformation and/or preferential congener transport. This study exploits the distribution of PCB congeners, specifically congeners that maintain a constant ratio relationship in the commercially manufactured PCB mixtures (Aroclors), to quantify the likelihood of congener distribution shifts in river sediment. By using relative abundances, the influence of total PCB bias is eliminated. Correlated congeners (tracker pairs) maintain a constant relative proportion in sequentially more-highly chlorinated Aroclors, thus there is no need to know the source contaminating Aroclors a priori. Using the Frame et al. database of Aroclor congener distributions, 276 pairs of correlated congeners, constructed from 95 individual congeners, are identified. A comparison study of Aroclors and Hudson River sediments included 218 of the 276 tracker pairs. Conclusive evidence of a shift in the congener proportions is found in 120 of the 218 cases, a much greater number than expected if no change in congener distribution had occurred.

Databases, Factual↗

PubMed2002

Yield prediction and stoichiometry of multi-step biodegradation reactions involving oxygenation.

Microorganisms can initiate the degradation of organic compounds by oxygenation reactions that require the investment of energy and electrons. This diversion of energy and electrons away from synthesis reactions leads to decreased overall cell yields. A thermodynamic method was developed that improves the accuracy of cell yield prediction for compounds degraded through pathways involving oxygenation reactions. This method predicts yields and stoichiometry for each step in the biodegradation pathway, thus enabling modeling a multi-step biodegradation process in which oxygenations occur and intermediates may persist. EDTA and benzene biodegradation are presented as examples. The method compares favorably with other yield prediction methods while providing additional information of yields for intermediates produced in the degradation pathway.

Benzene↗

PubMed2002

Evaluation of methods to predict bacterial yield using thermodynamics.

Thermodynamic models can be used to predict bacterial yields and develop stoichiometric representation of biological reactions in the absence of empirical data. Several methods have been used by microbiologists, biotechnologists, and environmental engineers. This manuscript illustrates that these formulations are related. Yields predicted by estimation of Gibbs energy of dissipation and yields predicted by assumed efficiency of energy capture are comparable. Direct comparison of yield predictions from different methods shows the effects of assumptions inherent in the methodologies. Mathematical relationships between estimated values from the different methods help identify the best predictions from each method to bound the estimate of bacterial yield.

Algorithms↗

PubMed2002

Mathematical modeling of precipitation and dissolution reactions in microbiological systems.

We expand the biogeochemical model CCBATCH to include a precipitation/dissolution sub-model that contains kinetic and equilibrium options. This advancement extends CCBATCH's usefulness to situations in which microbial reactions cause or are affected by formation or dissolution of a solid phase. The kinetic option employs a rate expression that explicitly includes the intrinsic kinetics for reaction or mass-transport control, the difference from thermodynamic equilibrium, and the aqueous concentration of the rate-limiting metal or ligand. The equilibrium feature can be used alone, and it also serves as check that the kinetic rate never is too fast and "overshoots" equilibrium. The features of the expanded CCBATCH are illustrated by an example in which the precipitation of Fe(OH)3(s) allows the biodegradation of citric acid, even though complexes are strong and not bioavailable. Precipitation releases citrate ligand, and biodegradation of the citrate increases the pH.

Algorithms↗