Polysaccharides and bacterial plugging. [Quarterly report], April 1--June 30, 1991

This research seeks to model bacterial transport in porous media, to determine the importance of polysaccharides bridging as a retentive mechanism, and to identify key parameters that influence porous media plugging. Task 1 of the project is the determination of the grown kinetics of the Leuconostoc bacteria and how they are affected by the nutrient feed and surface effects. Task 2 will quantify the importance of polysaccharide production as a cell retention mechanism; and Task 3 is the elucidation of the rate of polysaccharide production and the combined effect that polysaccharide production and cell growth has upon plugging. Verification of the two parameter model, as presented in the past quarterly reports, was the focus of batch experiments. Three series of batch culture experiments, were conducted with varying yeast extract concentrations and with no saccharides. The specific rate constants for the cells of new inoculum are higher than the rates found from the past experiments using cultured cells as inoculum. This indicates that the cells used in the original experiments have undergone a phenotypic alteration. Thus, the model developed could not be verified and requires additional data. In future experiments, the growth of the inoculum will be controlled by minimizing the number of cell transfers before use in kinetic experiments. Two additional experimental series have been completed to determine the rate of cellular production of dextran. The first set of experiments consisted of two batch reactors containing 5 and 36 g/L of sucrose and 10 g/L of yeast extract in each