Date of Award


Degree Type


Degree Name

Master of Science


Chemical Engineering

Major Professor

Paul D. Frymier

Committee Members

Paul Bienkowski, Steven Ripp


Methods of developing and improving toxicity assays using genetically engineered bioluminescent bacteria PM6 and Shk1 were investigated. The EC50 values for three metals (zinc, copper, and lead) were determined using these two strains and were compared with the EC50 values calculated from the Microtox® assay, published inhibition to activated sludge specific oxygen uptake rate (SOUR) data (Madonii et al., 1999), and published EC50 values from Microtox® for the same compounds (Kaiser and Devillers, 1994). This was done to evaluate the effectiveness of using strains PM6 and Shk1 to predict toxic effects to activated sludge as indicated by respiration inhibition. A number of factors affecting toxicity assays were examined including temperature control, cell storage method (lyophilization and storage temperature), activation time, and mixing prior to luminescence measurement.

A toxicity testing protocol developed by Lajoie et al. (2002) was used and adapted to this study. Based on the results of these experiments, it was concluded that toxicity assays using PM6 and Shk1 provide EC50 values closer to respiration inhibition EC50 values than Microtox®.

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