A pure culture of Pseudomonas aeruginosa ( ATCC 10145 ) was used for the biodegradation of phenol and benzoic acid. Two sets of small scale (shaker flask) experiments were originally performed: in the first set, phenol was the only carbon source present while in the second, benzoic acid was the sole carbon source. These experiments revealed the kinetics of benzoic acid degradation (they were found to be described by a Monod, non-inhibitory model), as well as of phenol biodegradation (they were found to be described by Andrews\u27inhibitory model) by Pseudomonas aeruginosa.
The kinetic expressions from the small scale experiments were used in predicting biodegradation in a larger scale. For the case of benzoic acid, batch as well as sequencing batch operation of a 4-liter reactor showed very good agreement between experimental data and model predictions. The ultimate objective was to study biodegradation of mixtures of phenol and benzoic acid, and to predict it from the kinetic expressions derived as described above. Assuming simultaneous, non preferential biodegradation of the two substrates, a model was derived for both batch and sequencing batch reactor operation. Unfortunately, the model did not fit the data under these assumptions. Batch data showed a clear preference of Pseudomonas under these assumptions. Batch data showed a clear preference of Pseudomonas aeruginosa for benzoic acid (diauxie phenomenon), and the two substrates were completely but sequentially mineralized. In SBR operation, the two substrates were simultaneously used but the model could not describe the data. It is assumed that in continuous operation the substrates are simultaneously used, but again, there is a certain preference for benzoic acid
