Biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel

Batch experiments were carried out to evaluate the biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel pellets in a bubble column bioreactor at different conditions. The bacteria were activated and gradually acclimatized to high concentrations of phenol of up to 300 mg/l. The experimental results indicated that the biodegradation capabilities of P. putida are highly affected by temperature, pH, initial phenol concentration and the abundance of the biomass. The biodegradation rate is optimized at 30 °C, a pH of 7 and phenol concentration of 75 mg/l. Higher phenol concentrations inhibited the biomass and reduced the biodegradation rate. At high phenol concentration, the PVA particle size was found to have negligible effect on the biodegradation rate. However, for low concentrations, the biodegradation rate increased slightly with decreasing particle size. Other contaminants such heavy metals and sulfates showed no effect on the biodegradation process. Modeling of the biodegradation of phenol indicated that the Haldane inhibitory model gave better fit of the experimental data than the Monod model, which ignores the inhibitory effects of phenol.