Batch phenol biodegradation study and application of factorial experimental design

Abstract

A bacterium, Pseudomonas aeruginosa (ATTC27853), was investigated for its ability to grow and to degrade phenol as sole carbon source, in aerobic batch culture. The parameters which affect the substrate biodegradation such as the adaptation of bacteria to phenol, the temperature, and the nature of the bacteria were investigated. The results show that for a range of temperature of 30 to 40°C, the best degradation of phenol for a concentration of 100mg/l was observed at 30°C. The regeneration of the bacterium which allows the reactivation of its enzymatic activity, shows that the degradation of 100 mg/ l of substrate at 30° C required approximately 50 hours with revivified bacteria, while it only starts after 72 hours for those no revivified. Adapted to increasing concentrations, allows the bacteria to degrade a substrate concentration of about 400mg/ l in less than 350 hours. A second part was consisted in the determination of a substrate degradation model using the factorial experiment design, as a function of temperature (30-40°C) and of the size of the inoculums (260.88 - 521.76mg/ l). The results were analyzed statistically using the Student’s t-test, analysis of variance, and F-test. The value of R 2 (0.99872) and adjusted R 2 (0.9962) close to 1.0, verifies the good correlation between the observed and the predicted values, and provides the excellent relation ship between the independent variables (factors) and the response (the time of the phenol degradation). F-value found above 200, indicates that the considered model is statistically significant.