This paper is a comprehensive review related to the biological degradation of phenol by microorganisms. The aromatic compound, phenol or hydroxybenzene, is produced industrially or naturally. Many microorganisms that are able to biodegrade phenol have been isolated and at the same time, the metabolic pathways responsible for these metabolic processes have been determined. A large number of bacteria were studied in detail especially, pure cultures as well as the pathways of aerobic phenol metabolism and the enzymes involved. Phenol oxygenation occurred as the initial steps through phenol hydroxylase enzymes leading to formation of catechol, pursued by the splitting of the adjacent ring or in between the two groups of catechol hydroxyls. Thus, the physical and chemical environments plus the chemical structures that affecting biodegradation processes are important determining factors for combating of pollution. This nature of chemical structure for the other aromatic compounds is also a main decisive factor of biodegradability.

Phenol is one of the main pollutants that have a serious impact on the environment and can even be very critical to human health. The biodegradation of phenol can be considered an increasingly important pollution control process. In this study, the degradation of phenol by Pseudomonas fredriksbergsis was investigated for the first time under different growth conditions. Six different initial concentrations of phenol were used as the primary substrate. Culture conditions had an important effect on these cells' ability to biodegrade phenol. The best growth of this organism and its highest biodegradation level of phenol were noticed at pH 7, temperature 28 °C, and periods of 36 and 96 h, respectively. The highest biodegradation rate was perceived at 700 mg/L initial phenol concentration. Approximately 90% of the phenol (700 mg/L) was removed in less than 96 hours of incubation time. It was found that the Haldane model best fitted the relationship between the specific growth rate and the initial phenol concentration, whereas the phenol biodegradation profiles time could be adequately described by the modified Gompertz model. The parameters of the Haldane equation are: 0.062 h −1 , 11 ppm, and 121 ppm for Haldane's maximum specific growth rate, the half-saturation coefficient, and the Haldane's growth kinetics inhibition coefficient, respectively. The Haldane equation fitted the experimental data by minimizing the sum of squared error (SSR) to 1.36×10 -3 .