Phenol biodegradation by the strain Pseudomonas putida affected by constant electric field

Phenol and its derivatives are some of the most dangerous organic pollutants released into the environment. Various methods, including microbial processes, have been applied to reduce their concentrations to acceptable values in the waste streams. The present study considers the effect of constant electric field on the phenol biodegradation potential of the strain Pseudomonas putida in aqueous media. The following significant effects are observed: the constant electric field applied enhances the specific growth rate of the bacteria studied at a specified anode potential, i.e., 0.8 V versus the standard hydrogen electrode, compared to a culture without application of electricity. The amount of destroyed phenol at this anode potential is three times higher than that at the control experiment. The enzyme analyses show that the electric field stimulates the activity of phenol hydroxylase (from 0.095 to 0.281 U/mg protein) and catechol-1,2-dioxylase (from 0.688 to 1.22 U/mg protein) at the same anodic potential. The lack of catechol-2,3-dioxylase activity is an indication for the ortho-oxidative pathway for phenol biodegradation in the case under consideration. Comparison of the electric current efficiencies, measured (3.2 mA h) and stoichiometric (2.54 A h) ones shows that the stimulation effect is of biochemical origin, but not due to electrochemical processes on the anode.