Kinetics of phenol degradation by selected bacterial strains with different genetic properties

Abstract

The major environmental problem in the northeastern Estonia is the semi-coke mounds in oilshale industry areas, Alternatives to the chemical methods (sorption, ozonation) for removingxenobiotic compounds from leachate are biological methods, like bioaugmentation, where theproperly selected microorganisms are used. Determination of the kinetic constants (maximumspecific growth rates (µmax), lag times (A.), half saturation constants (Kso for oxygenatingactivity and Ksa for growth) and inhibition constants (Ki)) will give us information about therate of pollutant degradation and is the basis for the selection of the most effective bacteria forbioaugmentation. In phenol degradation the initial and rate-limiting enzyme is phenolhydroxylase, encoded by different genes, The aim of this work was to carry out a kineticstudy of the aerobic degradation of phenol using single strains (Pseudomonas mendocinaPC 1, P. fluorescens PC 18, PC20 and PC24) isolated from river water continuously pollutedwith phenolic compounds, The strains PC 1 and PC 18 contain genes for multicomponentphenol hydroxylase, whereas single-component phenol hydroxylase (pheBA operon)characterizes the strains PC20 and PC24, The phenol-oxygenating activity (Kso) was obtainedfrom substrate-dependent oxygen uptake data (oxygen concentrations were measured with aClark-type oxygen electrode) using Michaelis-Mentens model. Specific growth rates µ andlag times). were calculated from absorbance growth curves on phenol concentrations 0,2-10.6mM and the growth kinetic constants (µmax, Ksa, Ki) were estimated using Haldanes, Edwardsand Aiba-Edwards model. The Kso values for phenol were one order of magnitude lower instrains PC 1 and PC 18 than in strains PC20 and PC24.