Isolation and characterization of a phenol-degrading bacterium from an industrial activated sludge

Abstract

This paper reports the successful isolation and characterization of a new phenol-degrading bacterium, strain EDP3, from activated sludge. Strain EDP3 is a nonmotile, strictly aerobic, Gram-negative, and short-rod or coccobacillary bacterium, which occurs singly, in pairs, or in clusters. 16S rRNA gene sequence analysis revealed that strain EDP3 belonged to the gamma group of Proteobacteria, with a 97.0% identity to 16S rRNA gene sequences of Acinetobacter calcoaceticus. Strain EDP3 could aerobically grow on a number of aromatic compounds, such as phenol, sodium benzoate, p-hydroxybenzoate, phenylacetate, benzene, ethylbenzene, benzylalcohol, and so on. In particular, it could mineralize up to 1,000 mg l⁻¹ phenol at room temperature (25°C). The growth kinetics of strain EDP3 on phenol as a sole carbon and energy source at 25°C can be described using the Haldane equation. It has a maximal specific growth rate (μ_max) of 0.28 h⁻¹, a half-saturation constant (K _S) of 1,167.1 mg l⁻¹, and a substrate inhibition constant (K _i) of 58.5 mg l⁻¹. Values of yield coefficient (Y _X/S) are between 0.4 and 0.6 mg dry cell (mg phenol)⁻¹. Strain EDP3 has high tolerance to the toxicity of phenol (up to 1,000 mg l⁻¹). It therefore could be an excellent candidate for the biotreatment of high-strength phenol-containing industrial wastewaters and for the in situ bioremediation of phenol-contaminated soils.