Phenol degrading ability of Rhodococcus pyrinidivorans and Pseudomonas aeruginosa isolated from activated sludge plants in South Africa

Abstract

Phenol, a common constituent in many industrial wastewaters is a major pollutant and has several adverse effects on the environment. The potential of various microorganisms to utilize phenol for their metabolic activity has been observed to be an effective means of remediating this toxic compound from the environment particularly wastewater. Five indigenous bacterial isolates (PD₁-PD₅) were obtained from phenol bearing industrial wastewater using the mineral salts medium. The isolates were further characterized based on their morphology, biochemical reactions and 16S rRNA phylogeny. The 16S rRNA sequence analysis using universal primers (27f/1492r) revealed that PD₁, PD₂, PD₃ and PD₄ were closely related to the actinomycete Rhodococcus pyrinidivorans (99%) and PD₅ to Pseudomonas aeruginosa (99%). Growth kinetic patterns and phenol degradation abilities of the two representative isolates (PD₁ and PD₅) were also evaluated. Both the species were effective in utilizing phenol as the sole carbon source and could tolerate phenol concentrations of up to 500 to 600 mg/L. The ability of these isolates to utilize higher concentrations of phenol as their sole carbon source makes them potential candidates and better competitors in the bioremediation process.

Keywords:

• Activated sludge
• phenol-degrading bacteria
• Pseudomonas
• Rhodococcus
• PCR.

Acknowledgments

The authors wish to thank the Durban University of Technology and the National Research Foundation of South Africa for infrastructural and financial support.