Biodegradation of polycyclic aromatic hydrocarbons by a mixed culture

We investigated the potential biodegradation of polycyclic aromatic hydroca rbons (PAHs) by an aerobic mixed culture utilizing phenanthrene as its carb on source. Following a 3-5 h post-treatment lag phase, complete degradation of 5 mg/l phenanthrene occurred within 28 h (optimal conditions determined as 30 degrees C and pH 7.0). Phenanthrene degradation was enhanced by the individual addition of yeast extract, acetate, glucose or pyruvate. Results show that the higher the phenanthrene concentration, the slower the degrad ation rate. While the mixed culture was also capable of efficiently degradi ng pyrene and acenaphthene, it failed to degrade anthracene and fluorene. I n samples containing a mixture of the five PAHs, treatment with the aerobic culture increased degradation rates for fluorene and anthracene and decrea sed degradation rates for acenaphthene, phenanthrene and pyrene. Finally, i t was observed that when nonionic surfactants were present at levels above critical micelle concentrations (CMCs), phenanthrene degradation was comple tely inhibited by the addition of Brij 30 and Brij 35, and delayed by the a ddition of Triton X100 and Triton N101. (C) 2000 Elsevier Science Ltd. All rights reserved.