Biodegradation of Pyrene by Free and Immobilized Cells of Herbaspirillum chlorophenolicum Strain FA1

Abstract

Herbaspirillum chlorophenolicum strain FA1, a gram-negative bacterium isolated from activated sludge, was found to be able to use pyrene as sole carbon and energy sources. During biodegradation, the contribution of biosorption to the whole pyrene removal mattered in the early reaction stage, and biodegradation was the predominant process. Pyrene biodegradation was significantly enhanced with the presence of a typical carboxylated aromatic metabolite (phthalic acid) at concentrations of 30–50 mg l−1, and the metabolite itself could also be efficiently biodegraded. For the purpose of practical application, immobilization of strain FA1 was carried out, and polyvinyl alcohol (PVA)-diatomite carrier by chemical method was proved to be the most efficient, with a PYR biodegradation of 92.8 % in 10 days. Investigation on the pyrene biodegradation kinetics by both free and immobilized cells showed that the experimental data fitted well to the first-order kinetic model. Besides, the PVA-diatomite carrier (chemical method) could be reused in at least eight consecutive biodegradation processes of PYR without any significant decrease in biodegradation efficiency. Further storage stability tests revealed that the ability to degrade pyrene using immobilized cells remained stable after storage at 4 °C for 45 days. Moreover, strain FA1 exhibited a relative broad substrate profile, including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, benzo[b]fluoranthene, benzene, toluene, and Tween 80. Taken together, results indicate that strain FA1 might be high potential in the development of treatment technologies for PAHs contamination.