PAH biotransformation and sorption by Fusarium solani and Arthrobacter oxydans isolated from a polluted soil in axenic cultures and mixed co-cultures

Abstract

The polycyclic aromatic hydrocarbon (PAH) dissipation potential of Fusarium solani MM1 and Arthrobacter oxydans MsHM11, isolated from a PAH-polluted soil, was investigated in liquid cultures containing 500, 500, and 50mgl−1 of phenanthrene (PHE), pyrene (PYR), and dibenz(a,h)anthracene (DBA), respectively. The contributions of adsorption, absorption and biotransformation were evaluated separately by extracting and analysing PAHs from the biomass and from the culture medium. In the pure culture, F. solani dissipated approximately 30% of each tested PAH in 28 days when glucose was supplied as the carbon source. PAH adsorption on F. solani hyphae was negligible, whereas absorption was found to account for one-third of the dissipation. Absorbed PAHs, reaching 3% of the fungal dry biomass, could be visualised in autofluorescent intracellular vesicles. In contrast, A. oxydans grew on PAHs as sole carbon source and led to 55% dissipation of PHE in 28 days without any significant absorption. This dissipation potential was inhibited by the presence of glucose, and the PYR and DBA contents were never dissipated in the bacterial pure culture. In the mixed co-culture, the PAH dissipation rates were lower, showing that antagonistic interactions, such as pH changes or competition for carbon source, indirectly inhibited both microbial potentials.