Enhanced degradation of fluorene in soil slurry by Absidia cylindrospora and maltosyl-cyclodextrin

This study investigates the fungal biodegradation of fluorene, a polycyclic aromatic hydrocarbon, in liquid medium and soil slurry. Fungal strains and cyclodextrins were used in order to degrade fluorene and optimize fluorene bioavailability and degradation in soil slurries. After a procedure of selection in solid and liquid media, maltosyl-cyclodextrin, a branched cyclodextrin was chosen. 47 fungal strains isolated from a contaminated site were tested for biodegradation. Results showed the greater efficiency of "adapted" fungi isolated from contaminated soil vs reference strains belonging to the collection of the laboratory. These assays allowed us to select the most efficient strain, Absidia cylindrospora, which was used in a bioaugmentation process. Bioaugmentation tests were performed in an artificially contaminated non-sterile soil. In the presence of A. cylindrospora, more than 90% of the fluorene was degraded within 288 h, while 576 h were necessary in the absence of fungal bioremediation. It also appeared that biodegradation was enhanced by amendment with previously selected maltosyl-cyclodextrin. The results of this study indicate that A. cylindrospora and maltosyl-cyclodextrin could be used successfully in fluorene bioremediation systems.