Isolation of fluorene degrading microorganisms from sediments of the Southern Caspian Sea Coasts and evaluation of their bioremediation potential

Polycyclic aromatic hydrocarbons are one of the most important environmental pollutants. Bioremediation using microorganisms is a cost-effective and safe method for the removal or conversion of these pollutants to less toxic substances. This study aimed to isolate and introduce fluorene-degrading microorganisms from the southern coast of the Caspian Sea. The mixed microbial culture enrichment and isolation was done in salt-based culture medium containing fluorene. The qualitative analysis of fluorene degradation in the solid basal salt medium was investigated. The rate of fluorene removal by the isolated mixed microbial culture was also determined using gas chromatography in a liquid salt base medium. The molecular identification of the fungal and bacterial isolates was performed using the sequential analysis of the ITS protected region and 16S rRNA sequencing, respectively. The mixed microbial culture including bacterial isolates (belonging to the genus Pseudomonas, Acromobacter, Chryseobacterium, Microbacterium, and Rhodococcus) and fungal isolate (belonging to the genus Fusarium) was enriched and isolated. Chromatographic analysis showed that the mixed microbial culture was able to degrade 87% of fluorene (200 mg / l ) in a basal salt medium at 30 °C, pH 7 and 7 days of incubation. According to the results, the mixed microbial can remove a large amount of fluorene from the basal salt medium under the mentioned conditions and it is possible that under a similar situation, it can remove a large amount of fluorene from the contaminated area through bioremediation.