Proposal of possible pathway of fluorene biodegrada-tion by Citrobacter sp. FL5

Abstract

The biodegradation ability of Citrobacter sp. FL5 on fluorene was investigated in the present study. The bac-terial isolate was identified based on biochemical test, physiological and 16S rDNA sequence analysis. Fluorene biodegradation was studied in the liquid media at the initial concentration of 50 mg L−1 fluorene at different pH values (6, 7, 8 and 9) and temperatures (25, 30, 37 and 45°C). Citrobacter sp. FL5 showed maximum performance of fluorene degradation ability at pH 7 and 30°C where it degrades 98% fluorene in liquid media. Furthermore, the isolate degrades 97.5% and 96% of 100 and 150 mg L–1 fluorene respectively at 168 hrs. The possible metabolic pathway for fluorene biodegradation by Citrobacter sp. FL5 was deduced by identification of metabolites through Gas Chromatography Mass Spectrometry (GC-MS) technique. 5 types of metabolites that were detected and identified were dibenzofuran, 9-fluorenylmethanol, methyl benzilate, piperonylic acid and catechol. This study was the first to report and describe the ability of Citrobacter sp. in detail for degradation of higher fluorene concentrations at various pH and temperatures ranges.