Benzene Biodegradation by Novel Strain of Caldibacillus: Isolation, Characterization and Bioremediation Potential

Benzene pollution presents notable health hazards to individuals exposed in industrial settings or accidents, due to its persistent and water-insoluble nature. Eliminating benzene is crucial for safeguarding human health and environmental wellbeing. In this study, a soil sample was collected from a polluted semi-arid soil in the industrial estate of Al-mafraq city, Jordan. A new bacterial strain, designated as EJ2, was isolated from this polluted soil using mineral Stanier's medium (MSM) enriched with 1% benzene after multiple culture transfers. The isolated strain underwent biochemical and molecular identification for characterization. The isolate was cultured in enriched MSM with varying benzene concentrations (1, 2 and 3%), at pH values of 6.8 and temperature of 30?C. The strain displayed motile, Gram-positive bacilli with spore formation capability under light microscope examination. Biochemical testing indicated that this strain was positive for oxidase and catalase, while it exhibited the ability to hydrolyze carbohydrates and other organic compounds. 16S rRNA gene sequence analysis and BLAST searches against DNA sequence databases revealed that the new strain is a member of the genus Cladibacillus (Family Bacillaceae, Domain Bacteria) with the closest related species being Cladibacillus sp., showing a sequence identity of 99.09%. Most importantly, the strain exhibited growth when exposed to MSM containing benzene as the only carbon and energy substrate, within concentrations of 1 to 3%. Isolate EJ2 exhibited enhanced benzene degradation at a 1% concentration, with a generation time of 6.2 h, surpassing previously isolated Lysinibacillus strains (7.7-9.1 h) from the same soil source. The study identifies EJ2, a bacterium belonging to the Caldibacillus genus, as benzene-utilizing, suggesting promise for biodegradation. Therefore, additional research is crucial for understanding the metabolic pathways and processes of this novel isolate, thus optimizing its biodegradation capacity.