Isolation, Molecular, and Metabolic Profiling of Benzene-Remediating Bacteria Inhabiting the Tannery Industry Soil

Benzene is a pervasive contaminant and human carcinogen. Its remediation from environmental resources using conventional procedures has always been challenging due to high cost and incomplete benzene degradation. The present study was designed to explore highly efficient bacteria with benzene degrading potential from tannery industry soil, which might be used as an alternative to these conventional benzene removal remedies. Bacterial isolation was performed using benzene (80 μl/1,000 ml) supplemented with minimal salt media (MSM). Characterization of isolates was carried out by performing growth curve analysis, Gram staining, biochemical characterization via Remel RapID™ NF PLUS System (Thermo Scientific™, Thermo Fisher Scientific, Inc., USA), antibiotic sensitivity profiling, 16S rRNA gene sequencing, benzene removal efficiency estimation assay, FTIR, and GC-MS profiling. Five bacteria isolated in the present study were identified as Paracoccus aestuarii PUB1, Bacillus tropicus PUB2, Bacillus albus PUB3, Bacillus subtilis PUB4, and Bacillus cereus PUB6. All of these fast-growing bacteria were Gram-positive except P. aestuarii PUB1. Maximum benzene removal efficiency (30 mg/l per 25 h) was found in B. tropicus PUB2. Comparing the FTIR spectra of bacterial culture supernatant versus control revealed the peaks shifting corresponding to benzene ring bonds breaking. GC-MS analysis identified the metabolic intermediates from benzoate methylation and benzaldehyde pathways. These bacteria can be employed for benzene degradation via enzyme-based nanoparticle synthesis or cloning of relevant genes in eco-friendly expression systems.