Aerobic Bacterial Degraders With Their Relative Pathways for Efficient Removal of Individual BTEX Compounds

Benzene, toluene, ethylbenzene, and xylene (BTEX) compounds are of great environmental concern due to their toxicity and carcinogenicity. Bacterial removal of BTEX has proven to be highly efficient, cost‐effective, and non‐disruptive, provided that, efficient bacterial degraders are available. The objective of this study, therefore, is to discover aerobic bacterial degraders with their relative pathways that could be employed for the efficient removal of individual BTEX compounds. A total of 22 petroleum hydrocarbon degrading aerobic bacteria from the river water in close vicinity to a petrol refinery were isolated and identified previously. These bacteria were further screened for their potential to degrade individual BTEX compounds. Primary selection of BTEX degraders was carried out by using conventional enrichment culture technique and gas chromatography/mass spectrophotometry (GC/MS) analyses. Out of the 22 isolates, five were found to degrade BTEX efficiently and further characterized through PCR analyses for their initial attack and cleavage genes as well as GC/MS analyses of the intermediate metabolites to decipher the degradation pathways used. The study elucidates new efficient bacterial strains of Acinetobacter calcoaceticus Fe10, Serratia nematodiphila Mn11, Raoultella planticola Ag11, Pseudomonas koreensis Hg11, and Micrococcus luteus Sr11 with their relative pathways for aerobic removal of the individual BTEX compounds. Individual BTEX degraders are evaluated by using PCR and GC/MS analyses. R. planticola Ag11 and M. luteus Sr11 are found to metabolize benzene over phenol. Toluene is degraded by M. luteus Sr11 through ring mono‐oxidation. A. calcoaceticus Fe10 metabolizes toluene through oxidation of the methyl group, and ethylbenzene is mostly metabolized over the styrene pathway. The isomeric forms of xylene are only metabolized by A. calcoaceticus Fe10.