Benzo [a] Pyrene (BaP) is a highly recalcitrant, polycyclic aromatic hydrocarbon (PAH) with high genotoxicity and carcinogenicity. It is formed and released into the environment due to incomplete combustion of fossil fuel and various anthropogenic activities including cigarette smoke and automobile exhausts. The aim of present study is to isolate bacteria which can degrade BaP as a sole source of carbon and energy. We have isolated a novel strain BMT4i (MTCC 9447) of Bacillus subtilis from automobile contaminated soil using BaP (50 g /ml) as the sole source of carbon and energy in basal salt mineral (BSM) medium. The growth kinetics of BMT4i was studied using CFU method which revealed that BMT4i is able to survive in BaP-BSM medium up to 40 days attaining its peak growth (10(29) fold increase in cell number) on 7 days of incubation. The BaP degradation kinetics of BMT4i was studied using High Performance Liquid Chromatography (HPLC) analysis of BaP biodegradation products. BMT4i started degrading BaP after 24 hours and continued up to 28 days achieving maximum degradation of approximately 84.66 %. The above findings inferred that BMT4i is a very efficient degrader of BaP. To our best of knowledge, this is the first report showing utilization of BaP as a sole source of carbon and energy by bacteria. In addition, BMT4i can degrade a wide range of PAHs including naphthalene, anthracene, and dibenzothiophene therefore, it could serve as a better candidate for bioremediation of PAHs contaminated sites.
Keywords: Bacillus subtilis BMT4i; Benzo [a] Pyrene (BaP); colony forming units/ml (CFU/ml); high performance liquid chromatography (HPLC); polycyclic aromatic hydrocarbon (PAH).