Strain Improvement Of A Potent Benzo-A-Pyrene (Bap) Degrader Bacillus Subtilis Bmt4i (Mtcc 9447)1

Benzo [a] pyrene (BaP), a pentacyclic polyaromatic hydrocarbon, is 1 of the 12 target compounds defined in the new US Environmental Protection Agency's strategy for controlling persistent, bioaccumulative, and toxic pollutants. We previously isolated a novel strain Bacillus subtilis BMT4i (MTCC) capable of utilizing BaP as sole source of carbon and energy and degrading BaP via an inducible chromosomally encoded pathway. The present study was done to improve the BaP degradation ability of B. subtilis BMT4i by means of inducing random mutations through treating BMT4i with physical mutagen (UV irradiation) or chemical mutagens such as ethyl methane sulfonate (EMS), 5-bromo uracil (5-BU) and acridine orange (AO). The observation showed that a UV mutant BMT4imuv2, amongst various other mutants exhibited highest BaP degradation up to 62% which was significantly superior in comparison to the control wild type BMT4i that showed 46% BaP degradation. The BMT4imuv2 was further characterized by time course experiment which showed almost 100% BaP degradation on completion of 28 days in contrary to 84.66% by control wild type BMT4i confirming a substantial improvement of the BaP degradation potential of BMT4i after treatment with physical mutagen UV (254 nm). The growth scenario of the mutant was found to be somewhat different. BMT4imuv2 showed a steep increase in the log values reaching to 16.60 after 2 days attaining maxima of 45.47 log10 CFU/ml after 7 days. Further, increase in incubation period led to decline in the cell number reaching 0.00 after 28 days. In view of the above, it could be concluded that BMT4imuv2 is an improved version of BMT4i having a superior capability of BaP degradation, hence it could serve as a leading biological weapon to remediate BaP contaminated sites.