Rapid biodegradation of benzo[a]pyrene by bacillus subtilis BUM under thermophilic condition

Two thermophilic bacterial strains, Bacillus subtilis BUM (BUM) and Mycobacterium vanbaalenii BU42 (BU42), were tested for their potential in biodegradation of benzo[a]pyrene. Neither BUM nor BU42 utilized benzo[a]pyrene as the sole substrate under thermophilic condition. In the presence of 50, 250, and 500 mg L^-1 phenanthrene, the biodegradation of benzo[a]pyrene by BUM occurred and removals in 30 days were 14.8%, 38.8%, and 63.6%, respectively. This is the first report on the biodegradation of benzo[a]pyrene by isolated thermophilic microorganism. The BUM strain was further tested for its ability in a soil composting system. Within a composting period of 42 days, removal of benzo[a]pyrene in the absence of BUM was 30.3%. Treatment with the inoculation of BUM significantly increased the removal of benzo[a]pyrene to 52.2%. Maximum zero-order degradation rates of benzo[a]pyrene by BUM in aqueous biodegradation experiment and soil composting system were 12.3 mg L^-1 day ^-1 and 9.7 mg kg^-1 day^-1, respectively, which were significantly greater than most of the reported degradation rates by mesophiles. Experimental results affirmed that the strain BUM can effectively degrade benzo[a]pyrene under thermophilic condition.