Rapid Biodegradation of Benzo[a]pyrene by Bacillus subtilis BUM Under Thermophilic Condition

Abstract

Abstract

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.