Biodegradation of benzo(a)pyrene by Microbacterium sp. strain under denitrification: Degradation pathway and effects of limiting electron acceptors or carbon source

Abstract

Being electron acceptors, the amount of nitrate (nitrite) significantly affect the benzo(a)pyrene (BaP) biodegradation of Microbacterium sp. under denitrifying conditions. In the study, the degradation behavior of Microbacterium sp. and the concentration variations of electron acceptors were investigated at different concentration ratios of BaP/nitrate (nitrite). The results showed that compared with reductions in BaP concentration, the extent of BaP degradation and denitrification was significantly affected by C/N ratios. The Microbacterium sp. strain could use the denitrifying products nitric oxide and nitrous oxide as electron acceptors to degrade BaP and the shortage of electron acceptors did not decrease the BaP removal rates but lead to a decrease in the BaP degradation. The degree of degradation of BaP could be controled by adding appropriate nitrate (nitrite) which calculated based on the fitting equations of the relationship between nitrate (nitrite) consumption and BaP removal amount. The Microbacterium sp. strain performed better under nitrate-reducing condition, and the highest removal rate (84.2%) was obtained at the BaP/nitrate ratio of 1:33 in 10 d. This study will help further mechanism investigation of anaerobic BaP degradation and the conduct of the PAHs bioremediation by adding exogenous electron acceptors.