Biochemical pathways and enhanced degradation of endocrine disruptor di-2-ethylhexyl phthalate by an indigenous isolate Bacillus sp. MY156

Abstract

Di-2-ethylhexyl phthalate (DEHP) widely exists in the environment and has raised an increasing global concern. A bacterial strain capable of degrading DEHP was isolated from the activated sludge at a local wastewater treatment plant and identified as Bacillus sp. MY156. A nearly complete degradation of DEHP at 500 mg L−1 was reached within 5 days when MY156 was grown at pH 8 and 30 °C. The biodegradation of DEHP (50–600 mg L−1) followed the first-order kinetics. Mass balance analysis showed the efficient degradation of DEHP with the ratio of biomass to DEHP at 0.72. The dehydrogenase activity was positively related to the biodegradation of DEHP, while the extracellular polymeric substance (EPS) might have played a key role in overcoming the potential inhibition caused by DEHP. The microelements (Fe3+, Zn2+, and Mn2+) supplements stimulated the DEHP degradation while copper (Cu2+) showed inhibitory. The proposed intermediate metabolites of the DEHP degradation included mono-ethylhexyl phthalate, diethyl phthalate, dimethyl phthalate, phthalic acid, and protocatechuate. Together with the micro-morphological observation, biodegradation experiments in saline and different real water environments suggested the isolate possessing strong halo-tolerance and potential applicable ability to adapt to various environmental conditions. The isolate could be used as a potential and efficient phthalic acid esters (PAEs) degrader for the bioremediation of contaminated sites.