Mechanisms of flame retardant tris (2-ethylhexyl) phosphate biodegradation via novel bacterial strain Ochrobactrum tritici WX3-8

Abstract

Tris (2-ethylhexyl) phosphate (TEHP) is a common organophosphorus flame retardant analog with considerable ecological toxicity. Here, novel strain Ochrobactrum tritici WX3-8 capable of degrading TEHP as the sole C source was isolated. Our results show that the strain's TEHP degradation efficiency reached 75% after 104 h under optimal conditions, i.e., 30 °C, pH 7, bacterial inoculum 3%, and<initial concentration 100 mg L−1. The biodegradation efficiency of cell and intracellular enzymes were 75–76%. A consistent degradation trend was observed, with the cellular surface hydrophobicity being increased from 21 to 58% after 24 h while the biodegradation efficiency being increased from 29 to 59% after 20 h. The data indicate that TEHP increased the cell surface for better biosorption to enter the cell more easily, which was decomposed via intracellular enzymes. Furthermore, the membrane permeability increased with time from 1.22 to 1.39 during 104 h degradation, supporting that TEHP changed the surface structure of cells to promote entry into cells for degradation. Further metabolic pathway analysis revealed the possible TEHP biodegradation metabolic pathway as: tri (2-ethylhexyl) phosphate → di (2-ethylhexyl) phosphate → mono (2-ethylhexyl) phosphate → phosphoric acid and generated 2-ethylhexanol. Results showed that TEHP was transformed by O-dealkylation. This research suggests the viability of using novel strain WX3-8 for TEHP as a cost-effective and environmentally-friendly strategy for bioremediation applications of TEHP in the environment.