Metabolic biotransformation of copper–benzo[a]pyrene combined pollutant on the cellular interface of Stenotrophomonas maltophilia

• Cell wall was the main adsorption site for Cu but was a barrier to transport BaP.
• A part of Cu(II) changed into Cu(I) and Cu on the cell surface by S. maltophilia.
• Multiple mechanisms worked together to promote the removal of Cu by the strain.
• BaP took ring opening reaction on the cell surface that affected Cu biosorption.

Previous studies have confirmed that Stenotrophomonas maltophilia can bind an appreciable amount of Cu(II) and degrade BaP. However, the removal mechanisms of Cu(II) coexisted with BaP by S. maltophilia are still unclear. In this study, the micro-interaction of contaminants on the cellular surface was investigated. The results indicated that carboxyl groups played an important role in the binding of copper to the thallus and that the cell walls were the main adsorption sites. Nevertheless, these reactive groups had no obvious effect on the uptake of BaP. Instead, the disruption and modification of cell walls accelerated transportation of BaP across the membrane into cells. The observation of SEM–EDS confirmed that Cu(II) would be adsorbed and precipitated onto the cell surface but would also be removed by extracellular precipitation when BaP coexisted. And the XPS analysis reflected that part of Cu(II) bound onto biosorbents changed into Cu(I) and Cu.

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