Repeated use of Bacillus subtilis cell walls for copper binding.

Purified cell walls from Bacillus subtilis were repeatedly suspended in 5 mM CuCl2 and, after removing unbound Cu, were suspended in 1% (v/v) HNO3 to release bound Cu. The walls were then regenerated by washing in H2O. After five cycles, copper binding actually increased slightly, probably due to enhanced exposure of binding sites in the walls. Thus bacterial walls may be used repeatedly for metal removal during bioremediation of heavy metal pollution.