Use of PhoN Phosphatase to Remediate Heavy Metals

Heavy metals are removed by Serratia sp. via the activity of a cell-bound, atypical, PhoN-type acid phosphatase enzyme, which liberates HPO4^2- from a suitable organic phosphate donor, with the stoichiometric precipitation of heavy-metal cations (M²⁺ ) as insoluble MHPO4 at the cell surface. The present chapter describes the production of Serratia sp. cells (and biofilm) using different growth conditions (i.e., in media containing glycerol and lactose as the carbon source and as batch and continuous cultures). Also, it describes methods of immobilization of cells by entrapment, using polyurethane foam as the matrix, and by covalent coupling, using silanized ceramic Raschig rings and glutaraldehyde as a crosslinking agent. The removal of U from solution using a packed-bed reactor system is described as well as the removal of Ni²⁺ or Co²⁺ using a hybrid bioaccumulative and chemisorptive mechanism, known as “microbially enhanced chemisorption of heavy metals.”