Microbially enhanced chemisorption of nickel into biologically synthesized hydrogen uranyl phosphate: A novel system for the removal and recovery of metals from aqueous solutions

Genetics of phosphate solubilization and its potential applications for improving plant growth-promoting bacteria

“…Macaskie et al (1997) reported on the successful use of Class A NSAPs as tools for environmental bioremediation of uranium-bearing wastewater, and Baskanova and Macaskie (1997) and Bonthrone et al (1996) on heavy metal biomineralization (particularly Ni 2+ ). A new biotechnological application for NSAPs would be to transfer and express these genes in PGPB to obtain improved phosphatesolubilizing strains using recombinant DNA technology.…”

Accumulation of zirconium and nickel byCitrobacter sp

“…Ni 2+ was reversibly intercalated; cell-bound hydrogen uranyl phosphate could be regenerated and used in sequential Ni sorption/ desorption cycles. 4,5 These ®ndings con®rmed the viability of a general concept of`Microbially Enhanced Chemisorption of Heavy Metals' (MECHM), describing a hybrid mechanism of metal bioaccumulation via intercalation into preformed, biogenic crystals. 1 The biogenic`host' crystal, hydrogen uranyl phosphate, was preformed via biomineralization of the uranyl cation (UO 2 2 )`priming metal' with hydrogen phosphate (HPO 2À 4 ) ligand, which was generated in situ from externally provided glycerol-2-phosphate (G2P) by the action of an acid phosphatase (PhoN) of a naturally-occurring Citrobacter sp 1 or Escherichia coli bearing the corresponding cloned phoN gene.…”

“…1,3,4 Biomass was grown aerobically in two independent 3 dm 3 batch cultures (batches I and II) at 30°C with lactose as the carbon source and ammonium phosphate as the combined nitrogen and phosphate source, in minimal medium comprising: 4 Tris±(hydroxymethyl)aminomethane buffer (Tris; 12 g dm À3 ), lactose (®lter sterilized; 2.13 g dm À3 ), (NH 4 ) 2 HPO 4 (0.96 g dm À3 ), KCl (0.62 g dm À3 ), MgSO 4 Á7H 2 O (0.063 g dm À3 ), and FeSO 4 Á7H 2 O (0.00032 g dm À3 ), pH 7 (with HCl). The cultures were harvested by centrifugation in the stationary phase (24 h) and the phosphatase speci®c activity was determined by liberation of p-nitrophenol from pnitrophenyl phosphate 26 as 1367 and 1550 nmol p-nitrophenol min À1 per mg of protein for batches I and II, respectively.…”

“…2 An effective removal of nickel from dilute aqueous¯ows was achieved by employing intercalative ion exchange of nickel into biologically-synthesized crystalline hydrogen uranyl phosphate (HUO 2 PO 4 .4H 2 O, HUP). 3,4 The resulting, biomass-bound, crystalline deposit was identi®ed as nickel uranyl phosphate (Ni(UO 2 PO 4 ) 2 .7H 2 O). Ni 2+ was reversibly intercalated; cell-bound hydrogen uranyl phosphate could be regenerated and used in sequential Ni sorption/ desorption cycles.…”

“…For Zr 4 23 Increase of pH by addition of base or heating of an aqueous solution of zirconyl chloride resulted in polymerization and eventual precipitation of gelatinous material. After subsequent centrifugation, washing and air drying this was identi®ed by X-ray diffraction analysis as hydrous zirconia (ZrO 2 )n, containing a signi®cant amount of coordinated water and hydroxy groups and having ionexchange properties.…”