Synthesis of nanophase hydroxyapatite by a Serratia sp. from waste-water containing inorganic phosphate

Synthesis of nanophase hydroxyapatite (HA) on a bacterial surface was achieved at the expense of CaCl2 and inorganic phosphate (Pi). After initial nucleation, calcium was precipitated on and around the cells as calcium phosphate at the expense of inorganic phosphate in the challenge solution, with no precipitation in cell-free controls. HA was also biomanufactured using inorganic phosphate ions scavenged from a phosphate-containing waste-water. With additional Ca2+, the concentration of phosphate was decreased from 0.27 (approximately 25 ppm) to approximately 0.02 m (approximately 2 ppm) in the waste-water. Crystals of calcium phosphate manufactured by the cells were located by scanning electron microscopy (SEM) and identified as HA by X-ray powder diffraction, with an average crystal size calculated as approximately 25 nm. Possible application of bioHA as a biomaterial and implications for one-step 'waste-into product' are discussed.