Characterization of brushite as a re-crystallization product formed during bacterial solubilization of hydroxyapatite in batch cultures

• Published in: Soil biology & biochemistry Vol. 38; no. 9; pp. 2645 - 2654
• Main Authors: Delvasto, P., Valverde, A., Ballester, A., Igual, J.M., Muñoz, J.A., González, F., Blázquez, M.L., García, C.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2006; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Brushite; Burkholderia; Burkholderia caribiensis; Burkholderia sp; Calcium phosphate-solubilizing microorganisms; Chemical, physicochemical, biochemical and biological properties; crystallization; Fundamental and applied biological sciences. Psychology; High-phosphorus iron ore; Hydroxyapatite; Physics, chemistry, biochemistry and biology of agricultural and forest soils; soil bacteria; Soil science; solubilization; strains; Brazil; Brushite; High-phosphorus iron ore; Hydroxyapatite; Burkholderia sp; Burkholderia caribiensis; Calcium phosphate-solubilizing microorganisms; Crystallization; Calcium phosphate; Phosphorus; Iron ore; Calcium Hydrogenphosphates; Batch process; Bacteria; Soil science; Microbial solubilization; Burkholderia
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2006.03.020

Two strains of bacteria ( Burkholderia sp., strain FeGL01, and Burkholderia caribiensis, strain FeGL03) were isolated from a Brazilian high phosphorus iron ore. The capacity of both strains to solubilize hydroxyapatite, Ca 5(PO 4) 3(OH), was assessed in plate and batch cultures. In batch cultures, the concentration of solution-P showed two kinetics: an initial one, characterized by a continuously increasing kinetics and a second one, characterized by oscillatory kinetics. To understand the nature of these oscillations, phosphatic residues in the spent broth were collected before, during and after the oscillations, and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray chemical microanalyses (EDX) and X-ray diffraction (XRD). From these studies, it was found that drops in P concentration were related to the formation of an intermediate phosphate in the residues, identified as brushite, CaHPO 4·2H 2O. Later increase of available P in the solution was found to be a consequence of re-dissolution of brushite crystals previously formed. Re-crystallization of brushite was also detected in plate cultures after 12–14 days of incubation