Optimization of culture conditions for phosphate solubilization by a thermo-tolerant phosphate-solubilizing bacterium Brevibacillus sp. BISR-HY65 isolated from phosphate mines

• We isolated and characterized a thermo-tolerant phosphate solubilizing bacteria.
• Isolate showed high ferric and aluminum phosphate solubilizing abilities.
• Optimization of culturing conditions for high P solubilization was performed.
• HPLC data showed production of organic acids.
• Phylogenetic analysis revealed the bacterium to be Brevibacillus sp.

In the present study we isolated and characterized thermo-tolerant phosphate solubilizing bacteria (PSB) having high ferric phosphate (Fe-P) and aluminum phosphate (Al-P) solubilizing abilities for the first time from rock phosphate mines of Jhamarkotra. Optimization for phosphate (P) solubilization by the isolate BISR-HY65 was performed. Different insoluble P sources viz. hydroxyapatite (H-Ap), Al-P and Fe-P along with rock phosphate (RP) from two different mines of India were used to characterize phosphate solubilizing (PSE) abilities. Optimum conditions found were: temperature 50 °C, pH 7.5, xylose as carbon source, ammonium oxalate as nitrogen source and potassium sulfate as potassium source. Phosphate solubilization was found to be associated with the release of organic acids in culture. HPLC analysis of the culture broth at 96 h of incubation detected four known acids (citric, gluconic, malic and formic acid) along with three unknown acids. Molecular characterization showed our strain to be of Brevibacillus sp.