Solubilization of insoluble inorganic phosphates by a novel salt- and pH-tolerant Pantoea agglomerans R-42 isolated from soybean rhizosphere [An article from: Bioresource Technology]

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Description:
To develop environment-friendly biofertilizer solubilizing insoluble phosphates, salt- and pH-tolerant, insoluble inorganic phosphate-solubilizing bacterium was isolated from soybean rhizosphere. On the basis of its physiological characteristics and Vitek analysis, this bacterium was identified as Pantoea agglomerans. The optimal medium composition and cultural conditions for the solubilization of insoluble phosphate by P. agglomerans R-42 were 3% (w/v) of glucose, 0.1% (w/v) of NH"4NO"3, 0.02% (w/v) of MgSO"4.7H"2O, and 0.06% (w/v) of CaCl"2.2H"2O along with initial pH 7.5 at 30^oC. The soluble phosphate production under optimal condition was around 900mg/l, which was approximately 4.6-fold higher than the yield in the MPVK medium. The solubilization of insoluble phosphate was associated with a drop in the pH of the culture medium. P. agglomerans R-42 showed resistance against different environmental stresses like 5-45^oC temperature, 1-5% salt concentration and 3-11 pH range. Insoluble phosphate solubilization was highest from CaHPO"4 (1367mg/l), hydroxyapatite (1357mg/l) and Ca"3(PO"4)"2 (1312mg/l). However, the strain produced soluble phosphate to the culture broth with the concentrations of 28mg/l against FePO"4, and 19mg/l against AlPO"4, respectively.