Solubilization of inorganic phosphates by Aspergillus awamori S19 isolated from rhizosphere soil of a semi-arid region

A phosphate solubilizing fungus, Aspergillus awamori S19, was isolated from the rhizosphere soil of Pennisetum glaucum grown in semi-arid climatic conditions. The organism was identified on the basis of morphological characterization and by sequencing of ITS1-5.8S-ITS2 region. The organism was able to solubilize various inorganic forms of phosphate at a wide range of temperatures. Amongst various insoluble phosphate sources tested, di-calcium phosphate (DCP) was solubilized the most, followed by tri-calcium phosphate (TCP). The solubilization was evident at all the temperatures but the performance was especially good in the range of 25–35°C. Phosphate-solubilizing ability was also measured in the presence of various carbon and nitrogen sources. Maltose was found to be the best carbon source, followed by glucose, whereas, amongst nitrogen sources, ammonium chloride supported maximum solubilization, followed by ammonium sulphate, sodium nitrate and urea. Ammonium rather than nitrate was found to be more promising as the sole source of nitrogen for phosphate solubilization. The soluble P content was higher when the initial pH for TCP solubilization was 8.0 and optimum concentration for TCP solubilization was 7.5 g l −1 .