PHOSPHOROUS SOLUBILIZATION FROM PHOSPHATE ROCK BY THE INTERACTIVE EFFECT OF THIOBACILLI AND ELEMENTAL SULFUR

A study was conducted in the Department of Soil Science, Soil and Water Conservation, PMAS Arid Agriculture University, Rawalpindi, Pakistan during the year 2012. In this study sulfuric acid producing capability of Thiobacilli was used in solubilizing phosphorous (P) from phosphate rock. For this purpose, seven Thiobacillus strains (IW1, SW2, SS1, IW13, IW14, IW16 and SM1) were isolated, purified and labeled according to their sampling ecologies. A bioleaching experiment was carried out in shake flasks to test P solubilization ability of Thiobacilli, where phosphate rock, Thiobacillus strains and elemental sulfur as an energy source for Thiobacilli were used. Bacterial sulfur oxidation phenomenon produced higher quantity of sulfuric acid which solubilized huge amount of P from phosphate rock. All Thiobacillus strains had different P solubilizing potential. Maximum solubilization of P was noted in Thiobacillus strain IW16 (8.00 g/L, 61% P) followed by strain SW2 (7.58 g/L, 57.81% P) during 40-days of incubation. Phosphorous solubilization had positive significant correlation with concentration of biologically produced sulfates and negative significant correlation with pH of leach solutions.