Optimization of phosphate solubilization by Aspergillus niger using plackett-burman and response surface methodology

Phosphorus is one of the major components required for the metabolic activities and for the growth of any organism. Many soil organisms are known to solubilize inorganic phosphates. Aspergillus niger isolated from the soil showed extensive solubilization of Tri-calcium phosphate.It was observed that the solubilization was due to drop in pH.Acidification was due to production of organic acids by the fungi. The effect of different medium components on the solubilization of phosphate was determined using the Packett-Burman design. It was observed that glucose and ammonium sulphate had significant effect on phosphate solubilization. Considering the Plackett-Burman results, the response surface methodology was used for optimization of these medium components along with tri-calcium phosphate on P-solublization. The analysis from RSM revealed that the optimum values for the tested variables were glucose 2g/50ml, ammonium sulphate –0.2g/50ml and tricalcium phosphate 1g/50ml. Phosphate solubilization of 3.64 mg/ml was observed as comparison to original level of 1.88mg/ml, which was a 1.93-fold increase was obtained. From the HPLC analysis it was observed that oxalic acid and lactic acid were the major acids responsible for enhancing the P solubilization.