Response surface methodology was employed to optimize the composition of medium for phosphate solubilization by Acinetobacter calcoaceticus YC-5a, which is less well known as phosphate solubilizing plant-associated bacteria. (NH4)2SO4, Ca3(PO4)2 and KCl were found to have significant effects on phosphate solubilization by the Plackett-Burman design. The steepest ascent method was used to access the optimal region of the medium composition, followed by an application of response surface. The analysis revealed that the optimum values of the tested variables were (NH4)2SO4 0.2 g/L, Ca3(PO4)2 12.98 g/L and KCl 0.49 g/L, respectively. Phosphate solubilization of 747.72 mg/L, which was in agreement with the prediction, was observed in verification experiment. In comparison to the original level (405.4 mg/L), 1.83-fold increase had been obtained.
Key words: Phosphate solubilizing, Acinetobacter calcoaceticus, medium optimization, response surface.
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