Modeling Phosphate Solubilization by Pseudomonas fluorescens Using Response Surface Methodology

Phosphorus is one of the most important limiting elements for plant growth. Using phosphate solubilizing microorganisms (PSM) is one of the main strategies to meet plant P demand. In Vitro screening of phosphate solubilization potential in order to use as biofertilizers, is influenced by nutrient composition of media. The purpose of this study was modeling the effects of different carbon and nitrogen sources and tricalcium phosphate on phosphorous solubilization using Placket-Burman design and response surface methodology with a central composite design. At the first step, 12 experiments based on Placket-Burman design were carried out to screen and identify the effective carbon and nitrogen sources in phosphorous dissolution by Pseudomonas fluorescens. Results indicated that yeast extract was more effective source of nitrogen in comparison with other nitrogen sources. According to the results of the first step, response surface methodology with central composite design was employed to evaluate and to model the effects of sucrose, yeast extract and tricalcium phosphate concentrations on phosphate dissolution. The analysis of variance (ANOVA) depicted the high performance of the central composite predictive model of phosphorus dissolution (R2= 0.896 and RMSE=0.0372 g L-1). The yeast extract and tricalcium phosphate were the most significant parameters for phosphate solubilization. Increasing of the yeast extract concentration at the range of 0-4 g L-1 and the tricalcium phosphate at the range of 0-20 g L1 significantly increased the soluble phosphate concentration. According to central composite design, maximum phosphate dissolution was obtained at the yeast extract, sucrose and tricalcium phosphate concentrations of 4, 18.58, 17.97 g L1 respectively.