| Three strains of thermophilic phosphate solubilizing microorganisms named P1, P2, P3, were selected and mixed as multiple species inoculants（MSI） according to Simple-centroid method with Design Expert software. Then quadratic polynomial mathematical model of the solubilized-phosphorus condition of thermophilic MSI was established by response surface methodology（RSM）. Compared with seven levels, the results showed that the Phosphate-solubilizing quantity of P1∶P2∶P3=0∶50%∶50%（241.70 mg·L-1） level was significantly higher than other MSI. Based on the design of Box-Behnken to optimize the optimal levels and the interaction of five important factors which included the incubation time（x1）, the incubation temperature（x2）, pH（x3）, the content of rock phosphate（x4）, the inoculum size of microorganism（x5）. The results showed that：（1）Linear term of incubation time and pH, interaction term of incubation time and pH, interaction term of incubation time and content of rock phosphate, interaction term of incubation temperature and content of rock phosphate, quadratic term of all the variable were reached extremely significant level（P<0.01）.（2）Incubation time and pH were the key factors on solubilized-phosphorus capability using MSI. The influence of other factors was the inoculum size of microorganism>rock phosphate proportion>temperature.（3）The optimized result of the solubilized-phosphorus condition of thermophilic compound bacterium was as follows：the inoculum size of microorganism was 6.07%, and the content of rock phosphate was 6.21 g·L-1 with the incubation temperature at 49.98 ℃ for 7.18 d under 6.63 pH value. Verification tests show that the response surface methodology can scientific and effective build a thermophilic compound bacterium model, reasonably optimize the influencing factors of the solubilizing conditions. |
