Effective Solubilization of Rock Phosphate by a Phosphate-Tolerant Bacterium Serratia sp.

Abstract

Phosphate-solubilizing bacteria (PSB) can effectively promote the recovery of phosphate-contaminated soil to environmentally safe phosphate levels. The ability and mechanisms of rock phosphate (RP) solubilization were studied using strain LX2 isolated from a phosphate mining wasteland, which was identified as Serratia sp. It was found that strain LX2 could grow at phosphate concentrations of 0–350 mg/L. Optimization of carbon and nitrogen sources was also conducted to increase RP solubilization. and maximum soluble phosphate concentration of 288.69 mg/L with glucose 20 g/L and NH4Cl 0.5 g/L were obtained. The RP solubilization effect under different soluble phosphate concentrations showed that the effective RP solubilization ability by strain LX2 was always accompanied by a decrease in pH. Further, the mechanisms of RP solubilization were studied through Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The presence of strain LX2 caused more corrosive pores on RP surface, which represented the excellent insoluble phosphate solubilization ability. As the soluble phosphate content increased, a gypsum film covered the RP surface, which might prevent further RP solubilization. These results suggested that strain LX2 had great potential in solubilizing RP and could be used as a bioremediation approach of excessive phosphate in phosphate mining wasteland.