Solubilization of apatite by microbial consortia from activated sludge and rhizospheric soils

Two microbial consortia from activated sludge and rhizospheric soils could effectively solubilize apatite and released soluble phosphate in National Botanical Research Institute's phosphate growth medium. During 14-d incubation, the microbial concentration increased gradually, whereas the pH decreased sharply. The solubilization of apatite by microbial consortium from activated sludge was more efficient than that of microbial consortium from rhizospheric soils. Various organic acids (mainly gluconic acid) were detected in the solution. The solubilization process was also illustrated by the observation of scanning electron microscopy combined with an energy dispersive X-ray spectroscopy, which showed an obvious corrosion on the apatite surfaces, and most elements, especially elements phosphorus and calcium, were removed from the apatite. A strong positive correlation between microbial concentration and content of soluble phosphate was observed, and content of soluble phosphate also had a significant negative correlation with solution pH.