Optimisation de la solubilisation du phosphate par des rhizobactéries

Abstract

Phosphate solubilizing bacteria play a vital role in soil fertility, which they are used to promote the growth of a large group of plants.The aim of this work is the evaluation the capacity of bacterial isolates to release inorganic phosphate and optimizing their solubilization. Different culture media, nitrogen source and carbon source were used under varying culture conditions for optimizing solubilization of phosphate by two bacteria isolated from saline soil A1 and A2. The study of solubilization of tricalcium phosphate by the bacterial isolates on PVK solid medium showed that the highest solubilization efficiency was observed with the isolate A2 (2228.57%). The comparison of amounts of phosphorus released by the isolates in different liquid cultures showed that the best solubilization was obtained in NBRIP medium for both A1 and A2 isolates with quantities of 651.619 μg / ml and 560.667 μg / ml of free phosphorus respectively. Glucose was found to be the best source of carbon for solubilization of phosphate by the two isolates. The effect of the variation of nitrogen source in the medium allowed to select ammonium sulfate )NH4(2SO4 as the most favorable nitrogen source for both bacterial isolates. The results showed that the pH = 5 and the incubation temperature of 30C° are optimal conditions for solubilization for the bacteria used. The study of the effect of incubation time led to select the 6th day of incubation as an optimal time for phosphate solubilization by the two isolates.