Abstract

Phosphate solubilization is an important characteristic of rhizobacteria which help them to contribute substantially to the growth of plants. Phosphate solubilizing bacteria are able to convert insoluble phosphate into forms absorbable by plants, thereby improving the yield of crops. This study investigated the optimization of phosphate solubilization by a consortium of two Pseudomonas spp and two Bacillus spp. isolated from rhizosphere soil from Obio Akpor, Rivers State using response surface methodology based on Box Behnken Design (BBD-RSM). From the data obtained, optimum phosphate solubilization occurred at alkaline pH (pH 8 to 9), inoculum concentration (2.5 to 3.5 %), TCP 1,2,3-Tricalcium phosphate (TCP) concentration (1 to 1.6 mg/L) and mesophilic temperature (33 to 45^oC). However, the highest phosphate solubilization (6.5 mg/L) was achieved specifically at pH 7, inoculum concentration 7.5%, TCP concentration 4 g/L and mesophilic temperature of 35^oC. A significant (p = 0.0225; F = 3.06; R² = 0.7535) quadratic model was obtained for the BBD design, indicating ability of the model to effectively navigate the design space. This study therefore has revealed the capacity of bacterial consortium comprising two Bacillus spp and two Pseudomonas spp isolated from the rhizosphere of maize to solubilize tricalcium phosphate to orthophosphate, a form that is absorbable by plants. This is an indication that this bacterial consortium can be deployed as suitable bioinoculant for enhanced plant growth.