ROCK PHOSPHATE SOLUBILIZATION AND ENZYMATIC ACTIVITIES FROM INDIGENOUS BACTERIA ON CASSAVA MILL EFFLUENT CONTAMINATED SOIL

The processing of cassava into value-added products is associated with discharge of effluents which contain substances that have adverse effect on the environment. Remediative activity of indigenous bacteria can be stimulated by supplementing effluents with phosphorus. Rock phosphate (RP) solubilization and enzymatic activities from bacteria on the cassava mill effluents (CME) contaminated soil was investigated. Soil mixed with varying concentrations of CME (0, 100, 200, 300, 400, 500 and 600 ml) and 10 g of RP were analyzed on days 0 and 16. Parameters analyzed were changes in pH, heterotrophic bacteria load, phosphate-solubilizing bacteria load, available phosphorus, acid phosphatase, cellulase and urease concentrations. The results showed that the medium containing 400 ml CME contaminated soil had the highest phosphate-solubilizing bacteria load (12.60 ± 2.08 x 106 cfu/ml), available phosphorus (126.00 ± 4.08 mg/kg), acid phosphatase (9.54 ± 0.51 mgN/g/min), cellulase (15.24 ± 0.81 mg/g/6h) and urease concentration (2.15±0.22 mg/g/2h). The control had the lowest phosphate-solubilizing bacteria load and enzymatic activity. Biostimulation of indigenous bacteria to enhance the degradation of cassava mill effluent-contaminated soil, using rock phosphate, showed promising results. This implies that rock phosphate solubilization by indigenous bacteria in CME-contaminated soils could be important for the remediation and reclamation of contaminated lands.