ROCK PHOSPHATE SOLUBILIZATION BY ASPERGILLUS-NIGER GROWN ON SUGAR-BEET WASTE MEDIUM

Solubilization of rock phosphate by Aspergillus niger was studied in s olid-state fermentation on sugar-beet waste. This combination was sele cted after testing three agroindustrial waste materials, namely rice h ulls, sugar-beet waste and alperujo. Sugar-beet waste was the best sub strate for fungal growth with 69% mineralization, followed by rice hul ls and alperujo. The fungus was successfully cultivated on sugar-beet waste supplemented with 3.0 g/l rock phosphate, acidifying the medium and thus decreasing the pH to 3-3.5. Solubilization of insoluble phosp hate increased during the first half of the process, reaching a maximu m of 292 mu g phosphate/ml, although a part of it was probably consume d by the mycelium.