ENZYMATICALLY-MEDIATED URANIUM ACCUMULATION AND URANIUM RECOVERY USING A CITROBACTER SP IMMOBILIZED AS A BIOFILM WITHIN A PLUG-FLOW REACTOR

Biofilm-immobilised Citrobacter sp. removed uranyl ion from flows supp lemented with glycerol 2-phosphate. The metal uptake mechanism was med iated by the activity of a cell-surface bound phosphatase that precipi tated liberated inorganic phosphate with uranyl ion as HUO2PO4 . 4H(2) O at the bacterial surface. A modified integrated form of the Michaeli s-Menten equation is proposed to describe the removal of metal ion by a columnar bioreactor, where the efficiency of metal removal is semi-q uantitatively related to the input flow rate, the total enzyme loading (E(0)) and the bioreactor activity. With biofilm-immobilised bacteria , E(0) was further divisible (split) into subparameters of phosphatase titre per bacterium and total biomass surface area. Varying the split E(0) and the reaction temperature modified the bioreactor performance . The immobilised bacteria retained high metal loads without loss in s teady-state activity. Accumulated metal was recovered as a concentrate d solution.