PhoN-expressing, lyophilized, recombinant Deinococcus radiodurans cells for uranium bioprecipitation

Employment of genetically engineered radiation resistant organisms to recover radionuclides/heavy metals from radioactive wastes is an attractive proposition. Cells of recombinant Deinococcus radiodurans strain expressing, a non-specific acid phosphatase encoding phoN gene, were lyophilized. Lyophilized recombinant Deinococcus cells retained viability and PhoN activity and could efficiently precipitate uranium from aqueous solutions for up to six months of storage at room temperature. Batch process for uranium removal using lyophilized cells was more efficient compared to a flow through system, in terms of percent uranium removed, substrate conservation and time taken. Lyophilized recombinant Deinococcus cells exhibited high loading of up to 5.7 g uranium/g dry weight of cells in a batch process at 20 mM input uranium concentration. Lyophilization deflated the cells but did not alter gross cell morphology or surface nucleation capability of cells for uranium precipitation. The precipitated uranyl phosphate remained tightly associated with the cell surface, thus facilitating easy recovery.