Biological sol-gel ceramics with specific metal binding capacity

Bacteria in polluted environments are adapted to the toxic compounds present there
and often possess effective detoxification strategies. For this reason they are
very prospective for development of in situ bioremediation processes. In former
experiments a selective binding by cells and spores of Bacillus sphaericus
JG-A12 of U, Cu, Pb, Al and Cd from drain waters of uranium mining wastes was
demonstrated. The strain JG-A12 was recovered from the uranium mining waste pile
"Haberland" near the town of Johanngeorgenstadt. B. sphaericus JG-A12 possesses
a surface layer (S-layer). The latter differs significantly at its N-terminal
domain from all other S-layers studied up to date. Cells, spores and purified
S-layer protein fraction of this strain were used for construction of biological
sol-gel ceramics (biocers). Metal-binding kinetics of cells, spores, purified
S-layer fraction and the corresponding biological ceramics were measured. The
biosorption of uranium and copper by the corresponding biocomposites was strongly
influenced by the way of the biocer preparation The highest metal binding capacity
possess biocers with embedded vegetative cells. Larger amounts of uranium and
copper were accumulated by biocers which were prepared by freeze drying or using
penetration reagents like sorbit. Desorption of the bound metals and regeneration
of the biological ceramics was achieved using aqueous citric acid.