Biosorption of heavy metals by Bacillus sphaericus JG-A12 cells, spores and S-layer protein embedded in sol-gel ceramics

Bacillus sphaericus strain JG-A12 was isolated from the uranium mining waste
pile "Haberland" near the town of Johanngeorgenstadt. Vegetative cells and spores
of this strain accumulate selectively large amounts of U, Cu, Pb, Al and Cd from the
highly polluted drain waters of this uranium waste. Interestingly, the strain
JG-A12 possess a surface layer protein (S-layer) with a novel structure. The ability
of B. sphaericus to interact with heavy metals and its geographic origin make
it a good candidate for preparation of bacteria-based ceramics (biocers) for in
situ bioremediation of uranium mining waste pile waters. Biocers were prepared by
dispersing vegetative cells, spores and purified S-layer protein fraction of B.
sphaericus JG-A12 in aqueous silica nano-sols, gelling and drying. Different types
of ceramics were prepared by using air or freeze drying and adding water soluble
compounds as sorbit. Variations in porosity and structure of the biocers were
examined using scanning electron microscopy. The sorption and desorption of uranium
and copper by these biocomposites were investigated and visualised by EDX analysis.
Highest binding capacity demonstrate biocers with embedded Bacillus cells. For
reusing the biocers sorbed uranium and copper can be completely removed from them
by washing with aqueous citric acid.