A functional material that combines the Cr(VI) reduction activity of Burkholderia sp. with the adsorbent capacity of sol-gel materials

In the present work, Cr(VI) reduction in aqueous as well as in soil environments has been studied using free and sol-gel immobilized Burkholderia sp. Enhanced reduction rates were achieved by immobilized cells, which are found to be protected from the deleterious effects of high Cr(VI) concentrations. Immobilized bacteria showed enhanced performance in comparison with free cells because of the combination of bacteria biotransformation effect and chromium adsorption on silica matrices. Moreover, bacteria did not lose any activity after four cycles of reutilization. Bacteria immobilized in silica matrices had the ability to completely reduce 100 mu g ml(-1) Cr(VI) after 4 days of incubation in aqueous media and to transform 200 mu g ml(-1) Cr(VI) after 7 days in sterile soil. Immobilized bacteria demonstrated highly efficient Cr(VI) reduction over the Cr(VI) concentration range 50-500 mu g g(-1) and 200-800 mu g g(-1) in aqueous and soil environments, respectively. These results highlight the potential of this functional material that combines the biological activity of bacterial cells with the adsorbent capacity of sol-gel materials.