Bioremediation of heavy- and radioactive-metal contaminations from soil and ground water John Hanna

Bioremediation The use of biological agents, such as bacteria, fungi, or green plants, to remove or neutralize contaminants, as in polluted soil or water Break down contaminants into less substances (e.g. Petroleum) Act to accumulate the contaminants so they can be easily removed Chemical reduction of heavy metal ions to insoluble forms

Risk-Benefit relationship between contaminants versus nutrition from the consumption of fish Poly-unsaturated fatty acids (Omega-3) fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) Undisputed heatlh benefits (e.g coronary heart disease Heavy metals (e.g Mercury) Dioxins Polychlorinated biphenyls (PCBs)

Rate of CHD cohort study on risks CHD in relationship consuming fish or fish oil

Bioremediation methods available today to remove heavy metal contamination Used for the removal of Mercury, among other metals such as chromium, cadmium, Zinc and radioactive Uranium from agricultural areas or groundwater reservoirs Naturally-occurring organisms or those that have been engineered to enhance their bioremediation capability (biotechnology) Methods include: bio-bleaching, bio-precipitation, bio-sorption, and bio-accumulation

Bio-bleaching Insoluble Metal + HCN  Metal-CN + H+ The use of bacteria and fungi to remove metals (e.g., Cadmium, Copper, Nickel, and Zinc) from contaminated soil Insoluble metals are solubilized with organic acids (e.g. hydrogen cyanide) produced by the living organism to generate a soluble metal ion Insoluble Metal + HCN  Metal-CN + H+

Bio-precipitation or bio-mineralization bio-precipitation/biomineralization involves the formation of insoluble compounds following the reaction of soluble metal ions with either inorganic phosphate, carbonate, or sulfide that is released from bacteria Selection of bacterial strains capable of enhanced organic ion secretion greatly increases the effectiveness of this method Metal ion + HPO42-  Metal-HPO4 Metal ion + CO32-  Metal-CO3 Metal ion + H2S  Metal-S

Bio-sorption and bio-accumulation The removal of soluble metals from solution by biological material. Process are not limited to live organisms but also dead ones which in addition to bacteria also can be carried out by algae and fungi Examples include: Engineering bacterial cells to express mercury binding protein (MerC) or phytochetalins to enhance the removal of mercury, arsenic, or cadmium

Bioremediation with Plants or plant/fungi combinations Plants inoculated with specialized fungi form structures in the plant root systems known as mycorrhiza. Working together the fungi enhances the ability of the plants to absorb materials from the soil

Bioremediation of Uranium contamination from ground water Uranium is removed by the reduction of Uranium (VI) to insoluble Uranium (IV) Same process can be also used to remove selenium and Cadmium contamination In all cases, the chemical reduction of the contaminant is coupled to the oxidation or an organic compound produced by the organism (e.g. acetate, lactate, pyruvate, glycerol, or ethanol) Process can be greatly enhanced by biotechnological methods

Conclusions Bioremediation offers a safe and effective method to remove contaminants from the environment. The use of bioengineered microorganisms, plants, or bacteria will continue to offer promising alternatives to the scientific community and allow the bioremediation of otherwise uninhabitable areas However, in most cases bioremediation is not 100% effective in removing the contaminants Research is needed to establish the Risk/Benefit relationships for individual contaminants in order to make educated decisions to treat individual cases

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