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Biotechnology Unzipped:
Promises and Realities
(1997) Joseph Henry Press (JHP) The views expressed in this book are solely those of the author(s) and do not necessarily reflect the views of the National Academies. |
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makes it feasible to process low-grade ores containing as little as 0.02 ounces of gold per ton.
Such methods of using microbes in gold mining have already been patented, but are still being developed and are not yet in use on a large scale. Here's how it happens. Just like feeding time at the zoo, a solution of cyanide-producing microbes is let loose in a holding tank with a slurry of finely pulverized gold ore. As soon as the ore comes in contact with the cyanide produced by the microbes, the gold in the ore oxidizes to form a gold-cyanide complex. The soluble gold is then absorbed by the microbe cells—an automatic chemical process that occurs even if the microbes are dead.
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Cells keep working after they're dead Researchers in the United States have developed a way of using non-living bacteria to decontaminate water polluted by uranium. The bacterial cells, which have an affinity for uranium, are mixed in a polymer to form plastic-like ''biobeads." The biobeads are packed into glass tubes and the contaminated water is pumped through them. Any uranium in the water, even in very low concentrations, binds to the biobeads, making the water flowing out of the tubes clean. Technicians are now working on ways to recover the attached uranium and reuse the biobeads. |
Biosorption, as the process is called, can be used on carbon-bearing ores without the need for pretreatment. The microbes have an affinity for the dissolved gold that is much greater than that of the native carbon in the ore itself. The microbes easily outcompete the carbon in the gold-binding race.
Many types of microbes produce cyanide and absorb
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