07 February 2006

Cleaning Up the Environment: Bacteria to the Rescue

In new research from the 1 Feb. issue of Environmental Science and Technology, as described in Physorg.com, microbes have been developed to scavenge metals from spend catalytic converters and electronic scrap disposal, The metal engorged microbes were then used to catalyse and clean industrial waste, converting it to an environmentally friendlier form.

The researchers experimented with the bacteria Desulfovibrio desulfuricans and Escherichia coli. Prior studies revealed that these bacteria could, in the presence of hydrogen gas or the organic molecule formate, take palladium from solution and deposit it as nanocrystals on their cell surfaces.

Mabbett and her colleagues at bioremediation researcher Lynne Macaskie's lab at the University of Birmingham flowed wastewater from spent catalytic converters and electronic scrap disposal operations past the microbes. The resulting palladium crystals, roughly 50 nanometers wide, were half the size of those generated by conventional industrial means. The bacteria also pulled out aluminum, platinum and silver from the waste as nanocrystals.

The researchers then used these dead nanocrystal-coated bacteria in bioreactors where they flowed industrial waste past loaded with a carcinogenic form of chromium known as chromium-VI. These bioreactors were capable of transforming chromium-VI into the non-carcinogenic chromium-III version that could get extracted out. Mabbett and her colleagues published their findings in the Feb. 1 issue of the journal Environmental Science & Technology.

"This research should definitely impact on the mining and scrap metal industries," Mabbett said. "Instead of just implementing methods to clear up their waste end products, these industries could undertake a two-fold process of 'clean up and manufacture,'" and "both industries could potentially make profit from what was once waste." She estimated it could take five to 10 years for such bacterial nanocrystals to reach the market.

The bacterial nanocrystals continued to work even after operating nonstop for three months, while palladium catalyst generated by conventional means lasted for just one week. To achieve such results, the researchers did first have to enrich the wastewater they gave the bacteria with a palladium solution, but the total amount of palladium used to create the bacterial nanocrystals remained less than that used in the conventional catalyst, Mabbett said.

Even before this latest discovery,microbes have had a growing role in environmental cleanups. Other key processes involved in microbial cleanup are fairly well known and described at the above link.


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