Joined: 16 Mar 2004
|Posted: Tue Aug 25, 2009 1:12 pm Post subject: Fungi with ‘Bling’ Make for Powerful Catalysts and Disinfect
|It brings a new meaning to the phrase organic chemistry. Chemists have discovered that fungi can naturally absorb microscopic metal particles into their flesh in a way that could see metallic fungi used as catalysts or disinfectants.
Left: SEM of a gold- Penicillium hybrid after several months of growth. Right: enlargement of the area indicated, showing the hollow character of the hybrid structure
(Image: Angewandte Chemie)
Industrial catalysts often rely on processes that happen on the surface of metals, so tiny nanoparticles of catalyst with large surface-area-to-volume ratios are particularly effective. But such particles are only effective if they are prevented from clumping together using a chemical solution, which makes it difficult to separate the catalyst from the products of a reaction.
Now Alexander Eychmüller's team at the Dresden University of Technology in Germany has discovered that fungi can assimilate and stabilise nanoparticles as they grow. Because the nanoparticles are immobilised on fungal filaments, they can be easily recovered later.
Eychmüller's team fed media containing gold, silver, platinum or palladium nanoparticles to common fungi, including Penicillium .
After two months the researchers examined the fungi under a scanning electron microscope and found that the growing filaments had become coated in a crust of nanoparticles up to 200 nanometres thick. The newly bling fungi seemed unaffected by their metallic coat. One species could even cope with a coating of silver, known to be toxic to microorganisms, and used as a disinfectant in some clothing.
"We've been surprised and impressed by [the fungi's] resilience," says Eychmüller.
Crucially, although the crust is much thicker than the individual nanoparticles, which are 10 to 20 nanometres across, the nanoparticles do not clump together to form larger particles. Since their surfaces are unobstructed, they retain their powerful catalytic properties.
As well as using metal-coated fungi as catalysts, those decorated with silver could be used for their disinfectant properties, says Eychmüller.
He thinks studying how fungi bind to the particles could also help understand why some organisms are prone to accumulating heavy metal pollutants. "There ought to be reasons why a specific nanoparticle 'docks' to a specific fungus," says Eychmüller. "So far not too much is known about interactions on that level."
Journal Reference: http://www3.interscience.wiley.com/journal/121397021/abstract?CRETRY=1&SRETRY=0