Fungus could help clean the environment.
A wood-rot fungus called Phanerochaete chrysosporium might play important roles in cleaning up the environment and in helping researchers develop a nontoxic bleaching process for pulp and paper.
Studies at the Oregon Graduate Institute of Science & Technology (OGI), Beaverton, helped confirm that the fungus can break down 2,4-dichlorophenol (2,4-DCP), a precursor to the defoliant Agent Orange, and dioxins, the unwanted byproducts of incineration processes and chlorine-based pulp bleaching techniques.
The fungus's role in paper processing comes from its ability to degrade lignin, which must be removed from wood in converting it to paper, says Michael Gold, head of OGI's department of chemical and biological sciences. Recently, scientists observed that lignin chemical bonds resemble those in toxic pollutants.
Gold points out that the fungus has a broader "appetite" than bacteria, which are highly specific in their actions. He believes it might be able to degrade more than one pollutant at a time. OGI tests have shown that P. chrysosporium can "eat" a variety of other substances, including straw, creosote, and oil.
Research by Gold and postdoctoral scientist Kadar Valli has identified pivotal metabolic steps taken by the fungus to degrade 2,4-DCP to [CO.sub.2], chloride, and water. Each step, they say, is triggered by a particular fungal enzyme. Two key enzymes are manganese peroxidase (MnP), discovered in Gold's lab in 1984, and lignin peroxidase (LiP), discovered independently at OGI and elsewhere in 1983.
The OGI team also developed the first way to insert DNA back into the fungus. This method, devised by Gold and Margaret Alic, is used in genetic engineering studies to develop improved strains that would permit on-site methods for removing chlorophenols from wastes at pulp-and-paper and chemical industry plants.
OGI is trying to find more enzymes that promote degradation. Other research groups have studied the enzyme lacchase and reported that better results can be obtained if MnP and lacchase work together.
"So far we haven't been able to confirm that," says OGI graduates student Fred Perie. "In our tests, MnP in-vitro degrades 2,4-DCP and so does LiP, but lacchase in-vitro doesn't seem to have any great effect."
The OGI work has shown that MnP and LiP promise excellent degrading actions for many wastes and lignin. But Gold emphasizes that it's still important to understand every step in the process. "We've only gotten part way down the path," he says.
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|Publication:||R & D|
|Date:||Oct 1, 1991|
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