Poison-Eating Bugs Strike Gold

April 28, 1998

The richness of Australia's unique biodiversity has been highlighted with the discovery by scientists from CSIRO and BacTech Pty Ltd, a Perth-based mining biotechnology firm, of indigenous microbes capable of devouring toxic effluent from gold extraction.

The discovery could also pave the way for a major advance in "clean green" processing of minerals such as gold, copper, nickel and zinc from sulphide ores.

Dr Peter Franzmann and Mr Matthew Stott of CSIRO Land and Water and CSIRO Minerals have identified several new species of native microbes able to break down the thiocyanate formed from the cyanide used to extract gold.

The project is funded by the Western Australian Government through its WA Innovation Support Scheme (WAISS), which fosters small innovative enterprises in the State.

Their discovery has led to the development of a process for cleansing the waste streams from inland gold mines, where clean water is often a scarce and costly commodity. Based on a process used by the Homestake mine in the United States, this system uses uniquely Australian organisms adapted to the local conditions.

"We found these bacteria thriving in the tailings ponds of a gold mine in the Western Australian goldfields," Dr Franzmann explains.

Part of the project is to develop a modified bioreactor to process the mine effluent which better suits the local microbes and the specific degradation process.

"We have put them to work in a new system for purifying the waste water, and so far they have managed to reduce the concentration of toxin in the waste-stream 15-fold," he says.

"If we can fine-tune the process a bit more, it will make the water completely re-usable by mines that bioleach refractory ores prior to cyanide gold extraction. Quality water is scarce in WA's gold-producing regions - and any technology which allows us to recycle it will benefit both the industry and the environment."

Dr Franzmann says the discovery highlights the remarkable range and diversity of Australian lifeforms. These bacteria apparently thrive in toxic, salty environments in which few other aquatic animals and plants can survive.

The metabolic versatility of bacteria, which carry out most of the "environmental services" in cleaning up the contaminants, can be harnessed in engineered situations to degrade and detoxify waste effluents.

"Using molecular biology techniques, Mr Stott has found that these microbes' closest relatives are probably the kinds of bacteria which are found in the depths of the ocean, feeding off the mineral-rich streams from hydrothermal vents in the sea-floor. But these ones are from the surface, and are completely new to science."

Scientists now think Australia harbours a multitude of poison-munching microbes, which could be used to render harmless a wide range of industrial and other forms of pollution, and so protect our rivers, lakes, wetlands and groundwater.

But according to Program Leader Dr Martin Houchin of CSIRO Minerals the technology may deliver an even more significant advance -- a purely biological way to extract minerals, especially gold, from sulphide ores.

"At the moment we can use bacteria to bio-oxidise certain gold ores, to open them up so the gold can be leached out conventionally using cyanide," he says.

"However the potential is there to use bacteria to biologically produce a leaching agent for extracting the gold, resulting in a fully biological process."

The result would not only be a new clean, green way to extract gold but also a process which promises to be cheaper for producers, making Australian gold more internationally competitive.

In this way, the team hopes, Australia's unique biological diversity may help to give our minerals industry both an economic and an environmental edge over the world.
-end-


CSIRO Australia

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