Using photosynthetic microbes to remove toxic metals from water

Professor Alexandre Poulain is standing in his lab. He is showing the camera a small bottle full of green liquid known as purple non-sulphur bacteria

Professor Alexandre Poulain with PhD candidate Daniel Grégoire

Department of Biology

Two researchers from the Department of Biology have discovered an innovative way to clean up mercury pollution in Ontario’s lakes and rivers using microorganisms known as anoxygenic phototrophic bacteria.

Mercury (Hg) is a global pollutant, possibly affecting all living things on the planet, even far from industrial areas. Most of its environmental cycling is complex, making it extremely difficult to predict its fate or improve mercury cleanup. With the recent signing of the Minamata Convention, Canada is now legally responsible for managing its own mercury waste. In this context, Professor Alexandre Poulain and PhD candidate Daniel Grégoire have successfully developed a new, environmentally friendly way to remove potentially toxic Hg species from water. Their approach uses phototrophic microbes naturally found in the environment to provide a low cost and low energy alternative to tailing ponds, the current technique used by the mining industry. Purple non-sulphur bacteria and Heliobacteria use light as a source of energy and are ubiquitously found in terrestrial and aquatic environments where oxygen is absent. Under certain conditions, the unique type of photosynthesis they conduct causes an overproduction of electrons. However, if these colorful microbes do not successfully pass on their excess electrons to other molecules in the environment, they die. Prof. Poulain and his team realized that when the microorganisms pass on their excess electrons to mercury, it forces the mercury to change form from a soluble liquid state into a gaseous state. Once in the form of a gas, special filters can be used to strip the mercury away. By simply supplying these microbes with light and nutrients, Poulain and Grégoire have succeeded in removing up to 80% of mercury from water at the laboratory scale.

Due to the extent of mercury pollution worldwide, this discovery has the potential to reduce the environmental footprint of mining and help improve the health of Canada’s environment. Prof. Poulain and his team are heading down the right path with the creation of their new company, Microbright. In the coming years, they aim to fine-tune their methods so that they can go from processing 1-2 % of waste, to 10-20%, and to one day have the potential to remove other high priority contaminants from water. Currently, they are looking for an industrial partner that will allow them to gain access to polluted sites and to start scaling up their prototypes.

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