Salud Argentina , Neuquén, Viernes, 06 de septiembre de 2013 a las 10:21

Yeasts for bioremediation

These organisms were found in acid aquatic environments of Agrio River and Cavihue Lake in Neuquén, Argentina

CONICET/DICYT The team led by Maria Rosa Giraudo de van Brook, principal investigator of CONICET at the Center for Biodiversity and Environment Research (INIBIOMA, CONICET-UNCo), found a type of native yeast from the Patagonian Forest capable of accumulating metal in highly acidified environments.

 

Acid aquatic environments contain high concentration of dissolved metals that turn out to be toxic for plants and animals. Some microorganisms are adapted to this kind of places thanks to their metabolic characteristics. Besides, they present high tolerance to different metals, which makes them perfect candidates to be used in remediation processes of acidic soils contaminated with these substances.

 

Since 2004, Giraudo’s team has analyzed the current biodiversity at the Agrio River and Caviahue Lake. The river originates in the Copahue Volcano and when it reaches the plateau it forms the Cavihue Lake. Agrio River has a unique pH gradient: in its source values range from 0,5 and 1 – extremely acid- and throughout its course, pH increases gradually till it neutralizes (pH 7), approximately 40 km. down river.

 

During the investigation, the team isolated 32 native yeasts. They were grouped into 9 categories, according to their degree of adaptation and tolerance to six metals – cadmium, cobalt, copper, lithium, nickel, zinc-. Furthermore, their capacity to accumulate those metals was measured, explains Diego Libkind, associate investigator of CONICET.

 

The results indicate a clear reduction in metal concentration, which is encouraging because, up to then, acidified environments were not recommended for bioremediation processes.

 

“Since metals do not precipitate in the acid environments, the reduction in metal’s concentrations could be attributed to the capture by yeasts’ biomass. A strain of the species Cryptococcus agrionensis, described by the group, was able to capture 15.8 mg of zinc per gram of biomass. Cryptococcus sp. 2 retained 36,25 mg of nickel and 62, 28 mg of zinc per gram, while Lecythophora sp. was able to remove 67, 11 mg of zinc per gram of yeast”, microbiologist Gabriel Russo, member of the project, enumerates.

 

 

Industrial applications and bioremediation

 

In urban areas, waste accumulation generates the dispersion of a great diversity of compounds which leak into groundwater. Some industrial activities – such as mining industry, tanneries, etc – contaminate the environment with heavy metals like copper, zinc, lead, cadmium, chromium, nickel, mercury, cobalt, silver and gold. Thus, the role of microorganisms is vital in metals biogeochemical cycles and their bioremediation.

 

“These yeasts could be used in treatments for effluents polluted with metals like copper, nickel and zinc, which also have cumulative effect in the environment as they enter the trophic chain and some animals store it”, Gabriel Russo explains. Besides, he adds that “traditional chemical methods are only effective for high concentrations of metals but not for low concentrations. In this way, the use of these yeasts could be a complement to improve the available treatment”.

 

Remediation is based on the use of a chemical or biological degradation processes to eliminate polluting substances that could jeopardize the use of resources such us water for human consumption. An in-depth study of the interaction between microorganisms and metals is crucial to develop clearance or detoxification methods for heavy metals and radionuclide. Radionuclides are chemical elements with unstable configuration that release upon disintegration.

 

“Low-cost bioremediation projects, with high efficiency and designed to treat specific problems are important because they provide society with concrete solutions in local terms for the remediation of the kind of contamination that causes important environmental impact. The consequences are serious not only for the environment but also for society as a whole”, Edgardo Donati, CONICET investigator and expert on bioremediation, comments.

 

Furthermore, this line of research can have other applications such as the use of yeasts in bioleaching processes, where those microorganisms are used to recover metals such as gold and copper.