Fungi for the bioremediation of soils contaminated by hydrocarbons

Fungi for the bioremediation of soils contaminated by hydrocarbons

An academic study determined the potential of a particular group of these microorganisms to clean up soils contaminated with oil and its derivatives. They discuss their possibilities and alternatives for the future.

Accidental oil spills and their derivatives represent a serious environmental problem, as they are highly polluting and naturally degrade very slowly. For this reason, bioremediation research is becoming increasingly important, which seeks to remove hydrocarbons from the soil in less time, with little impact and at low cost. In these techniques certain bacteria and fungi are used that partially meet the three requirements. In this sense, there is scientific evidence that suggests that bioremediation would be even more efficient if it were based on a particular group of fungi called ‘dark septates’.

A study by the Faculty of Agronomy of the UBA (FAUBA) was able to isolate dark septate fungi (HSO) from the roots of plants that grew in soil contaminated with hydrocarbons in a refinery in Campana, province of Buenos Aires. After conducting a series of laboratory experiments, the researchers concluded that several of the isolated HSOs would have great potential asmicroremediators. The reasons are two: they can transform hydrocarbons into easily degradable compounds and they are able to feed on them.

“We started working with dark septate fungi, which is a group of fungi whose biology is largely unknown. Being filamentous, these fungi grow and spread rapidly, which makes them an interesting alternative as remedies for areas that suffer from this type of contamination, ”said Viviana Chiocchio, professor of the Department of Agricultural Microbiology at FAUBA, adding that the Soils with hydrocarbons are very stressful for microorganisms in general, and that HSOs, in particular, find protection in the roots of the plants that grow there.

“In a Campana refinery we collected plants of 18 different species in an area where a spill had occurred, and we isolated 11 different types from their roots —omorphotypes- of dark septate fungi. With these we carry out experiments in the laboratory, growing them in a culture medium with motor oil as hydrocarbon. The first result that we highlight is that the HSOs were able to make a first ‘attack’ on the oil, leaving it more available for other soil microorganisms to continue degrading it, ”said Chiocchio.

As a second key result, the researcher highlighted that the HSOs were able to feed on the oil. “Chemically, motor oil - like all hydrocarbons - has carbon. Our experiments showed that dark septate fungi consumed carbon from the oil and used it to grow up to 0.57 mm / day. Even though this speed is not very high, the result indicates that these fungi have an important micro-remedial potential ”. Chiocchio presented these advances in a public seminar at the Institute for Research in Agricultural and Environmental Biosciences (FAUBA-Conicet), where he works.

Different approaches

In relation to current ways of bioremedy, Viviana Chiocchio pointed out that various techniques can be used. “Some are based on adding nutrients to stimulate the growth of microorganisms that live in the soil with hydrocarbons, whether they are bacteria or fungi. Others, in inoculating the soil directly with these microorganisms. Personally, my ambition is one day to generate a new technique that does not add nutrients or microorganisms ”.

The researcher explained to Sobre La Tierra that the ability they detected in the HSOs to attack the oil and make it available to other microorganisms was due to a chemical compound that the HSOs produce and release into the environment. This compound, calledsurfactant, makes oil molecules more soluble in water, which makes them easily degradable in a humid environment such as soil.

“If that surfactant compound could be synthesized in the laboratory, it could be applied to the soil directly; you won't even need to inoculate the HSO. This addition of surfactant would be the beginning of the bioremediation process; later, other microorganisms would be in charge of degrading the hydrocarbons. But they are questions that we will investigate in the long term. For now, we continue working to determine the genus and species of the HSOs that performed best in our study, ”Chiocchio concluded.

Video: Bioremediation of Gasoline Contaminated Soil (October 2020).