Can surfactants increase the microbiological degradation of oils in North Sea waters? An international research team from the universities of Stuttgart and Tübingen, together with China West Normal University and the University of Georgia, have explored this question and the results reveal the potential for a more efficient and environmentally friendly response to the oil spill.
It is estimated that oil spills into the oceans is about 1,500 million liters per year globally. This leads to significant environmental pollution globally, as the oil contains dangerous compounds such as polycyclic aromatic hydrocarbons that can have toxic or mutagenic effects on organisms. Oil spills, particularly catastrophic ones that quickly release large amounts of oil into the ocean, such as tanker accidents or accidents on oil drilling platforms such as Deepwater Horizon in 2010, are particularly devastating.
In these oil spills, large amounts of chemical dispersants, ranging in the millions of liters depending on the amount of oil, are routinely used to dissolve oil slicks, prevent oil from reaching shorelines, and enhance dispersion of oil in water. It is hoped that this will enhance the degradation of the microbial oils. This is because the special microorganisms prevalent in nature can feed on the components of crude oil and break them down into harmless substances. This special ability of microbes naturally cleans areas contaminated with oil.
“In a study from the USA published in 2015, we showed – contrary to expectations – that chemical dispersants in deep-sea waters from the Gulf of Mexico can slow the decomposition of microbial oils,” says Professor Sarah Kleindienst, who worked at the University of Tübingen until 2022 and now works at the University of Stuttgart. “Since then, the topic has been at the center of contentious discussions, and there is still no simple answer as to how to combat the oil spill more effectively,” emphasizes Professor Sarah Kleindienst.
In the search for more environmentally friendly ways to deal with oil spills, surfactants could offer a promising alternative to chemical dispersants. Surfactants are produced by microorganisms and can increase the bioavailability of oil components. This can thus promote microbial oil decomposition, which is critical for purification.
Seawater experiments from the North Sea
An international research team led by environmental microbiologist Professor Sarah Kleindienst, with Professor Andreas Kappler (University of Tübingen) and biogeochemist Professor Samantha Joy (University of Georgia), compared the effects of biotic agents and chemical dispersants. In the laboratory at the University of Tübingen, the researchers simulated the conditions of an oil spill. In their experiment, they took more than 100 liters of surface water from the North Sea near the island of Helgoland. Seawater was treated with either a bio-dispersive rhamnolipid (either Corexit 9500 or Slickgone NS), in the presence and absence of oil. The research team used radioactive markers to track the degradation of the oil by microorganisms in detail. “Our investigations with radioactively labeled hydrocarbons or a radioactive amino acid showed that the highest rates of microbial hydrocarbon oxidation and protein synthesis occurred in rhamnolipid-treated oily microorganisms,” says Professor Lu Lu, who previously worked at the University of Tübingen and now works at China West Normal University.
The effect on the composition of microbial communities also differed significantly between methods using surfactants compared to chemical dispersants. “This result indicates that the use of biosurfactants may stimulate different microbial oil degradation factors, in terms of growth and activity, which in turn can affect the cleanup process after oil spills,” says Professor Lu Lu.
Professor Sarah Kleindienst adds: “Our findings indicate that surfactants have great potential for use in future oil spills in the North Sea or similar nutrient-rich ocean habitats.” “Continuing our vision for our business is to develop bio-agent-based products that offer effective and environmentally friendly methods of combating oil spills.”