Bioaugmentation for the remediation of pesticides polluted agricultural soils: efficiency and side effects – EPURSOL

The research program relies on a proof of concept conducted with selected pesticide-degrading microbial consortia grown as biofilms on selected formulated carrier materials (e.g. raw or modified zeolites) to form biocomposites. EPURSOL will be carried out with microorganisms known to lead to the complete mineralization of MCPA, 2,4-D or glyphosate herbicides that are among the most used in France and Europe, and frequently detected in soils and water resources. These active substances are formulated as ‘contact herbicides’ absorbed by weeds after contact with leaves (i.e. weed post-emergence systemic herbicides). Once in soil the active substance of each of these three foliar herbicides has no interest so that their biodegradation via a bioaugmentation process will not interfere with their agronomical efficiency. The harmlessness, stability and efficiency of such biocomposites in bioaugmentation of soils will be studied at different scales (in a lab to field experimental design, including a demonstration platform). Both the efficiency and potential side effects of this biotechnology will be assessed on abiotic and biotic soil components using the coalescence concept. During the project, the technical choices (carrier materials, strains) will be made with the final goal of field scale applications of this biotechnological solution. EPURSOL will be achieved thanks to the association of partners harbouring complementary expertise in microbiology, molecular biology, material sciences, biotechnology, agronomy and geochemistry.

At the end of the project, the expected results and final products developed are (i) scientific and technological progress on the bioaugmentation technology and its potential impacts on the receiving soil (including knowledge on the coalescence concept and biofilm development on a surface), (ii) efficient formulated biocomposites immediately available for end users, and (iii) a patent on the formulation and way of use of the biocomposites for pesticides-contaminated soils treatment by bioaugmentation approach.

The results of the project will lead to technical and operational evolutions for the design of bioaugmentation technology that will be immediately available for the private partner of the project (GERME S.A.):
- the use of formulated carrier materials, and insights for the formulation of carrier materials (by surface modification) to improve biomass attachment and stability,
- the selection of new microbial consortia able to perform a complete biodegradation of pesticides (MCPA, 2,4 D, glyphosate).
According to the results obtained during the project, a patent on the formulation and the way of use of biocomposite for the treatment of polluted soil by bioaugmentation is expected. A commercial product should be available for farmers, and training sessions and/or meetings mentioned above will favour the technical transfer towards end users. In addition to bioaugmentation for biormediation, such technological progresses will have applications in other fields involving the use of fixed biomass and could thus be transferred to other biotechnological fields: bioaugmentation to improve plant growth and production and/or favour plant immunity, (waste)water treatment in fixed bed reactors…

The results of the EPURSOL project were presented as conference or poster in the following congres :

Sakineh Abbasi, Marion Devers-Lamrani, Fabrice Martin-Laurent, Caroline Michel, Nadine Rouard, Aymé Spor. Assessing the efficiency and the side-effects of atrazine-degrading biocomposites amended to contaminated soil. 3rd International meeting on new strategies in Bioremediation/Restoration processes. 29-30 June, 2023, Muttenz, Switzerland.

Fatima Meite, Alain Seron, Karine Michel, Claude Le Milbeau, Mikael Motelica-Heino, Caroline Michel. Remediation of MCPA contaminated soils using bacterial biofilms on carrier materials (biocomposites): impact of carrier materials and improvements via surface modifications. 7th International Symposium on Environmental Biotechnology and Engineering (7ISEBE), Mai 2023, Marseille, France. ?hal-04053189?.

Caroline Michel, Nataliia Gorodylova, Alain Seron, Karine Michel, Catherine Joulian, et al.. Bioaugmentation for the treatment of pesticides polluted soils: selection of carrier materials for microbial biofilm formation and inoculation in soil. 3rd International Conference on Microbial Ecotoxicology-EcotoxicoMic, Nov 2022, Montpellier, France ?hal-03778412?.

Within the context of Anthropocene, food sustainability has become a major topic together with the preservation of water and soil resources and biodiversity. All around the world, the model of agriculture is mainly based on the use of pesticides that threaten soil and aquatic ecosystems and consequently drinking water quality. In addition, pesticides and their transformation products can have adverse effects on biota and possibly on human health. With the constant development of new molecules, their degradation residues still represent a major threat to natural ecosystems, water resources and human health to be tackled. In the absence of a European and national soil protection Directive, to complete monitoring tasks, a posteriori on site pesticide residues innovative mitigation approaches are of interest and might be implemented. These are all opportunities to be seized to develop sustainable agriculture and guarantee the quality of the environment.
Bioaugmentation to restore pesticides-contaminated soils on site -via the inoculation of polluted environments with degrading-microorganisms- is very promising as it is a cost effective and not perturbing (i.e. no excavation required) green technology. However, to deploy this approach on the market, several scientific and technological barriers are still to be lifted: (i) the improvement of pesticide-degrading inoculants delivery into soil, mainly in terms of viability and biomass, (ii) the selection of the good inoculant expressing the desired pesticide-degrading activity once in soil and allowing the complete pesticides biodegradation, and (iii) the evaluation of possible side effects of bioaugmentation on both abiotic and biotic soil properties.
The EPURSOL project tackles scientific and technological challenges relative to the use of bioaugmentation in cropped arable soils to reduce pesticides concentrations in soil. For this, a cutting-edge bioaugmentation approach based on the formulation of biocomposites is foreseen, taking into account its potential impacts on the biotic and abiotic properties of the receiving soil. EPURSOL relies on a proof of concept using a microbial biofilm-based approach as a way for delivering microorganisms to soil. The project will be conducted with model topical active substances and selected pesticide-degrading microbial consortia grown as biofilms on formulated carrier materials to form biocomposites. One of the major novelties is to operate chemical or physical modifications at the surface of carrier materials to deliver nutrient sources and/or favour biofilm attachment, growth, stability and activity. To ensure a complete biodegradation of pesticides in soil, EPURSOL experiments will be carried out with pure microorganisms and microbial consortia harbouring the pesticide-degrading pathways. By developing a lab-to-field experimental design (lysimeters, mesocosms), EPURSOL will not only evaluate the harmlessness, stability and efficiency of the process developed, but also assess its possible non-intentional effects on soil abiotic (texture, structure, water holding capacity…) and biotic (microbial diversity, C and N microbial functions) properties by monitoring the installation of the inoculant in the indigenous soil microbiota and its ecotoxicological impact. The technical trajectories (carrier material, strains…) and the industrial-scale process for biocomposite production and storage will be made in collaboration with end-users for field scale applications. EPURSOL will be conducted thanks to the association of public and private partners and stakeholders with complementary skills in microbial ecology and ecotoxicology, materials science, biogeosciences, agriculture and biotechnology. This project, in addition to providing an innovative approach to clean agricultural soils from pesticide residues, will revisit and improve the classical bioaugmentation strategy, and provide a breakthrough to implement this technology to Green Deal AgTech.