Optimization of the use of microorganisms as biocatalysts for the decontamination of treated wood
The main objective of the project is to demonstrate that microorganisms such as lignolytic fungi and soil bacteria, individually or in consortium, are effective biocatalysts for the decontamination of copper/azoles treated wood. The different steps of the project are 1) the precise quantification of azoles and copper in the treated wood as well as the evaluation of the influence of leaching phenomena and of the particle size distribution on these concentrations, 2) the development and optimization of a microcosm allowing the decontamination of these woods by microorganisms, 3) the identification of the molecular actors responsible for these decontamination capacities and 4) the «up-scaling« of the process to develop a decontamination system on a medium scale in bio-reactors. This system will allow to quantify in an integrated manner the decontamination of wood by microorganisms such as the quantity of residual polymers of cellulose, hemicellulose and lignin, which can potentially be further valorized.
The experimental strategy consists in developing an efficient microcosm allowing fungal and bacterial microorganisms to develop alone or in consortium in the presence of copper/azole treated sawdust. These microorganisms have interesting detoxifying properties. These properties will be evaluated by measurements of the quantity of copper desorbed from the wood and the proportion of degraded azoles. Molecular analysis will identify the proteins and molecules involved in these detoxification mechanisms. The objective is to develop a bioreactor system optimized for effective decontamination of these woods.
The results obtained so far validate the initial hypothesis that the selected microorganisms are effective for the detoxification of copper from treated wood. The microcosm has been set up and optimized to allow optimal growth of fungi and bacteria. The development of methods for copper and azoles quantification in wood has been completed. We now have an efficient and robust methodology to follow the evolution of these compounds in the wood material. We have also optimized the resistance capacities of the fungus to copper thanks to sequential acclimatization to increasing concentrations.
The perspectives are now to quantitatively follow the desorption of copper and the degradation of azoles from treated wood and to identify the molecular actors responsible for these activities.
Poster presentation by Kévin Claudien at GDR Bois (Novembre 2019 à Epinal): Biocatalyseurs microbiens pour la détoxication de bois traités.
Each year in France the building industry generates around 1,4 Mt of treated wood waste. Currently no recycling of this biomass is possible due to the toxicity of the compounds used for preservation, mainly alkaline copper quaternary and copper azole formulations. This project aims at identifying and developing a strategy using microorganisms and/or microbial enzymes as biocatalysts to remove toxic preservative compounds from wood waste in order to both (i) limit the impact of these molecules on environment and human health, and (ii) use these tons of wastes as new resource for industrial valorization of wood polymer and copper extraction. The working hypotheses are based on the fact that in natural environment, some fungal strains are highly resistant to fungicides used for wood preservation, and fungi and bacteria, either individually or in consortia of microorganisms, are efficient organisms for complex molecules breakdown and metal sequestration. We will work with the model fungus Phanerochaete chrysosporium since we have already shown that it is able to bypass the toxicity of copper/azole compounds. Moreover, 9 bacterial strains have been isolated from its mycosphere. These bacteria, which naturally cooperate with the fungus in a context of wood degradation and which exhibit interesting features regarding complex molecules and metal detoxification capabilities, will be tested as helper for wood decontamination. Indeed, it has been described many times in the literature that a consortium of microorganisms is more efficient than a single species in bioremediation mainly because of the induction of cryptic enzymatic pathways or complementary actions. The sub-objectives of the project aim at (i) evaluating the fate of copper and azoles in wood according to time after fungicide treatment by mapping the quantity and repartition of the compounds in various wood wastes (from 1 to 15 years after copper/azole treatment), (ii) determining the best conditions (medium, microbial strains, “age” of wood after treatment) for an efficient biological wood decontamination process, by developing a microcosm using a consortium of fungi and bacteria, (iii) identifying and characterizing the microbial enzymes and molecules (ie siderophores) directly involved in the decontamination process and (iiii) validating the upscaling potential of the process by testing the decontamination efficiency of the microorganisms and/or purified or semi-purified molecular actors in bioreactors. This will allow quantifying the remaining polymers and extractives in the decontaminated wood for subsequent chemical valorization. The scientific consortium is composed of molecular biologists, wood chemists and an industrial partner and will provide complementary skills to achieve the objectives. This project will provide fundamental information on the microbial detoxification systems but it will also give a proof of concept showing that microorganisms can be used to decontaminate wood waste. In the future this biological process could be developed at a larger scale to set up a process needed by industrials to valorize their wood wastes.
Madame Mélanie Morel-Rouhier (Interactions Arbres/Micro-organismes)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
UMR IAM Interactions Arbres/Micro-organismes
EA4370 LABORATOIRE D'ETUDES ET DE RECHERCHE SUR LE MATERIAU BOIS (LERMAB)
Fenneteau Bois et compagnie / Mr Pierre Fenneteau
UMR IAM Interactions Arbres/Micro-organismes
Help of the ANR 379,900 euros
Beginning and duration of the scientific project: June 2019 - 36 Months