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Ingénierie écologique des communautés microbiennes de méthanisation des déchets ligno-cellulosiques

Abstract : In order to evaluate the possibility of establishing an ecological engineering of microbial processes of anaerobic digestion in bioprocesses, different environmental levers were applied to cellulose digesters. The first lever studied was temperature. The second involved preadaptation of a complex biomass by incubation with simple molecules, before addition of cellulose. The third lever consisted in co-inoculating various exogenous biomasses with anaerobic sludge. The consequences of these levers on metabolic and ecological dynamics of cellulose-degrading anaerobic bioreactors were evaluated. Different physicochemical indicators were used to characterize cellulose degradation (intermediate production, gas production, etc.). Molecular biology tools enabled the characterization of microbial dynamics at the community level (ARISA fingerprinting) or individual level (16S rDNA pyrosequencing ). The use of stable isotopes (13C-labeled cellulose) enabled the accurate tracing of both material flows (13C enriched cellulose intermediates) and microorganisms involved in the cellulose degradation chain (functional microbial groups were identified by "stable isotope probing" technique). Temperature changes showed the significant influence of this parameter on microbial communities, especially Archaea. The asymmetric nature of temperature effect on microbial communities, and the irreversible consequences of incubation in thermophilic conditions were highlighted. These properties open interesting perspectives for the use of temperature shocks to modify biomass properties. A biomass functionalization experiment was performed with simple molecules (propionic acid, butyric acid, glucose and cellobiose). It showed that shaping microbial communities through substrate adaptation was possible. Once in contact with the cellulose, functionalized biomasses generated patterns and structures of degradation communities who unexpectedly formed two categories only. This result suggests that it is possible to direct the equilibrium states of a complex microbial community by functional preadaptation. Finally, co-inoculation experiments highlighted the difficulty of directly exploiting the enzymatic properties of efficient cellulolytic flora. But, they also highlighted the possibility of changing biomass diversity balance in bioprocesses. Thus these experiments suggest that a parameter such as community diversity can be manipulated by bioaugmentation in bioprocesses. This work demonstrates that several tools are available to develop an ecological engineering of bioprocesses, through a new management approach at the microbial ecosystem (and related services) level.
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Submitted on : Wednesday, February 12, 2014 - 1:57:43 PM
Last modification on : Monday, June 21, 2021 - 11:34:02 AM
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  • HAL Id : pastel-00945512, version 1



Olivier Chapleur. Ingénierie écologique des communautés microbiennes de méthanisation des déchets ligno-cellulosiques. Sciences de l'environnement. AgroParisTech, 2012. Français. ⟨NNT : 2012AGPT0046⟩. ⟨pastel-00945512⟩



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