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Improving process stability and kinetics of anaerobic biowaste digestion by promoting direct interspecies electron transfer among syntrophic microbial consortia

Applicant Dr. Stefan Dyksma
Subject Area Microbial Ecology and Applied Microbiology
Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Term from 2017 to 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 388261240
 
Final Report Year 2021

Final Report Abstract

Microbial conversion of organic matter to renewable energy in form of methane is a proven and widespread strategy for effective waste management. In such methane-producing environments, electrical connected bacteria and archaea perform direct interspecies electron transfer (DIET) as alternative syntrophic mechanism to interspecies hydrogen or formate transfer. However, fundamental aspects of the microbial ecology concerning DIET and its significance for biogas production are still unclear. The goal of this research was to elucidate the role of direct interspecies electron transfer among syntrophic short-chain fatty acid-oxidizing consortia for the methanation of organic matter. Within this project we contributed to a more widely applicable knowledge about structure-function relationships of syntrophic core communities in mesophilic and thermophilic digesters by integrating molecular tools such as the 16S rRNA approach, metagenomics and -transcriptomics with cultivation-based techniques. A genome-centric metatranscriptomic approach refutes a major role of DIET in the studied systems and rather suggests electron transfer via formate and hydrogen. However, we achieved fundamental new insights into the ecophysiology of syntrophic propionate- and acetate-oxidizing bacteria in bioreactors. Due to unfavourable thermodynamics, the fermentation of propionate and acetate can be considered as bottleneck in anaerobic digestion of organic matter. Metagenome sequencing and enrichment cultivation revealed novel players in the syntrophic turnover of those quantitatively important intermediates. Strikingly, members of the poorly understood candidate phylum Cloacimonetes were identified as integral part of the syntrophic community in mesophilic anaerobic digesters. In thermophilic dry fermentation of biowaste diverse and novel syntrophic acetate-oxidizing bacteria are important for process functioning and overall organic carbon mineralization.

Publications

  • (2019) Candidatus Syntrophosphaera thermopropionivorans: a novel player in syntrophic propionate oxidation during anaerobic digestion. Environ Microbiol Rep 11: 558–570
    Dyksma, S. and Gallert, C.
    (See online at https://doi.org/10.1111/1758-2229.12759)
  • (2020) Syntrophic acetate oxidation replaces acetoclastic methanogenesis during thermophilic digestion of biowaste. Microbiome, 8:105
    Dyksma, S., Jansen, L. and Gallert, C.
    (See online at https://doi.org/10.1186/s40168-020-00862-5)
 
 

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