[hal-04926148] Converting biowaste into biomolecules using saline and non-saline microbial electrolyzers
Microbial electrolysis cells (MECs) are promising technologies for the production of multi-carbon compounds by electrotrophic microorganisms at the cathode, using energy and carbon extracted from organic waste by electrogenic microorganisms at the anode. The nature of the products formed depends on the taxonomic composition of the microbial community. This study examines the impact of electrolyte salinity on the microbial assembly of electroactive consortia. Salinity is a key performance parameter in bioelectrochemical systems, as it helps reduce internal resistance and optimize energy efficiency. The study compares hypersaline reactors developed from inocula collected from salt marshes with a non-saline reference system using sludge from an industrial digester (Desmond-Le Quéméner et al., 2019). Both types of reactors are operated in triplicates, each combining a bioanode with a homoacetogenic biocathode obtained by heat treatment of the inocula to eliminate methanogenic archaea. An intermediate compartment, separated by ion-exchange membranes, is integrated to extract and concentrate carboxylates formed at the cathode via electrodialysis. Different electrode configurations are used: a flat anode to maximize electrocatalytic activity and a granular cathode to increase the exchange surface between electrons and the microbial community. These design elements allow for the selection and adaptation of specific communities in each compartment. Initial tests with different types of saline electrolytes revealed the impact of salt composition on the catalytic performance of microbial electrolysis reactors. Reactors operated with NaCl-based salt solutions showed promising results in terms of energy efficiency, with high current density measurements. The production of carboxylates at the cathode by both types of microbial communities was demonstrated, providing a technological proof of concept for the proper functioning of the electrolysis cells. Ribotag sequencing analyses of 16S rDNA and rRNA are used to describe the adaptation process of microbial consortia to specific electrode configurations and the structuring of taxonomic and functional assemblages from the same initial community under saline and non-saline conditions. Reference: Desmond-Le Quéméner, E., Bridier, A., Tian, J.-H., Madigou, C., Bureau, C., Qi, Y., & Bouchez, T. (2019). Biorefinery for heterogeneous organic waste using microbial electrochemical technology. Bioresource Technology, 292, 121943. https://doi.org/10.1016/j.biortech.2019.121943
ano.nymous@ccsd.cnrs.fr.invalid (Louise Rigaud) 03 Feb 2025
https://hal.inrae.fr/hal-04926148v1
[hal-04715274] Harnessing Lignocellulolytic and Electrogenic Potential: Insights from Shewanella oneidensis MR-1 and Cellulomonas Strains on Lignocellulosic Biomass
The biodegradable and renewable nature of lignocellulosic biomass (LCB) has gained significant interest in recent years. This study explores the lignocellulolytic and electrogenic potential of Shewanella oneidensis MR-1, Cellulomonas fimi ATCC 484, and Cellulomonas biazotea NBRC 12680 on LCB. Two strategies were tested: assessing strains LCB degradation ability under non-electrochemical and electrochemical conditions. Strain selection was based on literature, and bioinformatical analyses were conducted to predict CAZymes and carbohydrate degradation pathways. Cellulomonas strains have a potential to degrade LCB due to high CAZyme count and specific metabolic pathways. Strains growth capacity on LCB was evaluated by culturing without electrodes on LCB for 12 days, showing superior growth on wheat bran compared to wheat straw. Enzymatic assays indicate laccase activity in all strains, highest in C. biazotea NBRC 12680 (11.66 IU). The strains ability to form electrogenic biofilms on carbon cloth anodes polarized at +0.2 V (vs Ag/AgCl) was evaluated. The results indicate that bioanodes can function with wheat bran (max current density: 14.92 mA m −2 ), with voltammograms showing redox activities. Attenuated total reflection Fourier transform infrared spectroscopy shows lignin and protein degradation in both electrochemical and non-electrochemical experiments. These findings suggest potential use of these strains in electro-microbial systems with LCB.
ano.nymous@ccsd.cnrs.fr.invalid (Animut Assefa Molla) 30 Sep 2024
https://hal.science/hal-04715274v1
[hal-04462025] Selection, adaptation and characterization of electrosynthetic microbial communities
In the context of the energy transition, the use of organic waste in environmental biorefineries is an attractive option due to its low cost and potential to replace fossil fuels. However, this approach presents technological challenges due to the heterogeneity and variability over time of organic waste, increasing the complexity of purification treatments for the molecules of interest and resulting in higher final costs. Microbial electrochemical technologies are emerging as promising solutions to overcome these problems, by allowing the physical separation of oxidation from contaminated waste streams used as raw materials (bioanode) from the synthesis of bio-based chemical molecules (biocathode). Recent scientific studies have focused on the production of methane and acetic acid at the cathode, associated with the electrolysis of water at the anode (abiotic). The objective of this study is to combine a bioanode with a biocathode, in order to reduce carbon dioxide to carboxylates, by the selection of homoacetogenic bacterial communities, at the cathode. The electrons generated at the anode, by oxidation of the organic matter by electrogenic microorganisms, are transferred to the cathode, for the reduction of carbon dioxide into multicarbon molecules by electrotrophic microorganisms. In addition to the two main compartments, an intermediate compartment, isolated by ion exchange membranes, is integrated in order to extract and concentrate the carboxylates produced in a sterile solution. This research aims to explore the diversity of carboxylates produced at the biocathode as a function of the selection and dispersion conditions of the microbial assembly. Both compartments are inoculated with the same mixture of biowaste hydrolysate (Tian et al., 2023) and salt marsh sediments, as hypersaline inocula have been identified as particularly suitable for microbial electrochemical applications. These inoculation conditions make it possible to enrich microbial diversity and study the selection process that takes place at the anode and cathode on the same reservoir of diversity. Only the mixture intended for cathode inoculation is heat-treated in order to select homoacetogenic bacterial communities capable of sporulation, from the class Clostridia (Diallo et al., 2021). Anaerobic conditions are ensured by N2 bubbles and the cathode is supplied daily with CO2, which is the only source of external carbon. In addition, the two electrodes have distinct geometrics: the anode is a carbon cloth while the cathode is a carbon brush with granules of the same material. Thus, the same inoculum is subject to different selection processes, including oxidation or reduction capacity, different carbon sources, the ability to form a biofilm and to carry out electron exchanges with a 2D electrode or 3D, etc. The main objective of this first triplicata experiment is to evaluate the efficiency of the use of a hypersaline inoculum, both for the oxidation of organic matter at the anode, and for the reduction of carbon dioxide to carboxylates at the cathode, as well as the efficiency of the extraction of these carboxylate ions in an intermediate compartment. We also want to determine all the carboxylates produced, in order to evaluate the possibility of diversifying or, on the contrary, of specializing the synthesis of these molecules by modifying the microbial assembly through selection and dispersion. Ultimately, this project aims to guide the production of dyes by a model microorganism, froms carboxylates formed in the biocathode and concentrated within the intermediate compartment. These dyes will have specific applications in the textile industry, demonstrating the potential of this innovative approach in the development of sustainable processes for industrial applications. References: Diallo, M., Kengen, S. W. M., & López-Contreras, A. M. (2021). Sporulation in solventogenic and acetogenic clostridia. Applied Microbiology and Biotechnology, 105(9), 3533-3557. https://doi.org/10.1007/s00253-021-11289-9 Tian, J.-H., Lacroix, R., Yaqoob, A. A., Bureau, C., Midoux, C., Desmond-Le Quéméner, E., & Bouchez, T. (2023). Study of a Pilot Scale Microbial Electrosynthesis Reactor for Organic Waste Biorefinery. Energies, 16(2), 591. https://doi.org/10.3390/en16020591
ano.nymous@ccsd.cnrs.fr.invalid (Louise Rigaud) 16 Feb 2024
https://hal.inrae.fr/hal-04462025v1
