Microbial Fixation of CO2 to Fuels and Chemicals

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Microbial Metabolism, Physiology & Genetics".

Deadline for manuscript submissions: 30 December 2024 | Viewed by 8409

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Guest Editor
Department of Environmental Engineering, Democritus University of Thrace, Xanthi, Greece
Interests: anaerobic digestion processes; valorization of waste and biomass; design and operation of bioreactors; bioprocess modeling
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Special Issue Information

Dear Colleagues,

Carbon dioxide (CO2) fixation via biological pathways is an emerging field in the concentrated efforts to reduce the emission of greenhouse gases. Gaseous streams rich in CO2 coming from fossil or biogenic carbon sources (e.g., fossil-based power generation units, biogas plants, biomass combustion units, etc.) could be used to convert CO2 into fuels (methane, ethanol) and chemicals (e.g., acetate, succinate, 2,3-butanediol, lactate, acetone) exploiting the capability of organisms to incorporate CO2 into their metabolism. Besides the naturally occurring CO2 fixation via photosynthesis, there are microbial-assisted processes which require a reducing agent (e.g., hydrogen or electrons provided in a bioelectrochemical system). The technical challenges to make these processes sustainable include the efficient supply of the reducing agent, the integration of water electrolysis powered by renewable resources with hydrogen consumption to reduce CO2, improvement of the bioreactors and the bioelectrochemical systems performing CO2 reduction. Moreover, the microbial profile of the communities developed to transform CO2 to valuable chemicals and fuels is a critical parameter in comprehending the fermentation processes taking place. We welcome any contributions on the hot topic of the microbial fixation of CO2 with a significant impact on decreasing greenhouse gases while also serving as a form of energy storage.

Dr. Katerina Stamatelatou
Guest Editor

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Keywords

  • carbon dioxide
  • biofuels
  • chemicals
  • biomanufacturing
  • microbial
  • biological
  • biochemical
  • bioelectrochemical

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Published Papers (5 papers)

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Research

13 pages, 3252 KiB  
Article
Scaling up Trickle Bed Reactor for Gas Fermentation Technology: The Effect of Temperature and Reactor Characteristics on Mass Transfer
by Sambit Dutta, Hariklia N. Gavala and Ioannis V. Skiadas
Fermentation 2024, 10(12), 623; https://doi.org/10.3390/fermentation10120623 - 6 Dec 2024
Viewed by 276
Abstract
The increasing demand for efficient and sustainable industrial processes has accelerated research into green alternatives. Gas fermentation in a trickle bed reactor is a promising technology; however, optimal scaling up is still challenging. A mass transfer model is crucial for identifying bottlenecks and [...] Read more.
The increasing demand for efficient and sustainable industrial processes has accelerated research into green alternatives. Gas fermentation in a trickle bed reactor is a promising technology; however, optimal scaling up is still challenging. A mass transfer model is crucial for identifying bottlenecks and suggesting design improvements to optimize the scale-up of TBR for gas fermentation. This study explores the effects of temperature, reactor dimensions, and packing material size on the volumetric mass transfer coefficient (kLa) in a commercial-scale trickle bed reactor (TBR). Using dynamic mass transfer modeling, the research results highlight that thermophilic conditions (60 °C) significantly enhance kLa and mass transfer rates for H2, CO, and CO2, despite reduced gas solubility at higher temperatures. Additionally, packing material of smaller particles improves kLa by increasing the surface for gas–liquid interaction, while reactor dimensions, particularly volume and diameter, are shown to critically influence kLa. This study provides valuable insights into optimizing TBR design and scale-up, emphasizing the importance of thermophilic conditions, proper packing material selection, and reactor geometry for efficient gas–liquid mass transfer in syngas (a mixture of H2, CO, and CO2) biological conversion. Overall, the findings offer practical guidelines for enhancing the performance of industrial-scale TBR systems. Full article
(This article belongs to the Special Issue Microbial Fixation of CO2 to Fuels and Chemicals)
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19 pages, 5128 KiB  
Article
Comparative Study of Mesophilic Biomethane Production in Ex Situ Trickling Bed and Bubble Reactors
by Apostolos Spyridonidis and Katerina Stamatelatou
Fermentation 2024, 10(11), 554; https://doi.org/10.3390/fermentation10110554 - 30 Oct 2024
Viewed by 608
Abstract
Biomethane production via biogas upgrading is regarded as a future renewable gas, further boosting the biogas economy. Moreover, when upgrading is realized by the biogas CO2 conversion to CH4 using surplus renewable energy, the process of upgrading becomes a renewable energy [...] Read more.
Biomethane production via biogas upgrading is regarded as a future renewable gas, further boosting the biogas economy. Moreover, when upgrading is realized by the biogas CO2 conversion to CH4 using surplus renewable energy, the process of upgrading becomes a renewable energy storage method. This conversion can be carried out via microorganisms, and has attracted scientific attention, especially under thermophilic conditions. In this study, mesophilic conditions were imposed using a previously developed enriched culture. The enriched culture consisted of the hydrogenotrophic Methanobrevibacter (97% of the Archaea species and 60% of the overall population). Biogas upgrading took place in three lab-scale bioreactors: (a) a 1.2 L bubble reactor (BR), (b) a 2 L trickling bed reactor (TBR) filled with plastic supporting material (TBR-P), and (c) a 1.2 L TBR filled with sintered glass balls (TBR-S). The gas fed into the reactors was a mixture of synthetic biogas and hydrogen, with the H2 to biogas CO2 ratio being 3.7:1, lower than the stoichiometric ratio (4:1). Therefore, the feeding gas mixture did not make it possible for the CH4 content in the biomethane to be more than 97%. The results showed that the BR produced biomethane with a CH4 content of 91.15 ± 1.01% under a gas retention time (GRT) of 12.7 h, while the TBR-P operation resulted in a CH4 content of 90.92 ± 2.15% under a GRT of 6 h. The TBR-S operated at a lower GRT (4 h), yielding an effluent gas richer in CH4 (93.08 ± 0.39%). Lowering the GRT further deteriorated the efficiency but did not influence the metabolic pathway, since no trace of volatile fatty acids was detected. These findings are essential indicators of the process stability under mesophilic conditions. Full article
(This article belongs to the Special Issue Microbial Fixation of CO2 to Fuels and Chemicals)
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13 pages, 2905 KiB  
Communication
Demonstrating Pilot-Scale Gas Fermentation for Acetate Production from Biomass-Derived Syngas Streams
by Pedro Acuña López, Stefano Rebecchi, Elodie Vlaeminck, Koen Quataert, Christian Frilund, Jaana Laatikainen-Luntama, Ilkka Hiltunen, Karel De Winter and Wim K. Soetaert
Fermentation 2024, 10(6), 285; https://doi.org/10.3390/fermentation10060285 - 28 May 2024
Viewed by 1929
Abstract
Gas fermentation is gaining attention as a crucial technology for converting gaseous feedstocks into value-added chemicals. Despite numerous efforts over the past decade to investigate these innovative processes at a lab scale, to date, the evaluation of the technologies in relevant industrial environments [...] Read more.
Gas fermentation is gaining attention as a crucial technology for converting gaseous feedstocks into value-added chemicals. Despite numerous efforts over the past decade to investigate these innovative processes at a lab scale, to date, the evaluation of the technologies in relevant industrial environments is scarce. This study examines the fermentative production of acetate from biomass-derived syngas using Moorella thermoacetica. A mobile gas fermentation pilot plant was coupled to a bubbling fluidized-bed gasifier with syngas purification to convert crushed bark-derived syngas. The syngas purification steps included hot filtration, catalytic reforming, and final syngas cleaning. Different latter configurations were evaluated to enable a simplified syngas cleaning configuration for microbial syngas conversion compared to conventional catalytic synthesis. Fermentation tests using ultra-cleaned syngas showed comparable microbial growth (1.3 g/L) and acetate production (22.3 g/L) to the benchmark fermentation of synthetic gases (1.2 g/L of biomass and 25.2 g/L of acetate). Additional fermentation trials on partially purified syngas streams identified H2S and HCN as the primary inhibitory compounds. They also indicated that caustic scrubbing is an adequate and simplified final gas cleaning step to facilitate extended microbial fermentation. Overall, this study shows the potential of gas fermentation to valorize crude gaseous feedstocks, such as industrial off-gases, into platform chemicals. Full article
(This article belongs to the Special Issue Microbial Fixation of CO2 to Fuels and Chemicals)
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18 pages, 8547 KiB  
Article
Mixotrophic Syngas Conversion Enables the Production of meso-2,3-butanediol with Clostridium autoethanogenum
by Anne Oppelt, Anton Rückel, Markus Rupp and Dirk Weuster-Botz
Fermentation 2024, 10(2), 102; https://doi.org/10.3390/fermentation10020102 - 8 Feb 2024
Cited by 1 | Viewed by 2572
Abstract
Providing simultaneously autotrophic and heterotrophic carbon sources is a promising strategy to overcome the limits of autotrophic syngas fermentations. D-xylose and L-arabinose are particularly interesting as they can be obtained by the hydrolysis of lignocellulosic biomass. The individual conversion of varying initial concentrations [...] Read more.
Providing simultaneously autotrophic and heterotrophic carbon sources is a promising strategy to overcome the limits of autotrophic syngas fermentations. D-xylose and L-arabinose are particularly interesting as they can be obtained by the hydrolysis of lignocellulosic biomass. The individual conversion of varying initial concentrations of these pentoses and D-fructose as reference was studied with C. autoethanogenum in fully controlled stirred-tank reactors with a continuous syngas supply. All mixotrophic batch processes showed increased biomass and product formation compared to an autotrophic reference process. Simultaneous CO and D-xylose or L-arabinose conversion was observed in contrast to D-fructose. In the mixotrophic batch processes with L-arabinose or D-xylose, the simultaneous CO and sugar conversion resulted in high final alcohol-to-acid ratios of up to 58 g g−1. L-arabinose was superior as a mixotrophic carbon source because biomass and alcohol concentrations (ethanol and 2,3-butanediol) were highest, and significant amounts of meso-2,3-butanediol (>1 g L−1) in addition to D-2,3-butanediol (>2 g L−1) were solely produced with L-arabinose. Furthermore, C. autoethanogenum could not produce meso-2,3 butanediol under purely heterotrophic conditions. The mixotrophic production of meso-2,3-butanediol from L-arabinose and syngas, both available from residual lignocellulosic biomass, is very promising for use as a monomer for bio-based polyurethanes or as an antiseptic agent. Full article
(This article belongs to the Special Issue Microbial Fixation of CO2 to Fuels and Chemicals)
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16 pages, 3351 KiB  
Article
Microbial Electrosynthesis Using 3D Bioprinting of Sporomusa ovata on Copper, Stainless-Steel, and Titanium Cathodes for CO2 Reduction
by Suman Bajracharya, Adolf Krige, Leonidas Matsakas, Ulrika Rova and Paul Christakopoulos
Fermentation 2024, 10(1), 34; https://doi.org/10.3390/fermentation10010034 - 30 Dec 2023
Cited by 5 | Viewed by 1954
Abstract
Acetate can be produced from carbon dioxide (CO2) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H2). However, the low solubility of H2 can limit the process. Using metal [...] Read more.
Acetate can be produced from carbon dioxide (CO2) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H2). However, the low solubility of H2 can limit the process. Using metal cathodes to generate H2 at a high rate can improve MES. Immobilizing bacteria on the metal cathode can further proliferate the H2 availability to the bacteria. In this study, we investigated the performances of 3D bioprinting of Sporomusa ovata on three metal meshes—copper (Cu), stainless steel (SS), and titanium (Ti), when used individually as a cathode in MES. Bacterial cells were immobilized on the metal using a 3D bioprinter with alginate hydrogel ink. The bioprinted Ti mesh exhibited higher acetate production (53 ± 19 g/m2/d) at −0.8 V vs. Ag/AgCl as compared to other metal cathodes. More than 9 g/L of acetate was achieved with bioprinted Ti, and the least amount was obtained with bioprinted Cu. Although all three metals are known for catalyzing H2 evolution, the lower biocompatibility and chemical stability of Cu hampered its performance. Stable and biocompatible Ti supported the bioprinted S. ovata effectively. Bioprinting of synthetic biofilm on H2-evolving metal cathodes can provide high-performing and robust biocathodes for further application of MES. Full article
(This article belongs to the Special Issue Microbial Fixation of CO2 to Fuels and Chemicals)
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