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Davin ME, Thompson RA, Giannone RJ, Mendelson LW, Carper DL, Martin MZ, Martin ME, Engle NL, Tschaplinski TJ, Brown SD, Hettich RL. Clostridium autoethanogenum alters cofactor synthesis, redox metabolism, and lysine-acetylation in response to elevated H 2:CO feedstock ratios for enhancing carbon capture efficiency. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2024; 17:119. [PMID: 39227857 PMCID: PMC11370222 DOI: 10.1186/s13068-024-02554-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/10/2024] [Indexed: 09/05/2024]
Abstract
BACKGROUND Clostridium autoethanogenum is an acetogenic bacterium that autotrophically converts carbon monoxide (CO) and carbon dioxide (CO2) gases into bioproducts and fuels via the Wood-Ljungdahl pathway (WLP). To facilitate overall carbon capture efficiency, the reaction stoichiometry requires supplementation of hydrogen at an increased ratio of H2:CO to maximize CO2 utilization; however, the molecular details and thus the ability to understand the mechanism of this supplementation are largely unknown. RESULTS In order to elucidate the microbial physiology and fermentation where at least 75% of the carbon in ethanol comes from CO2, we established controlled chemostats that facilitated a novel and high (11:1) H2:CO uptake ratio. We compared and contrasted proteomic and metabolomics profiles to replicate continuous stirred tank reactors (CSTRs) at the same growth rate from a lower (5:1) H2:CO condition where ~ 50% of the carbon in ethanol is derived from CO2. Our hypothesis was that major changes would be observed in the hydrogenases and/or redox-related proteins and the WLP to compensate for the elevated hydrogen feed gas. Our analyses did reveal protein abundance differences between the two conditions largely related to reduction-oxidation (redox) pathways and cofactor biosynthesis, but the changes were more minor than we would have expected. While the Wood-Ljungdahl pathway proteins remained consistent across the conditions, other post-translational regulatory processes, such as lysine-acetylation, were observed and appeared to be more important for fine-tuning this carbon metabolism pathway. Metabolomic analyses showed that the increase in H2:CO ratio drives the organism to higher carbon dioxide utilization resulting in lower carbon storages and accumulated fatty acid metabolite levels. CONCLUSIONS This research delves into the intricate dynamics of carbon fixation in C. autoethanogenum, examining the influence of highly elevated H2:CO ratios on metabolic processes and product outcomes. The study underscores the significance of optimizing gas feed composition for enhanced industrial efficiency, shedding light on potential mechanisms, such as post-translational modifications (PTMs), to fine-tune enzymatic activities and improve desired product yields.
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Affiliation(s)
- Megan E Davin
- Bredesen Center for Interdisciplinary Research, Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN, USA
- Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | | | | | | | - Dana L Carper
- Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | | | | | - Nancy L Engle
- Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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Ingelman H, Heffernan JK, Harris A, Brown SD, Shaikh KM, Saqib AY, Pinheiro MJ, de Lima LA, Martinez KR, Gonzalez-Garcia RA, Hawkins G, Daleiden J, Tran L, Zeleznik H, Jensen RO, Reynoso V, Schindel H, Jänes J, Simpson SD, Köpke M, Marcellin E, Valgepea K. Autotrophic adaptive laboratory evolution of the acetogen Clostridium autoethanogenum delivers the gas-fermenting strain LAbrini with superior growth, products, and robustness. N Biotechnol 2024; 83:S1871-6784(24)00023-2. [PMID: 38871051 DOI: 10.1016/j.nbt.2024.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/05/2024] [Accepted: 06/10/2024] [Indexed: 06/15/2024]
Abstract
Microbes able to convert gaseous one-carbon (C1) waste feedstocks are increasingly important to transition to the sustainable production of renewable chemicals and fuels. Acetogens are interesting biocatalysts since gas fermentation using Clostridium autoethanogenum has been commercialised. However, most acetogen strains need complex nutrients, display slow growth, and are not robust for bioreactor fermentations. In this work, we used three different and independent adaptive laboratory evolution (ALE) strategies to evolve the wild-type C. autoethanogenum to grow faster, without yeast extract and to be robust in operating continuous bioreactor cultures. Multiple evolved strains with improved phenotypes were isolated on minimal media with one strain, named "LAbrini", exhibiting superior performance regarding the maximum specific growth rate, product profile, and robustness in continuous cultures. Whole-genome sequencing of the evolved strains identified 25 mutations. Of particular interest are two genes that acquired seven different mutations across the three ALE strategies, potentially as a result of convergent evolution. Reverse genetic engineering of mutations in potentially sporulation-related genes CLAU_3129 (spo0A) and CLAU_1957 recovered all three superior features of our ALE strains through triggering significant proteomic rearrangements. This work provides a robust C. autoethanogenum strain "LAbrini" to accelerate phenotyping and genetic engineering and to better understand acetogen metabolism.
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Affiliation(s)
- Henri Ingelman
- ERA Chair in Gas Fermentation Technologies, Institute of Bioengineering, University of Tartu, 50411 Tartu, Estonia
| | - James K Heffernan
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, 4072 St. Lucia, Australia
| | | | | | | | - Asfand Yar Saqib
- ERA Chair in Gas Fermentation Technologies, Institute of Bioengineering, University of Tartu, 50411 Tartu, Estonia
| | - Marina J Pinheiro
- ERA Chair in Gas Fermentation Technologies, Institute of Bioengineering, University of Tartu, 50411 Tartu, Estonia
| | - Lorena Azevedo de Lima
- ERA Chair in Gas Fermentation Technologies, Institute of Bioengineering, University of Tartu, 50411 Tartu, Estonia
| | - Karen Rodriguez Martinez
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, 4072 St. Lucia, Australia
| | - Ricardo A Gonzalez-Garcia
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, 4072 St. Lucia, Australia
| | | | | | | | | | | | | | | | - Jürgen Jänes
- Institute of Molecular Systems Biology, ETH Zürich, 8049 Zürich, Switzerland
| | | | | | - Esteban Marcellin
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, 4072 St. Lucia, Australia.
| | - Kaspar Valgepea
- ERA Chair in Gas Fermentation Technologies, Institute of Bioengineering, University of Tartu, 50411 Tartu, Estonia.
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Schwarz I, Angelina A, Hambrock P, Weuster-Botz D. Simultaneous Formate and Syngas Conversion Boosts Growth and Product Formation by Clostridium ragsdalei. Molecules 2024; 29:2661. [PMID: 38893534 PMCID: PMC11174074 DOI: 10.3390/molecules29112661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/28/2024] [Accepted: 05/31/2024] [Indexed: 06/21/2024] Open
Abstract
Electrocatalytic CO2 reduction to CO and formate can be coupled to gas fermentation with anaerobic microorganisms. In combination with a competing hydrogen evolution reaction in the cathode in aqueous medium, the in situ, electrocatalytic produced syngas components can be converted by an acetogenic bacterium, such as Clostridium ragsdalei, into acetate, ethanol, and 2,3-butanediol. In order to study the simultaneous conversion of CO, CO2, and formate together with H2 with C. ragsdalei, fed-batch processes were conducted with continuous gassing using a fully controlled stirred tank bioreactor. Formate was added continuously, and various initial CO partial pressures (pCO0) were applied. C. ragsdalei utilized CO as the favored substrate for growth and product formation, but below a partial pressure of 30 mbar CO in the bioreactor, a simultaneous CO2/H2 conversion was observed. Formate supplementation enabled 20-50% higher growth rates independent of the partial pressure of CO and improved the acetate and 2,3-butanediol production. Finally, the reaction conditions were identified, allowing the parallel CO, CO2, formate, and H2 consumption with C. ragsdalei at a limiting CO partial pressure below 30 mbar, pH 5.5, n = 1200 min-1, and T = 32 °C. Thus, improved carbon and electron conversion is possible to establish efficient and sustainable processes with acetogenic bacteria, as shown in the example of C. ragsdalei.
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Affiliation(s)
| | | | | | - Dirk Weuster-Botz
- Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, Boltzmannstr. 15, 85748 Garching, Germany; (I.S.)
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Carrasco Muriel J, Cowie N, Taylor Parkins S, Mansouvar M, Groves T, Nielsen LK. Shu: visualization of high-dimensional biological pathways. Bioinformatics 2024; 40:btae140. [PMID: 38452346 PMCID: PMC10957514 DOI: 10.1093/bioinformatics/btae140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 01/03/2024] [Accepted: 03/06/2024] [Indexed: 03/09/2024] Open
Abstract
SUMMARY Shu is a visualization tool that integrates diverse data types into a metabolic map, with a focus on supporting multiple conditions and visualizing distributions. The goal is to provide a unified platform for handling the growing volume of multi-omics data, leveraging the metabolic maps developed by the metabolic modeling community. In addition, shu offers a streamlined python API, based on the Grammar of Graphics, for easy integration with data pipelines. AVAILABILITY AND IMPLEMENTATION Freely available at https://github.com/biosustain/shu under MIT/Apache 2.0 license. Binaries are available in the release page of the repository and the web application is deployed at https://biosustain.github.io/shu.
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Affiliation(s)
- Jorge Carrasco Muriel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Nicholas Cowie
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Shannara Taylor Parkins
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Marjan Mansouvar
- Department of Biotechnology and Biomedicine, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Teddy Groves
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Lars Keld Nielsen
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St Lucia, QLD 4067, Australia
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Orsi E, Nikel PI, Nielsen LK, Donati S. Synergistic investigation of natural and synthetic C1-trophic microorganisms to foster a circular carbon economy. Nat Commun 2023; 14:6673. [PMID: 37865689 PMCID: PMC10590403 DOI: 10.1038/s41467-023-42166-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 10/02/2023] [Indexed: 10/23/2023] Open
Abstract
A true circular carbon economy must upgrade waste greenhouse gases. C1-based biomanufacturing is an attractive solution, in which one carbon (C1) molecules (e.g. CO2, formate, methanol, etc.) are converted by microbial cell factories into value-added goods (i.e. food, feed, and chemicals). To render C1-based biomanufacturing cost-competitive, we must adapt microbial metabolism to perform chemical conversions at high rates and yields. To this end, the biotechnology community has undertaken two (seemingly opposing) paths: optimizing natural C1-trophic microorganisms versus engineering synthetic C1-assimilation de novo in model microorganisms. Here, we pose how these approaches can instead create synergies for strengthening the competitiveness of C1-based biomanufacturing as a whole.
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Affiliation(s)
- Enrico Orsi
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Pablo Ivan Nikel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Lars Keld Nielsen
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
- Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, 4072, Brisbane, QLD, Australia
| | - Stefano Donati
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
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Caivano A, van Winden W, Dragone G, Mussatto SI. Enzyme-constrained metabolic model and in silico metabolic engineering of Clostridium ljungdahlii for the development of sustainable production processes. Comput Struct Biotechnol J 2023; 21:4634-4646. [PMID: 37790242 PMCID: PMC10543971 DOI: 10.1016/j.csbj.2023.09.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 09/13/2023] [Accepted: 09/13/2023] [Indexed: 10/05/2023] Open
Abstract
Constraint-based genome-scale models (GEMs) of microorganisms provide a powerful tool for predicting and analyzing microbial phenotypes as well as for understanding how these are affected by genetic and environmental perturbations. Recently, MATLAB and Python-based tools have been developed to incorporate enzymatic constraints into GEMs. These constraints enhance phenotype predictions by accounting for the enzyme cost of catalyzed model´s reactions, thereby reducing the space of possible metabolic flux distributions. In this study, enzymatic constraints were added to an existing GEM of Clostridium ljungdahlii, a model acetogenic bacterium, by including its enzyme turnover numbers (kcats) and molecular masses, using the Python-based AutoPACMEN approach. When compared to the metabolic model iHN637, the enzyme cost-constrained model (ec_iHN637) obtained in our study showed an improved predictive ability of growth rate and product profile. The model ec_iHN637 was then employed to perform in silico metabolic engineering of C. ljungdahlii, by using the OptKnock computational framework to identify knockouts to enhance the production of desired fermentation products. The in silico metabolic engineering was geared towards increasing the production of fermentation products by C. ljungdahlii, with a focus on the utilization of synthesis gas and CO2. This resulted in different engineering strategies for overproduction of valuable metabolites under different feeding conditions, without redundant knockouts for different products. Importantly, the results of the in silico engineering results indicated that the mixotrophic growth of C. ljungdahlii is a promising approach to coupling improved cell growth and acetate and ethanol productivity with net CO2 fixation.
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Affiliation(s)
- Antonio Caivano
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Building 223, 2800, Kongens Lyngby, Denmark
| | - Wouter van Winden
- DSM-Firmenich Science & Research - Bioprocess Innovation, Rosalind Franklin Biotechnology Center, Alexander Fleminglaan 1, 2613 AX, Delft, the Netherlands
| | - Giuliano Dragone
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Building 223, 2800, Kongens Lyngby, Denmark
| | - Solange I. Mussatto
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Building 223, 2800, Kongens Lyngby, Denmark
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7
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Nwaokorie UJ, Reinmets K, de Lima LA, Pawar PR, Shaikh KM, Harris A, Köpke M, Valgepea K. Deletion of genes linked to the C 1-fixing gene cluster affects growth, by-products, and proteome of Clostridium autoethanogenum. Front Bioeng Biotechnol 2023; 11:1167892. [PMID: 37265994 PMCID: PMC10230548 DOI: 10.3389/fbioe.2023.1167892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 05/03/2023] [Indexed: 06/03/2023] Open
Abstract
Gas fermentation has emerged as a sustainable route to produce fuels and chemicals by recycling inexpensive one-carbon (C1) feedstocks from gaseous and solid waste using gas-fermenting microbes. Currently, acetogens that utilise the Wood-Ljungdahl pathway to convert carbon oxides (CO and CO2) into valuable products are the most advanced biocatalysts for gas fermentation. However, our understanding of the functionalities of the genes involved in the C1-fixing gene cluster and its closely-linked genes is incomplete. Here, we investigate the role of two genes with unclear functions-hypothetical protein (hp; LABRINI_07945) and CooT nickel binding protein (nbp; LABRINI_07950)-directly adjacent and expressed at similar levels to the C1-fixing gene cluster in the gas-fermenting model-acetogen Clostridium autoethanogenum. Targeted deletion of either the hp or nbp gene using CRISPR/nCas9, and phenotypic characterisation in heterotrophic and autotrophic batch and autotrophic bioreactor continuous cultures revealed significant growth defects and altered by-product profiles for both ∆hp and ∆nbp strains. Variable effects of gene deletion on autotrophic batch growth on rich or minimal media suggest that both genes affect the utilisation of complex nutrients. Autotrophic chemostat cultures showed lower acetate and ethanol production rates and higher carbon flux to CO2 and biomass for both deletion strains. Additionally, proteome analysis revealed that disruption of either gene affects the expression of proteins of the C1-fixing gene cluster and ethanol synthesis pathways. Our work contributes to a better understanding of genotype-phenotype relationships in acetogens and offers engineering targets to improve carbon fixation efficiency in gas fermentation.
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Affiliation(s)
- Ugochi Jennifer Nwaokorie
- ERA Chair in Gas Fermentation Technologies, Institute of Technology, University of Tartu, Tartu, Estonia
| | - Kristina Reinmets
- ERA Chair in Gas Fermentation Technologies, Institute of Technology, University of Tartu, Tartu, Estonia
| | - Lorena Azevedo de Lima
- ERA Chair in Gas Fermentation Technologies, Institute of Technology, University of Tartu, Tartu, Estonia
| | - Pratik Rajendra Pawar
- ERA Chair in Gas Fermentation Technologies, Institute of Technology, University of Tartu, Tartu, Estonia
| | | | | | | | - Kaspar Valgepea
- ERA Chair in Gas Fermentation Technologies, Institute of Technology, University of Tartu, Tartu, Estonia
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8
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Allaart MT, Diender M, Sousa DZ, Kleerebezem R. Overflow metabolism at the thermodynamic limit of life: How carboxydotrophic acetogens mitigate carbon monoxide toxicity. Microb Biotechnol 2023; 16:697-705. [PMID: 36632026 PMCID: PMC10034630 DOI: 10.1111/1751-7915.14212] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/29/2022] [Accepted: 01/01/2023] [Indexed: 01/13/2023] Open
Abstract
Carboxydotrophic metabolism is gaining interest due to its applications in gas fermentation technology, enabling the conversion of carbon monoxide to fuels and commodities. Acetogenic carboxydotrophs play a central role in current gas fermentation processes. In contrast to other energy-rich microbial substrates, CO is highly toxic, which makes it a challenging substrate to utilize. Instantaneous scavenging of CO upon entering the cell is required to mitigate its toxicity. Experiments conducted with Clostridium autoethanogenum at different biomass-specific growth rates show that elevated ethanol production occurs at increasing growth rates. The increased allocation of electrons towards ethanol at higher growth rates strongly suggests that C. autoethanogenum employs a form of overflow metabolism to cope with high dissolved CO concentrations. We argue that this overflow branch enables acetogens to efficiently use CO at highly variable substrate influxes by increasing the conversion rate almost instantaneously when required to remove toxic substrate and promote growth. In this perspective, we will address the case study of C. autoethanogenum grown solely on CO and syngas mixtures to assess how it employs acetate reduction to ethanol as a form of overflow metabolism.
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Affiliation(s)
| | - Martijn Diender
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Robbert Kleerebezem
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
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9
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Genome-wide CRISPRi screen identifies enhanced autolithotrophic phenotypes in acetogenic bacterium Eubacterium limosum. Proc Natl Acad Sci U S A 2023; 120:e2216244120. [PMID: 36716373 PMCID: PMC9963998 DOI: 10.1073/pnas.2216244120] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Acetogenic bacteria are a unique biocatalyst that highly promises to develop the sustainable bioconversion of carbon oxides (e.g., CO and CO2) into multicarbon biochemicals. Genotype-phenotype relationships are important for engineering their metabolic capability to enhance their biocatalytic performance; however, systemic investigation on the fitness contribution of individual gene has been limited. Here, we report genome-scale CRISPR interference screening using 41,939 guide RNAs designed from the E. limosum genome, one of the model acetogenic species, where all genes were targeted for transcriptional suppression. We investigated the fitness contributions of 96% of the total genes identified, revealing the gene fitness and essentiality for heterotrophic and autotrophic metabolisms. Our data show that the Wood-Ljungdahl pathway, membrane regeneration, membrane protein biosynthesis, and butyrate synthesis are essential for autotrophic acetogenesis in E. limosum. Furthermore, we discovered genes that are repression targets that unbiasedly increased autotrophic growth rates fourfold and acetoin production 1.5-fold compared to the wild-type strain under CO2-H2 conditions. These results provide insight for understanding acetogenic metabolism and genome engineering in acetogenic bacteria.
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10
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Schulz S, Molitor B, Angenent LT. Acetate augmentation boosts the ethanol production rate and specificity by Clostridium ljungdahlii during gas fermentation with pure carbon monoxide. BIORESOURCE TECHNOLOGY 2023; 369:128387. [PMID: 36435417 DOI: 10.1016/j.biortech.2022.128387] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 11/20/2022] [Accepted: 11/21/2022] [Indexed: 06/16/2023]
Abstract
Recycling waste gases from industry is vital for the transition toward a circular economy. The model microbe Clostridium ljungdahlii reduces carbon from syngas and primarily produces acetate and ethanol. Here, a gas fermentation experiment is presented in chemostats with C. ljungdahlii and pure carbon monoxide (CO) as feedstock while entirely omitting yeast extract. A maximum ethanol production rate of 0.07 ± 0.01 g L-1 h-1 and a maximum average ethanol/acetate ratio of 1.41 ± 0.39 was observed under steady-state conditions. This confirmed that CO as the sole feedstock pushes the metabolism toward more reduced fermentation products. This effect was even more pronounced when 15 mM sodium acetate was added to the feed medium. An ethanol production rate of 0.23 ± 0.01 g L-1 h-1 was achieved, representing an increase of more than 240%. This increase was accompanied by an increase in cell density and selectivity toward ethanol, with a maximum average ethanol/acetate ratio of 92.96 ± 28.39. Oxygen contaminations voided this effect, although the cultures were still able to maintain a stable biomass concentration and ethanol production rate. These findings highlight the potential of CO-fermentation with acetate augmentation and the importance of preventing oxygen contaminations.
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Affiliation(s)
- Sarah Schulz
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany
| | - Bastian Molitor
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany; Cluster of Excellence - Controlling Microbes to Fight Infections, University of Tübingen, Germany
| | - Largus T Angenent
- Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany; Cluster of Excellence - Controlling Microbes to Fight Infections, University of Tübingen, Germany; AG Angenent, Max Planck Institute for Biology Tübingen, Max Planck Ring 5, 72076 Tübingen, Germany; Department of Biological and Chemical Engineering, Aarhus University, Universitetsbyen 36, 8000 Aarhus C, Denmark; The Novo Nordisk Foundation CO(2) Research Center (CORC), Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
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