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Bae J, Park C, Jung H, Jin S, Cho BK. Harnessing acetogenic bacteria for one-carbon valorization toward sustainable chemical production. RSC Chem Biol 2024; 5:812-832. [PMID: 39211478 PMCID: PMC11353040 DOI: 10.1039/d4cb00099d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Accepted: 07/06/2024] [Indexed: 09/04/2024] Open
Abstract
The pressing climate change issues have intensified the need for a rapid transition towards a bio-based circular carbon economy. Harnessing acetogenic bacteria as biocatalysts to convert C1 compounds such as CO2, CO, formate, or methanol into value-added multicarbon chemicals is a promising solution for both carbon capture and utilization, enabling sustainable and green chemical production. Recent advances in the metabolic engineering of acetogens have expanded the range of commodity chemicals and biofuels produced from C1 compounds. However, producing energy-demanding high-value chemicals on an industrial scale from C1 substrates remains challenging because of the inherent energetic limitations of acetogenic bacteria. Therefore, overcoming this hurdle is necessary to scale up the acetogenic C1 conversion process and realize a circular carbon economy. This review overviews the acetogenic bacteria and their potential as sustainable and green chemical production platforms. Recent efforts to address these challenges have focused on enhancing the ATP and redox availability of acetogens to improve their energetics and conversion performances. Furthermore, promising technologies that leverage low-cost, sustainable energy sources such as electricity and light are discussed to improve the sustainability of the overall process. Finally, we review emerging technologies that accelerate the development of high-performance acetogenic bacteria suitable for industrial-scale production and address the economic sustainability of acetogenic C1 conversion. Overall, harnessing acetogenic bacteria for C1 valorization offers a promising route toward sustainable and green chemical production, aligning with the circular economy concept.
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Affiliation(s)
- Jiyun Bae
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
| | - Chanho Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
| | - Hyunwoo Jung
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
| | - Sangrak Jin
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
| | - Byung-Kwan Cho
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
- KAIST Institute for the BioCentury, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
- Graduate School of Engineering Biology, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
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Ponsetto P, Sasal EM, Mazzoli R, Valetti F, Gilardi G. The potential of native and engineered Clostridia for biomass biorefining. Front Bioeng Biotechnol 2024; 12:1423935. [PMID: 39219620 PMCID: PMC11365079 DOI: 10.3389/fbioe.2024.1423935] [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: 04/26/2024] [Accepted: 08/06/2024] [Indexed: 09/04/2024] Open
Abstract
Since their first industrial application in the acetone-butanol-ethanol (ABE) fermentation in the early 1900s, Clostridia have found large application in biomass biorefining. Overall, their fermentation products include organic acids (e.g., acetate, butyrate, lactate), short chain alcohols (e.g., ethanol, n-butanol, isobutanol), diols (e.g., 1,2-propanediol, 1,3-propanediol) and H2 which have several applications such as fuels, building block chemicals, solvents, food and cosmetic additives. Advantageously, several clostridial strains are able to use cheap feedstocks such as lignocellulosic biomass, food waste, glycerol or C1-gases (CO2, CO) which confer them additional potential as key players for the development of processes less dependent from fossil fuels and with reduced greenhouse gas emissions. The present review aims to provide a survey of research progress aimed at developing Clostridium-mediated biomass fermentation processes, especially as regards strain improvement by metabolic engineering.
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Affiliation(s)
| | | | - Roberto Mazzoli
- Structural and Functional Biochemistry, Laboratory of Proteomics and Metabolic Engineering of Prokaryotes, Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
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Mook A, Herzog J, Walther P, Dürre P, Bengelsdorf FR. Lactate-mediated mixotrophic co-cultivation of Clostridium drakei and recombinant Acetobacterium woodii for autotrophic production of volatile fatty acids. Microb Cell Fact 2024; 23:213. [PMID: 39061103 PMCID: PMC11282840 DOI: 10.1186/s12934-024-02481-3] [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: 03/06/2024] [Accepted: 07/08/2024] [Indexed: 07/28/2024] Open
Abstract
BACKGROUND Acetogens, a diverse group of anaerobic autotrophic bacteria, are promising whole-cell biocatalysts that fix CO2 during their growth. However, because of energetic constraints, acetogens exhibit slow growth and the product spectrum is often limited to acetate. Enabling acetogens to form more valuable products such as volatile fatty acids during autotrophic growth is imperative for cementing their place in the future carbon neutral industry. Co-cultivation of strains with different capabilities has the potential to ease the limiting energetic constraints. The lactate-mediated co-culture of an Acetobacterium woodii mutant strain, capable of lactate production, with the Clostridium drakei SL1 type strain can produce butyrate and hexanoate. In this study, the preceding co-culture is characterized by comparison of monocultures and different co-culture approaches. RESULTS C. drakei grew with H2 + CO2 as main carbon and energy source and thrived when further supplemented with D-lactate. Gas phase components and lactate were consumed in a mixotrophic manner with acetate and butyrate as main products and slight accumulation of hexanoate. Formate was periodically produced and eventually consumed by C. drakei. A lactate-mediated co-culture of the A. woodii [PbgaL_ldhD_NFP] strain, engineered for autotrophic lactate production, and C. drakei produced up to 4 ± 1.7 mM hexanoate and 18.5 ± 5.8 mM butyrate, quadrupling and doubling the respective titers compared to a non-lactate-mediated co-culture. Further co-cultivation experiments revealed the possible advantage of sequential co-culture over concurrent approaches, where both strains are inoculated simultaneously. Scanning electron microscopy of the strains revealed cell-to-cell contact between the co-culture partners. Finally, a combined pathway of A. woodii [PbgaL_ldhD_NFP] and C. drakei for chain-elongation with positive ATP yield is proposed. CONCLUSION Lactate was proven to be a well-suited intermediate to combine the high gas uptake capabilities of A. woodii with the chain-elongation potential of C. drakei. The cell-to-cell contact observed here remains to be further characterized in its nature but hints towards diffusive processes being involved in the co-culture. Furthermore, the metabolic pathways involved are still speculatory for C. drakei and do not fully explain the consumption of formate while H2 + CO2 is available. This study exemplifies the potential of combining metabolically engineered and native bacterial strains in a synthetic co-culture.
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Affiliation(s)
- Alexander Mook
- Institute of Molecular Biology and Biotechnology of Prokaryotes, University of Ulm, Ulm, Germany
| | - Jan Herzog
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany
| | - Paul Walther
- Central Facility for Electron Microscopy, Ulm University, Ulm, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Frank R Bengelsdorf
- Institute of Molecular Biology and Biotechnology of Prokaryotes, University of Ulm, Ulm, Germany.
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Flaiz M, Poehlein A, Wilhelm W, Mook A, Daniel R, Dürre P, Bengelsdorf FR. Refining and illuminating acetogenic Eubacterium strains for reclassification and metabolic engineering. Microb Cell Fact 2024; 23:24. [PMID: 38233843 PMCID: PMC10795377 DOI: 10.1186/s12934-024-02301-8] [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: 10/27/2023] [Accepted: 01/09/2024] [Indexed: 01/19/2024] Open
Abstract
BACKGROUND The genus Eubacterium is quite diverse and includes several acetogenic strains capable of fermenting C1-substrates into valuable products. Especially, Eubacterium limosum and closely related strains attract attention not only for their capability to ferment C1 gases and liquids, but also due to their ability to produce butyrate. Apart from its well-elucidated metabolism, E. limosum is also genetically accessible, which makes it an interesting candidate to be an industrial biocatalyst. RESULTS In this study, we examined genomic, phylogenetic, and physiologic features of E. limosum and the closest related species E. callanderi as well as E. maltosivorans. We sequenced the genomes of the six Eubacterium strains 'FD' (DSM 3662T), 'Marburg' (DSM 3468), '2A' (DSM 2593), '11A' (DSM 2594), 'G14' (DSM 107592), and '32' (DSM 20517) and subsequently compared these with previously available genomes of the E. limosum type strain (DSM 20543T) as well as the strains 'B2', 'KIST612', 'YI' (DSM 105863T), and 'SA11'. This comparison revealed a close relationship between all eleven Eubacterium strains, forming three distinct clades: E. limosum, E. callanderi, and E. maltosivorans. Moreover, we identified the gene clusters responsible for methanol utilization as well as genes mediating chain elongation in all analyzed strains. Subsequent growth experiments revealed that strains of all three clades can convert methanol and produce acetate, butyrate, and hexanoate via reverse β-oxidation. Additionally, we used a harmonized electroporation protocol and successfully transformed eight of these Eubacterium strains to enable recombinant plasmid-based expression of the gene encoding the fluorescence-activating and absorption shifting tag (FAST). Engineered Eubacterium strains were verified regarding their FAST-mediated fluorescence at a single-cell level using a flow cytometry approach. Eventually, strains 'FD' (DSM 3662T), '2A' (DSM 2593), '11A' (DSM 2594), and '32' (DSM 20517) were genetically engineered for the first time. CONCLUSION Strains of E. limosum, E. callanderi, and E. maltosivorans are outstanding candidates as biocatalysts for anaerobic C1-substrate conversion into valuable biocommodities. A large variety of strains is genetically accessible using a harmonized electroporation protocol, and FAST can serve as a reliable fluorescent reporter protein to characterize genetically engineered cells. In total eleven strains have been assigned to distinct clades, providing a clear and updated classification. Thus, the description of respective Eubacterium species has been emended, improved, aligned, and is requested to be implemented in respective databases.
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Affiliation(s)
- Maximilian Flaiz
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands.
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany.
| | - Anja Poehlein
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Georg-August University, Göttingen, Germany
| | - Wiebke Wilhelm
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Alexander Mook
- Institute of Molecular Biology and Biotechnology of Prokaryotes, University of Ulm, Ulm, Germany
| | - Rolf Daniel
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Georg-August University, Göttingen, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Frank R Bengelsdorf
- Institute of Molecular Biology and Biotechnology of Prokaryotes, University of Ulm, Ulm, Germany.
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Herzog J, Mook A, Utesch T, Bengelsdorf FR, Zeng AP. Lactate based caproate production with Clostridium drakei and process control of Acetobacterium woodii via lactate dependent in situ electrolysis. Front Bioeng Biotechnol 2023; 11:1212044. [PMID: 37425355 PMCID: PMC10327822 DOI: 10.3389/fbioe.2023.1212044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 06/15/2023] [Indexed: 07/11/2023] Open
Abstract
Syngas fermentation processes with acetogens represent a promising process for the reduction of CO2 emissions alongside bulk chemical production. However, to fully realize this potential the thermodynamic limits of acetogens need to be considered when designing a fermentation process. An adjustable supply of H2 as electron donor plays a key role in autotrophic product formation. In this study an anaerobic laboratory scale continuously stirred tank reactor was equipped with an All-in-One electrode allowing for in-situ H2 generation via electrolysis. Furthermore, this system was coupled to online lactate measurements to control the co-culture of a recombinant lactate-producing Acetobacterium woodii strain and a lactate-consuming Clostridium drakei strain to produce caproate. When C. drakei was grown in batch cultivations with lactate as substrate, 1.6 g·L-1 caproate were produced. Furthermore, lactate production of the A. woodii mutant strain could manually be stopped and reinitiated by controlling the electrolysis. Applying this automated process control, lactate production of the A. woodii mutant strain could be halted to achieve a steady lactate concentration. In a co-culture experiment with the A. woodii mutant strain and the C. drakei strain, the automated process control was able to dynamically react to changing lactate concentrations and adjust H2 formation respectively. This study confirms the potential of C. drakei as medium chain fatty acid producer in a lactate-mediated, autotrophic co-cultivation with an engineered A. woodii strain. Moreover, the monitoring and control strategy presented in this study reinforces the case for autotrophically produced lactate as a transfer metabolite in defined co-cultivations for value-added chemical production.
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Affiliation(s)
- Jan Herzog
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany
| | - Alexander Mook
- Institute of Molecular Biology and Biotechnology of Prokaryotes, Ulm University, Ulm, Germany
| | - Tyll Utesch
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany
| | - Frank R. Bengelsdorf
- Institute of Molecular Biology and Biotechnology of Prokaryotes, Ulm University, Ulm, Germany
| | - An-Ping Zeng
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany
- Synthetic Biology and Bioengineering Lab, School of Science, Westlake University, Hangzhou, China
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Moreira JPC, Heap JT, Alves JI, Domingues L. Developing a genetic engineering method for Acetobacterium wieringae to expand one-carbon valorization pathways. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:24. [PMID: 36788587 PMCID: PMC9930230 DOI: 10.1186/s13068-023-02259-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 01/05/2023] [Indexed: 02/16/2023]
Abstract
BACKGROUND Developing new bioprocesses to produce chemicals and fuels with reduced production costs will greatly facilitate the replacement of fossil-based raw materials. In most fermentation bioprocesses, the feedstock usually represents the highest cost, which becomes the target for cost reduction. Additionally, the biorefinery concept advocates revenue growth from the production of several compounds using the same feedstock. Taken together, the production of bio commodities from low-cost gas streams containing CO, CO2, and H2, obtained from the gasification of any carbon-containing waste streams or off-gases from heavy industry (steel mills, processing plants, or refineries), embodies an opportunity for affordable and renewable chemical production. To achieve this, by studying non-model autotrophic acetogens, current limitations concerning low growth rates, toxicity by gas streams, and low productivity may be overcome. The Acetobacterium wieringae strain JM is a novel autotrophic acetogen that is capable of producing acetate and ethanol. It exhibits faster growth rates on various gaseous compounds, including carbon monoxide, compared to other Acetobacterium species, making it potentially useful for industrial applications. The species A. wieringae has not been genetically modified, therefore developing a genetic engineering method is important for expanding its product portfolio from gas fermentation and overall improving the characteristics of this acetogen for industrial demands. RESULTS This work reports the development and optimization of an electrotransformation protocol for A. wieringae strain JM, which can also be used in A. wieringae DSM 1911, and A. woodii DSM 1030. We also show the functionality of the thiamphenicol resistance marker, catP, and the functionality of the origins of replication pBP1, pCB102, pCD6, and pIM13 in all tested Acetobacterium strains, with transformation efficiencies of up to 2.0 × 103 CFU/μgDNA. Key factors affecting electrotransformation efficiency include OD600 of cell harvesting, pH of resuspension buffer, the field strength of the electric pulse, and plasmid amount. Using this method, the acetone production operon from Clostridium acetobutylicum was efficiently introduced in all tested Acetobacterium spp., leading to non-native biochemical acetone production via plasmid-based expression. CONCLUSIONS A. wieringae can be electrotransformed at high efficiency using different plasmids with different replication origins. The electrotransformation procedure and tools reported here unlock the genetic and metabolic manipulation of the biotechnologically relevant A. wieringae strains. For the first time, non-native acetone production is shown in A. wieringae.
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Affiliation(s)
- João P. C. Moreira
- grid.10328.380000 0001 2159 175XCEB - Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal ,LABBELS - Associate Laboratory, Braga/Guimarães, Portugal
| | - John T. Heap
- grid.4563.40000 0004 1936 8868School of Life Sciences, University of Nottingham, Biodiscovery Institute, University Park, Nottingham, NG7 2RD UK
| | - Joana I. Alves
- grid.10328.380000 0001 2159 175XCEB - Centre of Biological Engineering, University of Minho, 4710-057 Braga, Portugal ,LABBELS - Associate Laboratory, Braga/Guimarães, Portugal
| | - Lucília Domingues
- CEB - Centre of Biological Engineering, University of Minho, 4710-057, Braga, Portugal. .,LABBELS - Associate Laboratory, Braga/Guimarães, Portugal.
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Herzog J, Mook A, Guhl L, Bäumler M, Beck MH, Weuster‐Botz D, Bengelsdorf FR, Zeng A. Novel synthetic co-culture of Acetobacterium woodii and Clostridium drakei using CO 2 and in situ generated H 2 for the production of caproic acid via lactic acid. Eng Life Sci 2023; 23:e2100169. [PMID: 36619880 PMCID: PMC9815077 DOI: 10.1002/elsc.202100169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 04/07/2022] [Accepted: 05/06/2022] [Indexed: 01/11/2023] Open
Abstract
Acetobacterium woodii is known to produce mainly acetate from CO2 and H2, but the production of higher value chemicals is desired for the bioeconomy. Using chain-elongating bacteria, synthetic co-cultures have the potential to produce longer-chained products such as caproic acid. In this study, we present first results for a successful autotrophic co-cultivation of A. woodii mutants and a Clostridium drakei wild-type strain in a stirred-tank bioreactor for the production of caproic acid from CO2 and H2 via the intermediate lactic acid. For autotrophic lactate production, a recombinant A. woodii strain with a deleted Lct-dehydrogenase complex, which is encoded by the lctBCD genes, and an inserted D-lactate dehydrogenase (LdhD) originating from Leuconostoc mesenteroides, was used. Hydrogen for the process was supplied using an All-in-One electrode for in situ water electrolysis. Lactate concentrations as high as 0.5 g L-1 were achieved with the AiO-electrode, whereas 8.1 g L-1 lactate were produced with direct H2 sparging in a stirred-tank bioreactor. Hydrogen limitation was identified in the AiO process. However, with cathode surface area enlargement or numbering-up of the electrode and on-demand hydrogen generation, this process has great potential for a true carbon-negative production of value chemicals from CO2.
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Affiliation(s)
- Jan Herzog
- Institute of Bioprocess and Biosystems EngineeringHamburg University of TechnologyHamburgGermany
| | - Alexander Mook
- Institute of Microbiology and BiotechnologyUlm UniversityUlmGermany
| | - Lotta Guhl
- Institute of Bioprocess and Biosystems EngineeringHamburg University of TechnologyHamburgGermany
| | - Miriam Bäumler
- Department of Energy and Process EngineeringChair of Biochemical EngineeringTechnical University of MunichTUM School of Engineering and DesignGarchingGermany
| | - Matthias H. Beck
- Institute of Microbiology and BiotechnologyUlm UniversityUlmGermany
| | - Dirk Weuster‐Botz
- Department of Energy and Process EngineeringChair of Biochemical EngineeringTechnical University of MunichTUM School of Engineering and DesignGarchingGermany
| | | | - An‐Ping Zeng
- Institute of Bioprocess and Biosystems EngineeringHamburg University of TechnologyHamburgGermany
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Baur T, Wentzel A, Dürre P. Production of propionate using metabolically engineered strains of Clostridium saccharoperbutylacetonicum. Appl Microbiol Biotechnol 2022; 106:7547-7562. [PMID: 36282302 PMCID: PMC9666320 DOI: 10.1007/s00253-022-12210-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 12/04/2022]
Abstract
Abstract The carboxylic acid propionate is a valuable platform chemical with applications in various fields. The biological production of this acid has become of great interest as it can be considered a sustainable alternative to petrochemical synthesis. In this work, Clostridium saccharoperbutylacetonicum was metabolically engineered to produce propionate via the acrylate pathway. In total, the established synthetic pathway comprised eight genes encoding the enzymes catalyzing the conversion of pyruvate to propionate. These included the propionate CoA-transferase, the lactoyl-CoA dehydratase, and the acryloyl-CoA reductase from Anaerotignum neopropionicum as well as a D-lactate dehydrogenase from Leuconostoc mesenteroides subsp. mesenteroides. Due to difficulties in assembling all genes on one plasmid under the control of standard promoters, the PtcdB-tcdR promoter system from Clostridium difficile was integrated into a two-plasmid system carrying the acrylate pathway genes. Several promoters were analyzed for their activity in C. saccharoperbutylacetonicum using the fluorescence-activating and absorption-shifting tag (FAST) as a fluorescent reporter to identify suitable candidates to drive tcdR expression. After selecting the lactose-inducible PbgaL promoter, engineered C. saccharoperbutylacetonicum strains produced 0.7 mM propionate upon induction of gene expression. The low productivity was suspected to be a consequence of a metabolic imbalance leading to acryloyl-CoA accumulation in the cells. To even out the proposed imbalance, the propionate-synthesis operons were rearranged, thereby increasing the propionate concentration by almost four-fold. This study is the first one to report recombinant propionate production using a clostridial host strain that has opened a new path towards bio-based propionate to be improved further in subsequent work. Key points • Determination of promoter activities in C. saccharoperbutylacetonicum using FAST. • Implementation of propionate production in C. saccharoperbutylacetonicum. • Elevation of propionate production by 375% to a concentration of 3 mM. Supplementary Information The online version contains supplementary material available at 10.1007/s00253-022-12210-8.
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Baur ST, Poehlein A, Renz NJ, Hollitzer SK, Montoya Solano JD, Schiel-Bengelsdorf B, Daniel R, Dürre P. Modulation of sol mRNA expression by the long non-coding RNA Assolrna in Clostridium saccharoperbutylacetonicum affects solvent formation. Front Genet 2022; 13:966643. [PMID: 36035128 PMCID: PMC9402939 DOI: 10.3389/fgene.2022.966643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 07/11/2022] [Indexed: 12/01/2022] Open
Abstract
Solvents such as butanol are important platform chemicals and are often produced from petrochemical sources. Production of butanol and other compounds from renewable and sustainable resources can be achieved by solventogenic bacteria, such as the hyper-butanol producer Clostridium saccharoperbutylacetonicum. Its sol operon consists of the genes encoding butyraldehyde dehydrogenase, CoA transferase, and acetoacetate decarboxylase (bld, ctfA, ctfB, adc) and the gene products are involved in butanol and acetone formation. It is important to understand its regulation to further optimize the solvent production. In this study, a new long non-coding antisense transcript complementary to the complete sol operon, now called Assolrna, was identified by transcriptomic analysis and the regulatory mechanism of Assolrna was investigated. For this purpose, the promoter-exchange strain C. saccharoperbutylacetonicum ΔPasr::Pasr** was constructed. Additionally, Assolrna was expressed plasmid-based under control of the native Pasr promoter and the lactose-inducible PbgaL promoter in both the wild type and the promoter-exchange strain. Solvent formation was strongly decreased for all strains based on C. saccharoperbutylacetonicum ΔPasr::Pasr** and growth could not be restored by plasmid-based complementation of the exchanged promoter. Interestingly, very little sol mRNA expression was detected in the strain C. saccharoperbutylacetonicum ΔPasr::Pasr** lacking Assolrna expression. Butanol titers were further increased for the overexpression strain C. saccharoperbutylacetonicum [pMTL83151_asr_PbgaL] compared to the wild type. These results suggest that Assolrna has a positive effect on sol operon expression. Therefore, a possible stabilization mechanism of the sol mRNA by Assolrna under physiological concentrations is proposed.
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Affiliation(s)
- Saskia Tabea Baur
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
- *Correspondence: Saskia Tabea Baur,
| | - Anja Poehlein
- Department of Genomic and Applied Microbiology and Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Niklas Jan Renz
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | | | | | | | - Rolf Daniel
- Department of Genomic and Applied Microbiology and Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
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Vees CA, Herwig C, Pflügl S. Mixotrophic co-utilization of glucose and carbon monoxide boosts ethanol and butanol productivity of continuous Clostridium carboxidivorans cultures. BIORESOURCE TECHNOLOGY 2022; 353:127138. [PMID: 35405210 DOI: 10.1016/j.biortech.2022.127138] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/05/2022] [Accepted: 04/06/2022] [Indexed: 06/14/2023]
Abstract
In this study, continuous cultivations of C.carboxidivorans to study heterotrophic and mixotrophic conversion of glucose and H2, CO2, and CO were established. Glucose fermentations at pH 6 showed a high ratio of alcohol-to-acid production of 2.79 mol mol-1. While H2 or CO2 were not utilized together with glucose, CO feeding drastically increased the combined alcohol titer to 9.1 g l-1. Specifically, CO enhanced acetate (1.9-fold) and ethanol (1.7-fold) production and triggered chain elongation to butanol (1.5-fold) production but did not change the alcohol:acid ratio. Flux balance analysis showed that CO served both as a carbon and energy source, and CO mixotrophy displayed a carbon and energy efficiency of 45 and 77%, respectively. This study expands the knowledge on physiology and metabolism of C.carboxidivorans and can serve as the starting point for rational engineering and process intensification to establish efficient production of alcohols and acids from carbon waste.
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Affiliation(s)
- Charlotte Anne Vees
- Technische Universität Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Gumpendorfer Straße 1a, 1060 Vienna, Austria.
| | - Christoph Herwig
- Technische Universität Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Gumpendorfer Straße 1a, 1060 Vienna, Austria; Competence Center CHASE GmbH, Altenbergerstraße 69, 4040 Linz, Austria.
| | - Stefan Pflügl
- Technische Universität Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Area Biochemical Engineering, Gumpendorfer Straße 1a, 1060 Vienna, Austria.
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Lauer I, Philipps G, Jennewein S. Metabolic engineering of Clostridium ljungdahlii for the production of hexanol and butanol from CO 2 and H 2. Microb Cell Fact 2022; 21:85. [PMID: 35568911 PMCID: PMC9107641 DOI: 10.1186/s12934-022-01802-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/11/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The replacement of fossil fuels and petrochemicals with sustainable alternatives is necessary to mitigate the effects of climate change and also to counteract diminishing fossil resources. Acetogenic microorganisms such as Clostridium spp. are promising sources of fuels and basic chemical precursors because they efficiently utilize CO and CO2 as carbon source. However the conversion into high titers of butanol and hexanol is challenging. RESULTS Using a metabolic engineering approach we transferred a 17.9-kb gene cluster via conjugation, containing 13 genes from C. kluyveri and C. acetobutylicum for butanol and hexanol biosynthesis, into C. ljungdahlii. Plasmid-based expression resulted in 1075 mg L-1 butanol and 133 mg L-1 hexanol from fructose in complex medium, and 174 mg L-1 butanol and 15 mg L-1 hexanol from gaseous substrate (20% CO2 and 80% H2) in minimal medium. Product formation was increased by the genomic integration of the heterologous gene cluster. We confirmed the expression of all 13 enzymes by targeted proteomics and identified potential rate-limiting steps. Then, we removed the first-round selection marker using CRISPR/Cas9 and integrated an additional 7.8 kb gene cluster comprising 6 genes from C. carboxidivorans. This led to a significant increase in the hexanol titer (251 mg L-1) at the expense of butanol (158 mg L-1), when grown on CO2 and H2 in serum bottles. Fermentation of this strain at 2-L scale produced 109 mg L-1 butanol and 393 mg L-1 hexanol. CONCLUSIONS We thus confirmed the function of the butanol/hexanol biosynthesis genes and achieved hexanol biosynthesis in the syngas-fermenting species C. ljungdahlii for the first time, reaching the levels produced naturally by C. carboxidivorans. The genomic integration strain produced hexanol without selection and is therefore suitable for continuous fermentation processes.
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Affiliation(s)
- Ira Lauer
- Department for Industrial Biotechnology, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Forckenbeckstr. 6, 52074, Aachen, Germany
| | - Gabriele Philipps
- Department for Industrial Biotechnology, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Forckenbeckstr. 6, 52074, Aachen, Germany
| | - Stefan Jennewein
- Department for Industrial Biotechnology, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Forckenbeckstr. 6, 52074, Aachen, Germany.
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Increased Butyrate Production in Clostridium saccharoperbutylacetonicum from Lignocellulose-Derived Sugars. Appl Environ Microbiol 2022; 88:e0241921. [PMID: 35311509 DOI: 10.1128/aem.02419-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Butyrate is produced by chemical synthesis based on crude oil, produced by microbial fermentation, or extracted from animal fats (M. Dwidar, J.-Y. Park, R. J. Mitchell, and B.-I. Sang, The Scientific World Journal, 2012:471417, 2012, https://doi.org/10.1100/2012/471417). Butyrate production by anaerobic bacteria is highly favorable since waste or sustainable resources can be used as the substrates. For this purpose, the native hyper-butanol producer Clostridium saccharoperbutylacetonicum N1-4(HMT) was used as a chassis strain due to its broad substrate spectrum. BLASTp analysis of the predicted proteome of C. saccharoperbutylacetonicum N1-4(HMT) resulted in the identification of gene products potentially involved in acetone-butanol-ethanol (ABE) fermentation. Their participation in ABE fermentation was either confirmed or disproven by the parallel production of acids or solvents and the respective transcript levels obtained by transcriptome analysis of this strain. The genes encoding phosphotransacetylase (pta) and butyraldehyde dehydrogenase (bld) were deleted to reduce acetate and alcohol formation. The genes located in the butyryl-CoA synthesis (bcs) operon encoding crotonase, butyryl-CoA dehydrogenase with electron-transferring protein subunits α and β, and 3-hydroxybutyryl-CoA dehydrogenase were overexpressed to channel the flux further towards butyrate formation. Thereby, the native hyper-butanol producer C. saccharoperbutylacetonicum N1-4(HMT) was converted into the hyper-butyrate producer C. saccharoperbutylacetonicum ΔbldΔpta [pMTL83151_BCS_PbgaL]. The transcription pattern following deletion and overexpression was characterized by a second transcriptomic study, revealing partial compensation for the deletion. Furthermore, this strain was characterized in pH-controlled fermentations with either glucose or Excello, a substrate yielded from spruce biomass. Butyrate was the main product, with maximum butyrate concentrations of 11.7 g·L-1 and 14.3 g·L-1, respectively. Minimal amounts of by-products were detected. IMPORTANCE Platform chemicals such as butyrate are usually produced chemically from crude oil, resulting in the carry-over of harmful compounds. The selective production of butyrate using sustainable resources or waste without harmful by-products can be achieved by bacteria such as clostridia. The hyper-butanol producer Clostridium saccharoperbutylacetonicum N1-4(HMT) was converted into a hyper-butyrate producer. Butyrate production with very small amounts of by-products was established with glucose and the sustainable lignocellulosic sugar substrate Excello extracted from spruce biomass by the biorefinery Borregaard (Sarpsborg, Norway).
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Flaiz M, Baur T, Gaibler J, Kröly C, Dürre P. Establishment of Green- and Red-Fluorescent Reporter Proteins Based on the Fluorescence-Activating and Absorption-Shifting Tag for Use in Acetogenic and Solventogenic Anaerobes. ACS Synth Biol 2022; 11:953-967. [PMID: 35081709 DOI: 10.1021/acssynbio.1c00554] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Anaerobic bacteria are promising biocatalysts to produce industrially relevant products from nonfood feedstocks. Several anaerobes are genetically accessible, and various molecular tools for metabolic engineering are available. Still, the use of bright fluorescent reporters, which are commonly used in molecular biological approaches is limited under anaerobic conditions. Therefore, the establishment of different anaerobic fluorescent reporter proteins is of great interest. Here, we present the establishment of the green- and red-fluorescent reporter proteins greenFAST and redFAST for use in different solventogenic and acetogenic bacteria. Green fluorescence of greenFAST was bright in Clostridium saccharoperbutylacetonicum, Clostridium acetobutylicum, Acetobacterium woodii, and Eubacterium limosum, while only C. saccharoperbutylacetonicum showed bright red fluorescence when producing redFAST. We used both reporter proteins in C. saccharoperbutylacetonicum for multicolor approaches. These include the investigation of the co-culture dynamics of metabolically engineered strains. Moreover, we established a tightly regulated inducible two-plasmid system and used greenFAST and redFAST to track the coexistence and interaction of both plasmids under anaerobic conditions in C. saccharoperbutylacetonicum. The establishment of greenFAST and redFAST as fluorescent reporters opens the door for further multicolor approaches to investigate cell dynamics, gene expression, or protein localization under anaerobic conditions.
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Affiliation(s)
- Maximilian Flaiz
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Tina Baur
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Jana Gaibler
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Christian Kröly
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Peter Dürre
- Institute of Microbiology and Biotechnology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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