Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids
Abstract Hexanoate is a valuable chemical that can be produced by microorganisms that convert short-chain- to medium-chain carboxylic acids through a process called chain elongation. These microorganisms usually produce mixtures of butyrate and hexanoate from ethanol and acetate, but direct conversi...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2023-10-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-023-43682-x |
| _version_ | 1797576678706249728 |
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| author | Maximilienne Toetie Allaart Bartholomeus B. Fox Ingo H. M. S. Nettersheim Martin Pabst Diana Z. Sousa Robbert Kleerebezem |
| author_facet | Maximilienne Toetie Allaart Bartholomeus B. Fox Ingo H. M. S. Nettersheim Martin Pabst Diana Z. Sousa Robbert Kleerebezem |
| author_sort | Maximilienne Toetie Allaart |
| collection | DOAJ |
| description | Abstract Hexanoate is a valuable chemical that can be produced by microorganisms that convert short-chain- to medium-chain carboxylic acids through a process called chain elongation. These microorganisms usually produce mixtures of butyrate and hexanoate from ethanol and acetate, but direct conversion of ethanol to hexanoate is theoretically possible. Steering microbial communities to ethanol-only elongation to hexanoate circumvents the need for acetate addition and simplifies product separation. The biological feasibility of ethanol elongation to hexanoate was validated in batch bioreactor experiments with a Clostridium kluyveri-dominated enrichment culture incubated with ethanol, acetate and butyrate in different ratios. Frequent liquid sampling combined with high-resolution off-gas measurements allowed to monitor metabolic behavior. In experiments with an initial ethanol-to-acetate ratio of 6:1, acetate depletion occurred after ± 35 h of fermentation, which triggered a metabolic shift to direct conversion of ethanol to hexanoate despite the availability of butyrate (± 40 mCmol L−1). When only ethanol and no external electron acceptor was supplied, stable ethanol to hexanoate conversion could be maintained until 60–90 mCmol L−1 of hexanoate was produced. After this, transient production of either acetate and butyrate or butyrate and hexanoate was observed, requiring a putative reversal of the Rnf complex. This was not observed before acetate depletion or in presence of low concentrations (40–60 mCmol L−1) of butyrate, suggesting a stabilizing or regulatory role of butyrate or butyrate-related catabolic intermediates. This study sheds light on previously unknown versatility of chain elongating microbes and provides new avenues for optimizing (waste) bioconversion for hexanoate production. |
| first_indexed | 2024-03-10T21:57:12Z |
| format | Article |
| id | doaj.art-28612c38076f486f9cf8c05d1ff4b821 |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-03-10T21:57:12Z |
| publishDate | 2023-10-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-28612c38076f486f9cf8c05d1ff4b8212023-11-19T13:04:51ZengNature PortfolioScientific Reports2045-23222023-10-0113111010.1038/s41598-023-43682-xPhysiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acidsMaximilienne Toetie Allaart0Bartholomeus B. Fox1Ingo H. M. S. Nettersheim2Martin Pabst3Diana Z. Sousa4Robbert Kleerebezem5Department of Biotechnology, Delft University of TechnologyDepartment of Biotechnology, Delft University of TechnologyDepartment of Biotechnology, Delft University of TechnologyDepartment of Biotechnology, Delft University of TechnologyLaboratory of Microbiology, Wageningen University & ResearchDepartment of Biotechnology, Delft University of TechnologyAbstract Hexanoate is a valuable chemical that can be produced by microorganisms that convert short-chain- to medium-chain carboxylic acids through a process called chain elongation. These microorganisms usually produce mixtures of butyrate and hexanoate from ethanol and acetate, but direct conversion of ethanol to hexanoate is theoretically possible. Steering microbial communities to ethanol-only elongation to hexanoate circumvents the need for acetate addition and simplifies product separation. The biological feasibility of ethanol elongation to hexanoate was validated in batch bioreactor experiments with a Clostridium kluyveri-dominated enrichment culture incubated with ethanol, acetate and butyrate in different ratios. Frequent liquid sampling combined with high-resolution off-gas measurements allowed to monitor metabolic behavior. In experiments with an initial ethanol-to-acetate ratio of 6:1, acetate depletion occurred after ± 35 h of fermentation, which triggered a metabolic shift to direct conversion of ethanol to hexanoate despite the availability of butyrate (± 40 mCmol L−1). When only ethanol and no external electron acceptor was supplied, stable ethanol to hexanoate conversion could be maintained until 60–90 mCmol L−1 of hexanoate was produced. After this, transient production of either acetate and butyrate or butyrate and hexanoate was observed, requiring a putative reversal of the Rnf complex. This was not observed before acetate depletion or in presence of low concentrations (40–60 mCmol L−1) of butyrate, suggesting a stabilizing or regulatory role of butyrate or butyrate-related catabolic intermediates. This study sheds light on previously unknown versatility of chain elongating microbes and provides new avenues for optimizing (waste) bioconversion for hexanoate production.https://doi.org/10.1038/s41598-023-43682-x |
| spellingShingle | Maximilienne Toetie Allaart Bartholomeus B. Fox Ingo H. M. S. Nettersheim Martin Pabst Diana Z. Sousa Robbert Kleerebezem Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids Scientific Reports |
| title | Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids |
| title_full | Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids |
| title_fullStr | Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids |
| title_full_unstemmed | Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids |
| title_short | Physiological and stoichiometric characterization of ethanol-based chain elongation in the absence of short-chain carboxylic acids |
| title_sort | physiological and stoichiometric characterization of ethanol based chain elongation in the absence of short chain carboxylic acids |
| url | https://doi.org/10.1038/s41598-023-43682-x |
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