High-cell-density syntrophic bacterial coculture pairing genetically engineered Clostridium acetobutylicum (CACas9 delta-hbd-p95ace02_atoB, lacking 4-C metabolism and overexpressing an acetone-formation pathway) with the acetogen and ketoreductase partner Clostridium ljungdahlii in a 3.6-L perfusion bioreactor. C. acetobutylicum ferments glucose to acetone, CO2, and H2; C. ljungdahlii consumes dissolved H2—relieving the thermodynamic bottleneck of NADH-driven H2 evolution in C. acetobutylicum—and reduces cross-fed acetone to isopropanol at supratheoretical yields in continuous carbon-negative glucose fermentation.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Clostridium acetobutylicum | NCBITaxon:1488 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SECONDARY_FERMENTER
CROSS_FEEDER
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DOMINANT |
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| Clostridium ljungdahlii | NCBITaxon:1538 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
SECONDARY_FERMENTER
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DOMINANT |
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Ecological Interactions
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Syntrophic Hydrogen Scavenging Relieving NADH-Driven Thermodynamic Limitation
SYNTROPHYClostridium ljungdahlii scavenges H2 evolved during glucose fermentation by engineered Clostridium acetobutylicum CACas9 Δhbd-p95ace02_atoB, eliminating detectable H2 accumulation and relieving the thermodynamic bottleneck on NADH-driven H2 evolution and acetone production.
Source Taxon: Clostridium ljungdahlii
Target Taxon: Clostridium acetobutylicum
Metabolites: glucose (CHEBI:17234 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)
Biological Processes:
- glucose metabolic process (GO:0006006 · PathwayMech)
- hydrogen biosynthetic process (GO:1902422 · PathwayMech)
DIRECTLY IMPLIED: Relief of NADH-driven H2 thermodynamic inhibition enables high-yield acetone synthesis by C. acetobutylicum and subsequent cross-feeding of acetone to C. ljungdahlii for reduction to isopropanol.
Evidence
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PMID:41831593 - SUPPORT (IN_VITRO)"To explore the potential of this coculture system to achieve supratheoretical isopropanol yields, we identify NADH-driven hydrogen conversion in CACas9 Δhbd-p95ace02_atoB as the thermodynamically limiting step for acetone production in monocultures and thus isopropanol production in cocultures. We then demonstrate the ability of C. ljungdahlii to mitigate this issue by eliminating detectable hydrogen accumulation in the coculture."
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PMID:41831593 - SUPPORT (IN_VITRO)"CACas9 Δhbd-p95ace02_atoB produces acetone without 4-C metabolites and C. ljungdahlii converts the acetone to isopropanol."
Acetone Cross-Feeding and Reduction to Isopropanol
CROSS_FEEDINGEngineered Clostridium acetobutylicum CACas9 Δhbd-p95ace02_atoB ferments glucose to acetone without 4-carbon byproducts, and Clostridium ljungdahlii reduces the cross-fed acetone to isopropanol.
Source Taxon: Clostridium acetobutylicum
Target Taxon: Clostridium ljungdahlii
Metabolites: glucose (CHEBI:17234 · MediaIngredientMech · CMMMech), acetone (CHEBI:15347 · MediaIngredientMech · CMMMech)
Biological Processes:
- glucose metabolic process (GO:0006006 · PathwayMech)
DIRECTLY IMPLIED: Coupled H2 scavenging and acetone-to-isopropanol cross-feeding at high C. ljungdahlii cell density achieve supratheoretical, carbon-negative isopropanol production in perfusion bioreactors.
Evidence
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PMID:41831593 - SUPPORT (IN_VITRO)"CACas9 Δhbd-p95ace02_atoB produces acetone without 4-C metabolites and C. ljungdahlii converts the acetone to isopropanol."
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PMID:41831593 - SUPPORT (IN_VITRO)"Pseudo-perfusion cocultures showed that high cell densities combined with a high population fraction of C. ljungdahlii enable dramatic increases in isopropanol yields beyond the thermodynamic limitation imposed in CACas9 Δhbd-p95ace02_atoB monocultures."
High-Cell-Density Continuous Carbon-Negative Isopropanol Fermentation
SYNTROPHYIn pseudo-perfusion and 3.6-L perfusion bioreactors with high cell density and high Clostridium ljungdahlii population fraction, the syntrophic coculture achieves supratheoretical, carbon-negative conversion of glucose to isopropanol as the sole alcohol product.
Source Taxon: Clostridium acetobutylicum
Target Taxon: Clostridium ljungdahlii
Metabolites: glucose (CHEBI:17234 · MediaIngredientMech · CMMMech), acetone (CHEBI:15347 · MediaIngredientMech · CMMMech)
Biological Processes:
- glucose metabolic process (GO:0006006 · PathwayMech)
Evidence
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PMID:41831593 - SUPPORT (IN_VITRO)"Finally, we demonstrate a continuous carbon-negative fermentation of glucose to isopropanol as the sole alcohol produced from glucose in a 3.6-L scale perfusion bioreactor."
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Cell Density and C. ljungdahlii Population Fraction in Perfusion Bioreactor | 3.6-L continuous perfusion bioreactor with high C. ljungdahlii population fraction | N/A |
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