A thermophilic, anaerobic, two-member laboratory coculture for consolidated cellulosic bioethanol production. The cellulolytic Clostridium thermocellum LQRI member hydrolyzes and ferments cellulose, while the non-cellulolytic Thermoanaerobacter pseudethanolicus strain X514 partner improves ethanol production from cellulose-derived fermentation intermediates. The system is DOE-relevant because it uses a defined coculture to increase ethanolic fermentation of recalcitrant cellulosic material under batch and cyclic fed-batch bioprocess conditions.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Clostridium thermocellum LQRI — ontology label: Acetivibrio thermocellus DSM 2360 | NCBITaxon:572545 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SECONDARY_FERMENTER
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N/A |
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| Thermoanaerobacter pseudethanolicus strain X514 — ontology label: Thermoanaerobacter sp. X514 | NCBITaxon:399726 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
CROSS_FEEDER
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N/A |
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Ecological Interactions
The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.
Cellulose Hydrolysis Supporting Coculture Fermentation
CROSS_FEEDINGPARTIAL - LQRI hydrolysis is proposed to supply soluble sugars to noncellulolytic, saccharolytic X514. Lower sugar accumulation in coculture supports this model, not directly traced transfer. Cellulose is the feedstock and ethanol the output, not the exchanged compounds; improved ethanol production does not imply universally improved cellulose utilization.
Source Taxon: Clostridium thermocellum LQRI
Target Taxon: Thermoanaerobacter pseudethanolicus strain X514
Metabolites: cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech), ethanol (CHEBI:16236 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
- fermentation (GO:0006113 · PathwayMech)
PARTIAL - access to LQRI-derived soluble sugars can support X514 fermentation and higher community ethanol output. Partner flux and the separate contributions of sugar removal and operating conditions remain unresolved.
Evidence
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PMID:23275517 - PARTIAL (IN_VITRO)"improve bioethanol production from the fermentation of recalcitrant cellulosic materials"
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PMID:23275517 - PARTIAL (IN_VITRO)"tested in the semicontinuous fermentor as a model system"
Enhanced Ethanol Output in X514 Cocultures
The 2011 abstract reports greater ethanol output in C. thermocellum cocultures and stronger enhancement with X514 than 39E. The separate LQRI-X514 fed-batch study shows condition-dependent improvements relative to LQRI monoculture. This is a community product phenotype, not demonstrated ethanol donation from X514 to LQRI.
Participating Taxa: Clostridium thermocellum LQRI, Thermoanaerobacter pseudethanolicus strain X514
Metabolites: ethanol (CHEBI:16236 · MediaIngredientMech · CMMMech)
Biological Processes:
- fermentation (GO:0006113 · PathwayMech)
Evidence
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PMID:21868218 - SUPPORT (IN_VITRO)"improved ethanol production by 194-440%"
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PMID:21868218 - SUPPORT (IN_VITRO)"Strain X514 enhanced ethanolic fermentation much more effectively"
X514 B12 Biosynthesis and Proposed Fermentation Support
PARTIAL - comparative genomes associate X514 performance with B12 biosynthesis capacity; supplementation improved 39E ethanol production. This supports a proposed cofactor-related contribution, not demonstrated vitamin donation to LQRI or commensalism. The separate fed-batch study supplied vitamins and does not establish B12 autonomy.
Source Taxon: Thermoanaerobacter pseudethanolicus strain X514
Metabolites: cobalamin (CHEBI:30411 · MediaIngredientMech · CMMMech)
Biological Processes:
- cobalamin biosynthetic process (GO:0009236 · PathwayMech)
HYPOTHESIZED - B12 biosynthesis may support X514 fermentation and thereby contribute to coculture ethanol output. Comparative genomes and the 39E supplementation response support this proposal, but do not selectively establish the causal contribution in X514.
Evidence
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PMID:21868218 - PARTIAL (IN_VITRO)"complete vitamin B(12) biosynthesis pathway"
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PMID:21868218 - PARTIAL (IN_VITRO)"improved ethanol production in strain 39E by 203%"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN What is the causal contribution of sugar exchange and X514 B12 biosynthesis to community ethanol output?
Partner-resolved flux and selective X514 perturbation would distinguish the proposed mechanisms. The 2011 abstract supports the comparative association and 39E supplementation response, not vitamin transfer. The 2013 fed-batch medium contains added vitamins and its process comparisons are not a test of biosynthetic autonomy.
Attaches to: ecological_interactions#Cellulose Hydrolysis Supporting Coculture Fermentation, ecological_interactions#Enhanced Ethanol Output in X514 Cocultures, ecological_interactions#X514 B12 Biosynthesis and Proposed Fermentation Support
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Mechanisms of enhanced cellulosic bioethanol fermentation by co-cultivation
Primary publication reporting C. thermocellum cocultures with Thermoanaerobacter X514 and 39E, including X514-linked ethanol enhancement and vitamin B12 pathway analysis. |
OTHER | PMID:21868218 |
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Continuous cellulosic bioethanol fermentation by cyclic fed-batch cocultivation
Primary publication reporting the exact C. thermocellum LQRI and Thermoanaerobacter pseudethanolicus X514 coculture in cyclic fed-batch cellulose fermentation. |
OTHER | PMID:23275517 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Initial cellulose concentration | 40 to 80 g liter(-1) cellulose | N/A |
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| pH control | pH 6.5 to 6.8 | N/A |
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Growth Media
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