A synthetic two-member cellulose-to-ethanol coculture pairing the cellulolytic mesophile Clostridium phytofermentans ISDg, currently represented in NCBI Taxonomy as Lachnoclostridium phytofermentans ISDg, with the engineered cellodextrin-fermenting yeast Saccharomyces cerevisiae cdt-1. The consortium is maintained by controlled oxygen delivery: the yeast removes inhibitory oxygen and receives soluble sugars released during C. phytofermentans cellulose hydrolysis. With added endoglucanase, the coculture produced approximately 22 g/L ethanol from 100 g/L alpha-cellulose. This system is relevant to DOE lignocellulosic biofuel and consolidated bioprocessing goals.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Clostridium phytofermentans ISDg — ontology label: Lachnoclostridium phytofermentans ISDg | NCBITaxon:357809 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SECONDARY_FERMENTER
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ABUNDANT |
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| Saccharomyces cerevisiae cdt-1 — ontology label: Saccharomyces cerevisiae | NCBITaxon:4932 · TaxonMech · TraitMech |
CROSS_FEEDER
SECONDARY_FERMENTER
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ABUNDANT |
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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 Feeds Yeast Fermentation
CROSS_FEEDINGC. phytofermentans hydrolysis supplies soluble sugars, including cellodextrins and glucose, that support S. cerevisiae cdt-1. Cellulose is the upstream feedstock. The approximately 22 g/L ethanol result used added endoglucanase; unsupplemented coculture did not show the same productivity improvement. Under the low-oxygen ethanol-production regime, ethanol is an output rather than the proposed sugar-transfer currency.
Source Taxon: Clostridium phytofermentans ISDg
Target Taxon: Saccharomyces cerevisiae cdt-1
Metabolites: cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech), glucose (CHEBI:17234 · MediaIngredientMech · CMMMech), ethanol (CHEBI:16236 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
- fermentation (GO:0006113 · PathwayMech)
Bacterial cellulose hydrolysis provides soluble carbon that can sustain yeast in the oxygen-controlled culture. PARTIAL - the long-term viable-count comparison supports this cooperation but does not directly partition carbon transfer or isolate every stabilizing mechanism.
Evidence
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PMID:23628342 - SUPPORT (IN_VITRO)"soluble sugars released by C. phytofermentans hydrolysis"
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PMID:23628342 - SUPPORT (IN_VITRO)"produced approximately 22 g/L ethanol"
Oxygen Protection of Anaerobic Cellulolytic Partner
MUTUALISMThe oxygen-removal arm of a condition-dependent mutualism protects oxygen-sensitive C. phytofermentans, while bacterial sugar supply benefits the yeast. Semi-aerobic mono-/coculture comparisons support respiratory protection, and controlled low oxygen delivery supports yeast persistence. This is not a claim that either organism universally requires its partner under other culture conditions.
Source Taxon: Saccharomyces cerevisiae cdt-1
Target Taxon: Clostridium phytofermentans ISDg
Metabolites: oxygen (CHEBI:15379 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
PARTIAL - yeast respiratory protection together with oxygen-supported yeast growth and bacterial sugar supply can stabilize the pairing. Oxygen-positive versus oxygen-negative viable-count controls support the conditional cooperation, without selectively measuring every mediator.
Evidence
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PMID:23628342 - SUPPORT (IN_VITRO)"“protect” C. phytofermentans from introduced oxygen"
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PMID:23628342 - SUPPORT (IN_VITRO)"maintained by controlled oxygen transport"
Oxygen-Dependent Long-Term Population Maintenance
With controlled oxygen delivery, both partners remained culturable at the reported 30-, 40- and 50-day samples; without oxygen the yeast fell below detection before day 30. This long-term arm used 25 mL medium and 150 g/L alpha-cellulose. Population maintenance is a community outcome, distinct from the enzyme-assisted ethanol experiment and from an unconditional mutualism claim.
Participating Taxa: Clostridium phytofermentans ISDg, Saccharomyces cerevisiae cdt-1
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:23628342 - SUPPORT (IN_VITRO)"maintenance of populations of 105 to 106 CFU/mL for 50 days"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How do oxygen delivery and hydrolytic capacity separately control persistence and ethanol productivity?
The oxygen controls support conditional cooperation and viable population maintenance, while additional endoglucanase improves conversion. These are different experimental arms. Mediator-specific or partner-resolved measurements would separate respiratory protection, sugar supply and enzyme effects without inferring universal obligacy or unsupplemented productivity gains.
Attaches to: ecological_interactions#Cellulose Hydrolysis Feeds Yeast Fermentation, ecological_interactions#Oxygen Protection of Anaerobic Cellulolytic Partner, ecological_interactions#Oxygen-Dependent Long-Term Population Maintenance
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Exact-system primary publication - cellulose-to-ethanol symbiotic coculture
Primary PubMed record for the C. phytofermentans and S. cerevisiae cdt-1 cellulose-to-ethanol coculture. |
OTHER | PMID:23628342 |
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Full-text open-access article
Full-text article with reactor design, culture conditions, and comparative mono- and coculture data. |
OTHER | PMCID:PMC3653780 |
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DOI landing page
DOI for the Biotechnology for Biofuels publication. |
OTHER | doi:10.1186/1754-6834-6-59 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Controlled oxygen transfer | approximately 8 micromol/L hour diffusive oxygen delivery | N/A |
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| Semi-aerobic cellulose degradation | filter paper and alpha-cellulose under semi-aerobic coculture conditions | N/A |
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| Added endoglucanase | added endoglucanase during high-cellulose fermentation | N/A |
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| Ethanol titer | approximately 22 g/L ethanol from 100 g/L alpha-cellulose | N/A |
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Growth Media
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