A heterogeneous 3-member consortium for direct conversion of lignocellulose to short-chain fatty acids (SCFAs), specifically butyric acid. The platform consists of Trichoderma reesei Rut-C30 (aerobic fungus producing cellulases), Lactobacillus pentosus (facultative anaerobic lactic acid bacterium), and Clostridium tyrobutyricum (obligate anaerobic butyrate producer). Sequential inoculation creates an oxygen gradient allowing coexistence of all members. T. reesei degrades cellulose to sugars, LAB converts sugars to lactate and creates anaerobic conditions, and C. tyrobutyricum ferments lactate to butyrate, achieving 196 kg butyric acid per metric ton of beechwood.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Trichoderma reesei Rut-C30 — ontology label: Trichoderma reesei | NCBITaxon:51453 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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DOMINANT |
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| Lactobacillus pentosus — ontology label: Lactiplantibacillus pentosus | NCBITaxon:1589 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
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ABUNDANT |
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| Clostridium tyrobutyricum | NCBITaxon:1519 · TaxonMech · TraitMech |
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 to Soluble Sugars
CROSS_FEEDINGT. reesei hydrolysis supplies soluble carbohydrates to L. pentosus in the membrane reactor. Cellulose supplies hexose products; xylose belongs to the separately supplied pentose or hemicellulose fraction, not cellulose hydrolysis. This food-chain link does not establish reciprocal thermodynamic syntrophy.
Source Taxon: Trichoderma reesei Rut-C30
Target Taxon: Lactobacillus pentosus
Metabolites: cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech), glucose (CHEBI:17234 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
Fungal hydrolysis supplies fermentable carbohydrates that L. pentosus converts to lactate. This substrate route enables LAB metabolism in the membrane reactor; it does not make fungal hydrolysis alone sufficient for the observed redox state.
Evidence
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PMID:32855308 - SUPPORT (IN_VITRO)"We developed a versatile consortium-based strategy for the direct conversion of lignocellulose to short-chain fatty acids, which included the funneling of the lignocellulosic carbohydrates to lactate as a central intermediate in engineered food chains"
Lactate Supply and Redox Facilitation
CROSS_FEEDINGL. pentosus funnels carbohydrates to lactate and supplies acetate when metabolizing pentoses. Fungal oxygen consumption first lowers dissolved oxygen; subsequent LAB inoculation lowers redox potential further, enabling the obligate anaerobe. The membrane configuration, continuing fungal activity and LAB contribution work jointly: LAB alone cannot maintain anoxia. This supports resource and redox facilitation, not demonstrated reciprocal thermodynamic syntrophy.
Source Taxon: Lactobacillus pentosus
Target Taxon: Clostridium tyrobutyricum
Metabolites: glucose (CHEBI:17234 · MediaIngredientMech · CMMMech), lactate (CHEBI:24996 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- lactate biosynthetic process (GO:0019249 · PathwayMech)
- fermentation (GO:0006113 · PathwayMech)
L. pentosus supplies lactate and contributes to reducing conditions that enable C. tyrobutyricum co-fermentation. Acetate or glucose must also be available; acetate depletion and feed-rescue experiments support this requirement. Neither lactate alone nor LAB-alone oxygen removal is sufficient.
Evidence
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PMID:32855308 - PARTIAL (IN_VITRO)"A spatial niche enabled in situ cellulolytic enzyme production by an aerobic fungus next to facultative anaerobic lactic acid bacteria and the product-forming anaerobes"
Butyrate Production by Lactate-Acetate Co-fermentation
C. tyrobutyricum converts lactate with a co-substrate to butyrate. Lactate alone is insufficient: acetate depletion stops utilization, and acetate addition restores it; glucose can also serve as co-substrate. These experiments support the recipient conversion, not an exclusive source of every acetate molecule. Acetate feed, lower oxygen transfer and addition of L. brevis are separate experimental arms. The three-member consortium produced the reported beechwood yield after steam pretreatment; the four-member arm is not that benchmark.
Participating Taxa: Clostridium tyrobutyricum
Metabolites: lactate (CHEBI:24996 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), butyrate (CHEBI:17968 · MediaIngredientMech · CMMMech)
Biological Processes:
- butyrate metabolic process (GO:0019605 · PathwayMech)
- lactate catabolic process (GO:1903457 · PathwayMech)
Evidence
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PMID:32855308 - SUPPORT (IN_VITRO)"Clostridium tyrobutyricum, Veillonella criceti, or Megasphaera elsdenii were integrated into the lactate platform to produce 196 kilograms of butyric acid per metric ton of beechwood"
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PMID:32855308 - SUPPORT (IN_VITRO)"lactic acid cannot serve as a sole carbon source but must be co-consumed with either glucose or acetic acid"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How are oxygen uptake and carbon flux partitioned among members under each feed and oxygen-transfer condition?
The source supports fungal oxygen consumption, additional LAB-associated redox lowering and acetate-dependent lactate utilization. These controls do not establish exclusive partner-specific fluxes or reciprocal thermodynamic syntrophy. Keep acetate-feed, low-OTR and L. brevis arms separate. Non-graph pretreatment and gradient metadata remain issue #1904.
Attaches to: ecological_interactions#Cellulose Hydrolysis to Soluble Sugars, ecological_interactions#Lactate Supply and Redox Facilitation, ecological_interactions#Butyrate Production by Lactate-Acetate Co-fermentation
1 evidence item(s)
A spatial niche enabled in situ cellulolytic enzyme production by an aerobic fungus next to facultative anaerobic lactic acid bacteria and the product-forming anaerobes
Abstract supports spatial coexistence; accepted manuscript main text and Fig.S3 distinguish fungal oxygen consumption from the additional LAB-associated redox decrease. SI physiology discussion argues that LAB alone cannot sustain anoxia. The abstract is not itself an oxygen-flux partition experiment.
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Oxygen gradient | aerobic to anaerobic | N/A |
| Inoculation scheme | sequential (T. reesei → L. pentosus → C. tyrobutyricum) | N/A |
| Substrate | lignocellulosic biomass (beechwood) | N/A |
| Product yield | 196 kg butyric acid per metric ton beechwood | N/A |
Growth Media
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