identifier: traitmech:000028
label: ethanol fermentation
definition: A fermentation in which pyruvate is decarboxylated to acetaldehyde (releasing
  CO2) and then reduced by NADH to ethanol, regenerating NAD+ for glycolysis. Characteristic
  of yeasts and the bacterium Zymomonas mobilis.
definition_source: DOI:10.3389/fmicb.2021.703525
trait_category: METABOLISM
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1002005
synonyms:
- synonym_text: alcoholic fermentation
  synonym_type: RELATED_SYNONYM
  source: DOI:10.3390/molecules31020333
evidence:
- reference: DOI:10.3390/molecules31020333
  notes: Review of classical fermentations describes the alcoholic (ethanol) pathway
    in which pyruvate is decarboxylated and reduced to ethanol.
- reference: DOI:10.3389/fmicb.2021.703525
  notes: Review of fermentative energy conservation supports ethanol as an NADH-reoxidizing
    fermentation end product.
canonical_examples:
- taxon_id: NCBITaxon:542
  taxon_label: Zymomonas mobilis
  note: "Canonical bacterial ethanologen (Entner-Doudoroff route to ethanol)."
  reference: PMID:27629544
causal_graphs:
- graph_id: ethanol_fermentation_pyruvate_to_ethanol
  title: Ethanol (alcoholic) fermentation converts pyruvate to ethanol + CO2
  description: Evidence-backed causal sketch linking pyruvate decarboxylation and
    NADH-driven ethanol production to NAD+ regeneration.
  nodes:
  - node_id: ethanol_fermentation_trait
    label: ethanol fermentation
    node_type: TRAIT
    grounding: traitmech:000028
    description: Alcoholic fermentation producing ethanol and CO2.
  - node_id: fermentation_process
    label: fermentation
    node_type: BIOLOGICAL_PROCESS
    grounding: GO:0006113
    description: ATP-yielding catabolism with organic terminal acceptors.
  - node_id: ethanol
    label: ethanol
    node_type: CHEMICAL
    description: Reduced end product regenerating NAD+ from NADH.
    grounding: CHEBI:16236
  - node_id: pyruvate
    label: pyruvate
    node_type: CHEMICAL
    description: Glycolytic end product decarboxylated in ethanol fermentation.
    grounding: CHEBI:15361
  - node_id: pyruvate_decarboxylase
    label: pyruvate decarboxylase
    node_type: GENE_OR_PROTEIN
    description: Enzyme (EC 4.1.1.1) decarboxylating pyruvate to acetaldehyde and
      CO2.
    grounding: UniProtKB:A0A067Z5Y9
  - node_id: acetaldehyde
    label: acetaldehyde
    node_type: CHEMICAL
    description: Intermediate produced from pyruvate and reduced to ethanol.
    grounding: CHEBI:15343
  - node_id: carbon_dioxide
    label: carbon dioxide
    node_type: CHEMICAL
    description: CO2 released during pyruvate decarboxylation.
    grounding: CHEBI:16526
  - node_id: alcohol_dehydrogenase
    label: alcohol dehydrogenase
    node_type: GENE_OR_PROTEIN
    description: Enzyme (EC 1.1.1.1) reducing acetaldehyde to ethanol using NADH.
    grounding: UniProtKB:A0A022L3Z7
  - node_id: nadh
    label: NADH
    node_type: CHEMICAL
    description: Reduced cofactor reoxidized during ethanol formation.
  - node_id: nad_plus
    label: NAD+
    node_type: CHEMICAL
    description: Oxidized cofactor regenerated to sustain glycolysis.
    grounding: CHEBI:15846
  edges:
  - subject: ethanol_fermentation_trait
    predicate: participates in
    object: fermentation_process
    description: Alcoholic fermentation is a class of fermentation metabolism.
    evidence:
    - reference: DOI:10.3389/fmicb.2021.703525
      notes: Energy-conservation review supports ethanol as an NADH-reoxidizing fermentation
        end product.
    predicate_id: biolink:participates_in
  - subject: ethanol_fermentation_trait
    predicate: produces
    object: ethanol
    description: Ethanol is the characteristic end product of the pathway.
    evidence:
    - reference: DOI:10.3390/molecules31020333
      notes: Classical-fermentation review describes pyruvate decarboxylation and
        reduction to ethanol.
    predicate_id: METPO:2000202
  - subject: pyruvate
    predicate: is substrate for
    object: pyruvate_decarboxylase
    description: Pyruvate is decarboxylated by pyruvate decarboxylase to acetaldehyde
      + CO2.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Pyruvate is decarboxylated to acetaldehyde by pyruvate decarboxylase
        (PDC), releasing CO2.
  - subject: pyruvate_decarboxylase
    predicate: produces
    object: acetaldehyde
    description: Pyruvate decarboxylase yields acetaldehyde from pyruvate.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Pyruvate is decarboxylated to acetaldehyde by pyruvate decarboxylase
        (PDC).
    predicate_id: METPO:2000202
  - subject: pyruvate_decarboxylase
    predicate: produces
    object: carbon_dioxide
    description: Decarboxylation of pyruvate releases CO2.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Pyruvate is decarboxylated to acetaldehyde by pyruvate decarboxylase
        (PDC), releasing CO2.
    predicate_id: METPO:2000202
  - subject: acetaldehyde
    predicate: is substrate for
    object: alcohol_dehydrogenase
    description: Acetaldehyde is reduced to ethanol by alcohol dehydrogenase.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Acetaldehyde is reduced to ethanol by alcohol dehydrogenase (ADH).
  - subject: alcohol_dehydrogenase
    predicate: produces
    object: ethanol
    description: Alcohol dehydrogenase produces ethanol from acetaldehyde.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Acetaldehyde is reduced to ethanol by alcohol dehydrogenase (ADH).
    predicate_id: METPO:2000202
  - subject: alcohol_dehydrogenase
    predicate: consumes
    object: nadh
    description: The ADH reduction step oxidizes NADH.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: ADH reaction reoxidizes NADH, regenerating NAD+ to sustain glycolysis.
    predicate_id: biolink:consumes
  - subject: alcohol_dehydrogenase
    predicate: produces
    object: nad_plus
    description: NAD+ is regenerated from NADH during ethanol formation, sustaining
      glycolysis.
    evidence:
    - reference: DOI:10.5376/be.2024.14.0025
      notes: Regenerating NAD+ from NADH to sustain glycolysis.
    predicate_id: METPO:2000202
curation_history:
- timestamp: '2026-05-30T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate METABOLISM trait (ethanol/alcoholic fermentation); product-specific
    sub-variant of the existing Fermentation class (METPO:1002005).
  llm_assisted: true
- timestamp: '2026-06-10T14:00:00Z'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added evidence-backed causal graph (alcoholic fermentation / ethanol production)
    with GO node grounding and METPO/biolink predicate groundings; promoted PROPOSED
    to REVIEWED.
  llm_assisted: true
- timestamp: '2026-06-14T06:55:38Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:16236×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 7 evidence-backed generic edges (7 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:12Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 5 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2000202×4, biolink:consumes×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:21:18Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:16526×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:32Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 3 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:15361×1, CHEBI:15343×1, CHEBI:15846×1).
  llm_assisted: true
- timestamp: '2026-06-26T07:15:18Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (UniProtKB:A0A067Z5Y9×1, UniProtKB:A0A022L3Z7×1).
  llm_assisted: true