identifier: traitmech:000179
label: butyric acid fermentation
definition: A fermentation in which anaerobic bacteria convert organic substrates
  to butyrate as a major reduced end product while conserving energy by substrate-level
  phosphorylation or ion-gradient generation.
definition_source: DOI:10.1111/j.1574-6968.2009.01514.x
trait_category: METABOLISM
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1002005
synonyms:
- synonym_text: butyrate fermentation
  synonym_type: RELATED_SYNONYM
  source: DOI:10.1111/j.1574-6968.2009.01514.x
evidence:
- reference: DOI:10.3389/fmicb.2021.703525
  snippet: Until about 10 years ago, anaerobes were thought to exclusively use substrate
    level phosphorylation (SLP), by which only part of the available energy could
    be conserved. Therefore, anaerobes were regarded as unproductive and inefficient
    energy conservers. The discovery of electrochemical Na+ gradients generated by
    biotin-dependent decarboxylations or by reduction of NAD+ with ferredoxin changed
    this view.
  notes: Buckel supplies anaerobic-fermentation energy-conservation context, including
    substrate-level phosphorylation and ferredoxin-linked ion-gradient generation.
- reference: DOI:10.1111/j.1574-6968.2009.01514.x
  snippet: 'Five different arrangements have been identified for the genes of the
    central pathway involved in butyrate synthesis, while in most cases butyryl-CoA
    : acetate CoA-transferase, rather than butyrate kinase, appears to perform the
    final step in butyrate synthesis. Mechanisms have been proposed recently in non-gut
    Clostridium spp. whereby butyrate synthesis can result in energy generation via
    both substrate-level phosphorylation and proton gradients.'
  notes: 'Louis and Flint connect butyrate synthesis to energy generation through
    substrate-level phosphorylation and proton gradients while reviewing the butyryl-CoA
    : acetate CoA-transferase terminal route.'
- reference: DOI:10.1111/1751-7915.12304
  snippet: the adapted C. tyrobutyricum strain was characterized by a high yield and
    selectivity to butyric acid
  notes: Baroi et al. directly studied butyric acid fermentation from pretreated and
    hydrolysed wheat straw by an adapted Clostridium tyrobutyricum strain.
canonical_examples:
- taxon_id: NCBITaxon:1519
  taxon_label: Clostridium tyrobutyricum
  note: Butyric-acid fermenter used by Baroi et al. for fermentative conversion of
    wheat-straw hydrolysate to butyric acid.
  reference: DOI:10.1111/1751-7915.12304
discussions:
- discussion_id: butyric-acid-fermentation-xref-gap
  prompt: Resolve an exact external ontology class for butyric acid fermentation before
    adding a TraitRecord xref.
  kind: CURATION_TODO
  status: OPEN
  rationale: No exact GO or external metabolism class was resolved for the organism-level
    butyrate-producing fermentation phenotype; butyrate-synthesis enzyme molecular
    functions and chemical production relations are shifted relative to this product-specific
    fermentation class.
  posed_by: codex
  posed_date: '2026-09-14'
curation_history:
- timestamp: '2026-09-14T01:34:38Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Minted butyric acid fermentation as a DOI-backed product-specific fermentation
    TraitRecord after a repository-wide duplicate review covering ignored and hidden
    files; METPO has no exact butyric acid fermentation class yet and the placeholder
    is reserved in proposals/metpo_traitmech_v56.
  llm_assisted: true