A defined three-strain lactic-acid-bacterial triculture assembled from Parmigiano Reggiano natural whey starter isolates. Cristofolini et al. 2026 combined Lactobacillus helveticus LBB04, Streptococcus thermophilus C001.27, and Lactobacillus delbrueckii subsp. lactis C5I3 in a 1:1:1 milk triculture to test whether natural-whey-starter partners could enhance the impaired cultivability and acidification activity of L. delbrueckii subsp. lactis. Across the milk cross-feeding panel, tricultures showed the highest maximum acidification rates and total lactic acid production, with positive S. thermophilus-linked effects and weaker L. helveticus/L. delbrueckii pair performance in set 2.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
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| Lactobacillus helveticus LBB04 — ontology label: Lactobacillus helveticus | NCBITaxon:1587 · TaxonMech · TraitMech | N/A | |
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| Streptococcus thermophilus C001.27 — ontology label: Streptococcus thermophilus | NCBITaxon:1308 · TaxonMech · TraitMech | N/A | |
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| Lactobacillus delbrueckii subsp. lactis C5I3 — ontology label: Lactobacillus delbrueckii subsp. lactis | NCBITaxon:29397 · TaxonMech · TraitMech | 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.
Set 2 milk acidification enhancement
The set 2 LBB04/C001.27/C5I3 triculture produced higher total lactic acid than the tested monocultures and pairwise cultures. Maximum acidification rate was high, but the exact set 2 C001.27/C5I3 pair was comparable to the triculture, so the triculture was not uniquely superior on this rate readout. Total inoculum was held constant across compositions. These positive community fermentation phenotypes do not establish per-strain growth, reciprocal benefit or a specific molecular exchange.
Metabolites: lactate (CHEBI:24996 · MediaIngredientMech · CMMMech)
Biological Processes:
- fermentation (GO:0006113 · PathwayMech)
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:41859451 - SUPPORT (IN_VITRO)"Across all inoculation sets, tri-cultures consistently displayed the highest μmax values (p < 0.05), followed by the co-cultures St + Lh and St + Ld."
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PMID:41859451 - SUPPORT (IN_VITRO)"Across all three strain combinations, total lactic acid production was highest in tri-cultures, followed by St + Lh and St + Ld co-cultures (p < 0.05)"
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PMID:41859451 - SUPPORT (IN_VITRO)"co-cultivation of St strain C001.27 with Ld strain C5I3 resulted in μmax values comparable to those observed under tri-culture conditions."
C001.27-C5I3 acidification enhancement
The C001.27/C5I3 pair had a higher maximum acidification rate than either corresponding monoculture, and in set 2 its rate was comparable to that of the triculture. This is a positive two-member fermentation phenotype, not proof that adding LBB04 preserves a pair-specific causal mechanism or that both members benefit equally. The study interprets D-lactate predominance as preferential L. delbrueckii activity; exchanged formate, folate and peptides were not directly resolved in this assay.
Participating Taxa: Streptococcus thermophilus C001.27, Lactobacillus delbrueckii subsp. lactis C5I3
Biological Processes:
- fermentation (GO:0006113 · PathwayMech)
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
-
PMID:41859451 - SUPPORT (IN_VITRO)"co-cultivation of St strain C001.27 with Ld strain C5I3 resulted in μmax values comparable to those observed under tri-culture conditions"
LBB04-C5I3 reduced acidification subset
The LBB04/C5I3 pair showed lower maximum acidification rates than the corresponding monocultures and the C001.27/C5I3 pair. Its total lactic acid was also lower than the triculture and St-containing pairs, with D-lactate comprising 75.95% of the pair’s total lactate. Preserve this negative fermentation response without converting bulk acidification to a strain-specific growth-inhibition assay or claiming a measured antimicrobial or nutrient-competition mechanism.
Participating Taxa: Lactobacillus helveticus LBB04, Lactobacillus delbrueckii subsp. lactis C5I3
Biological Processes:
- fermentation (GO:0006113 · PathwayMech)
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
-
PMID:41859451 - SUPPORT (IN_VITRO)"co-cultivation with Lh strain LBB04 yielded significantly lower μmax values compared to the corresponding St + Ld interaction"
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PMID:41859451 - SUPPORT (IN_VITRO)"In inoculation sets 2 and 3, Lh + Ld co-cultures yielded significantly lower total lactic acid than tri-cultures and the St + Lh and St + Ld co-cultures"
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PMID:41859451 - SUPPORT (IN_VITRO)"co-inoculation of milk with Lh and Ld resulted in reduced acidification rates compared with the corresponding monocultures"
Set 2 Triculture D-Lactate Accumulation
At the end of fermentation, set 2 triculture D-lactate was significantly higher than in the C5I3 monoculture. This is a measured mixed-culture pool, consistent with L. delbrueckii metabolic activity but not exclusive C5I3 production or directly measured C5I3 cell growth. L. helveticus produces both enantiomers, and C001.27 monoculture was 83% L-lactate rather than exclusively L-lactate. Acidification and lactate are related readouts; an arrow from acidification to inferred member activity would reverse measurement and inference.
Metabolites: lactate (CHEBI:24996 · MediaIngredientMech · CMMMech)
Biological Processes:
- fermentation (GO:0006113 · PathwayMech)
Evidence
-
PMID:41859451 - SUPPORT (IN_VITRO)"In two of the three sets (sets 1 and 2), D-lactate levels in tri-cultures were significantly higher than those detected in the corresponding Ld monocultures (p < 0.05)"
Knowledge gaps & discussions (2)
KNOWLEDGE_GAP OPEN Which exchanged metabolites or inhibitory molecules specifically explain the C001.27/C5I3 stimulation and LBB04/C5I3 weaker pairwise acidification in the Parmigiano Reggiano natural-whey-starter set 2 assays?
PMID:41859451 directly measured acidification and D-/L-lactate outcomes for monocultures, pairwise co-cultures, and tricultures, but the source's formate, folate, urease, NADH oxidase, and antimicrobial-molecule explanations are literature-backed hypotheses rather than molecule-level measurements in this exact set 2 community.
Attaches to: ecological_interactions#C001.27-C5I3 acidification enhancement, ecological_interactions#LBB04-C5I3 reduced acidification subset
KNOWLEDGE_GAP OPEN Which member-resolved processes explain the positive and negative fermentation responses?
Four measured phenotypes remain. Pair and triculture comparisons do not form a causal sequence, and higher D-lactate is an observation used to infer activity, not an outcome caused by measuring acidification. No new mediator arrows are justified by the full main text. Preserve previous #1077-1079 removal of unsupported mutualism, taxon roles and exclusive C5I3 attribution; the existing molecular-mechanism gap remains open.
Attaches to: ecological_interactions#Set 2 milk acidification enhancement, ecological_interactions#C001.27-C5I3 acidification enhancement, ecological_interactions#LBB04-C5I3 reduced acidification subset, ecological_interactions#Set 2 Triculture D-Lactate Accumulation
1 evidence item(s)
co-cultivation of St strain C001.27 with Ld strain C5I3 resulted in μmax values comparable to those observed under tri-culture conditions.
Exact set 2 exception to a uniquely highest triculture rate.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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PubMed - Parmigiano NWS Set 2 LAB triculture
PubMed record for the Frontiers in Microbiology article describing milk cross-feeding among L. helveticus, L. delbrueckii subsp. lactis, and S. thermophilus natural-whey-starter isolates. |
OTHER | PMID:41859451 |
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DOI - Parmigiano NWS microbial interactions
DOI landing page for the Frontiers in Microbiology article describing Parmigiano Reggiano natural-whey-starter LAB cross-feeding assays. |
OTHER | doi:10.3389/fmicb.2026.1755652 |
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