Mesophilic · Extended-panel species

Penicillium roqueforti

Commercial blue-cheese starter culture and weak-acid-tolerant cereal spoilage species. Documented mycophenolic acid producer in moisture-damaged buildings.

Extended panelMesophilic · Aw ≥ 0.83

Moisture niche · where this species can grow

XerophilicAw < 0.80
MesophilicAw 0.80–0.89
HydrophilicAw ≥ 0.90
Min Aw 0.83
← Drier conditions toleratedRequires liquid water →
Minimum Aw
0.83
EPA reference (GM)
< 0.4 SE/mgMeklin AHHS threshold
Mycotoxin profile
6+ documented
Ecological role
Secondary colonizer

The < 0.4 SE/mg reference value is Meklin 2004's AHHS exclusion threshold: the paper retained species whose geometric mean was at least 2 spores per 5 mg dust (≈ 0.4 spores/mg) and eliminated the rest. This species was measured across the 1,096-home AHHS sample and characterized below that threshold, used here as a conservative ceiling on its true GM, not a percentile band. A detected value of X SE/mg implies an elevation factor of at least X ÷ 0.4 over the EPA reference, a lower bound, since the true GM is below 0.4. See the 82-species story for the math.

About Penicillium roqueforti

Penicillium roqueforti is best known commercially as the starter culture for Roquefort, Stilton, Gorgonzola, and other blue-veined cheeses. Outside cheese production it is a cereal-product spoilage organism (particularly of rye bread) that tolerates weak-acid preservatives, low oxygen (it grows in 0.5% O₂), and pH as low as ~2–3 (with a canonical growth range of pH 3.0–10.5). The species has a documented building-mycology footprint as a producer of mycophenolic acid in moisture-damaged buildings.

Taxonomy

Penicillium subgenus Penicillium, series Roqueforti

Ecology and habitat

P. roqueforti is a generalist saprophyte with an unusually broad tolerance profile: weak-acid preservatives, low oxygen, and low pH conditions (canonical growth range pH 3.0–10.5; with extreme tolerance to ~2 in some conditions) that exclude most fungal competitors. This tolerance underpins both its commercial use (it survives the curing environment of blue cheese) and its niche in spoilage and indoor environments.

Indoor relevance

The species is documented in moisture-damaged buildings, where it produces mycophenolic acid, the same molecule used clinically as an immunosuppressant in transplant medicine, occurring in indoor air as a fungal secondary metabolite. P. roqueforti's indoor relevance is principally this MPA emission route, shared with Penicillium brevicompactum on the standard 36-species ERMI panel.

Cardinal physiology

Minimum water activity for conidial germination: Aw 0.83 (Kalai et al. 2017)[2]. Growth across −2 to 35 °C with optimum at 26.9 °C[2]. The unusual tolerances (weak acids, low O₂, pH down to ~2) distinguish P. roqueforti from most other Penicillia and underpin its commercial cheese-culture use.

Tolerant of weak-acid preservatives and low oxygen; cool-storage spoilage organism.

Secondary metabolites

The mycotoxin profile is broad: roquefortine C (a neurotoxic alkaloid produced abundantly in cheese), mycophenolic acid (immunosuppressant), PR toxin, andrastin A, eremofortins, and isofumigaclavines. Mycophenolic acid is the same molecule used clinically as the prodrug mycophenolate mofetil for transplant-rejection prevention. This is one of the few places in indoor mycology where the species's secondary metabolite has a directly characterized human pharmacology, because the molecule's identity is the same in environmental and pharmaceutical contexts.

Compounds documented as produced by Penicillium roqueforti (presence and quantity vary by chemotype, strain, and substrate):

Roquefortine C (neurotoxin)Mycophenolic acid (immunosuppressant)PR toxinAndrastin AEremofortinsIsofumigaclavines

DNA-based detection of a mycotoxin-producing species in household dust does not directly establish exposure to that mycotoxin at any specific concentration.

Lab availability

Some commercial dust testing labs offer this species as an extended-panel option. Specific lab coverage changes over time: check with your laboratory for current panel options.

Related

Mycophenolic acidDocumented building-derived metabolite of this species.Penicillium brevicompactumStandard-ERMI relative; other major indoor MPA producer.Penicillium speciesBeyond the 36

References

  1. Meklin T, Haugland RA, Reponen T, Varma M, Lummus Z, Bernstein D, Wymer LJ, Vesper SJ. Quantitative PCR analysis of house dust can reveal abnormal mold conditions. J Environ Monit. 2004;6(7):615–620.
  2. Kalai S, Anzala L, Bensoussan M, Dantigny P. Modelling the effect of temperature, pH, water activity, and organic acids on the germination time of Penicillium camemberti and Penicillium roqueforti conidia. Int J Food Microbiol. 2017;240:124–130.
  3. Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.