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Published on: April 23, 2012
In vitro cytotoxicity of fungi spoiling maize silage
R R Rasmussen1, P H Rasmussen, T O Larsen
1Department of Food Chemistry, National Food Institute, Technical University of Denmark, Søborg, Denmark. riro@food.dtu.dk
Abstract:
Penicillium roqueforti, Penicillium paneum, Monascus ruber, Alternaria tenuissima, Fusarium graminearum, Fusarium avenaceum, Byssochlamys nivea and Aspergillus fumigatus have previously been identified as major fungal contaminants of Danish maize silage. In the present study their metabolite production and in vitro cytotoxicity have been determined for fungal agar and silage extracts. All 8 fungal species significantly affected Caco-2 cell viability in the resazurin assay, with large variations for each species and growth medium. The 50% inhibition concentrations (IC(50)) of the major P. roqueforti metabolites roquefortine C (48 μg/mL), andrastin A (>50 μg/mL), mycophenolic acid (>100 μg/mL) and 1-hydroxyeremophil-7(11),9(10)-dien-8-one (>280 μg/mL) were high. Fractionating of agar extracts identified PR-toxin as an important cytotoxic P. roqueforti metabolite, also detectable in maize silage. The strongly cytotoxic B. nivea and P. paneum agar extracts contained patulin above the IC(50) of 0.6 μg/mL, however inoculated onto maize silage B. nivea and P. paneum did not produce patulin (>371 μg/kg). Still B. nivea infected maize silage containing mycophenolic acid (∼50 mg/kg), byssochlamic acid and other metabolites, was cytotoxic. In contrast hot-spots of P. roqueforti, P. paneum, M. ruber and A. fumigatus were not more cytotoxic than uninoculated silage.
Insights
Eight fungal species contaminate Danish maize silage, with varying in vitro cytotoxicity. Byssochlamys nivea and Penicillium paneum produced cytotoxic metabolites in silage, even without patulin.
Area of Science:
- Mycology
- Food Safety
- Toxicology
Background:
- Danish maize silage is frequently contaminated with fungi including Penicillium roqueforti, Penicillium paneum, Monascus ruber, Alternaria tenuissima, Fusarium graminearum, Fusarium avenaceum, Byssochlamys nivea, and Aspergillus fumigatus.
- Understanding the metabolite production and cytotoxicity of these fungal contaminants is crucial for assessing silage safety.
Purpose of the Study:
- To determine the metabolite production and in vitro cytotoxicity of eight major fungal contaminants found in Danish maize silage.
- To identify specific mycotoxins responsible for cytotoxicity in fungal extracts and infected silage.
Main Methods:
- Fungal species were cultured on agar and inoculated onto maize silage.
- Cytotoxicity was assessed using the resazurin assay on Caco-2 cells.
- Metabolite production was analyzed in both agar and silage extracts.
Main Results:
- All eight fungal species demonstrated significant cytotoxicity against Caco-2 cells, with considerable variation.
- Penicillium roqueforti metabolites like roquefortine C and PR-toxin showed cytotoxicity, with PR-toxin detected in silage.
- Byssochlamys nivea and Penicillium paneum produced cytotoxic silage containing mycophenolic acid and byssochlamic acid, despite not producing patulin in silage.
Conclusions:
- Fungal contaminants in maize silage pose a cytotoxic risk, with specific metabolites contributing to this effect.
- The cytotoxic potential of B. nivea and P. paneum in silage is linked to metabolites other than patulin.
- Localized contamination by certain fungi (P. roqueforti, P. paneum, M. ruber, A. fumigatus) did not increase silage cytotoxicity.
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