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Aflatoxigenic Potential for Aspergilli on sucrose substrates
Abstract:
Sucrose concentrations of 3, 10, 20, and 30% in Czapek Dox broth served as the carbon source for growth, aflatoxin production, and sporulation for Aspergillus parasiticus NRRL 2999 and A. flavus NRRL 3557, 5862, and 5013. All cultures produced mycelial growth and sporulated in all sucrose concentrations during the 12-day growth period. The area of mycelial mat coverage per hour increased directly with increased sugar concentrations. The 20 and 30% sucrose concentrations inhibited mycelial growth for 5862. The 30% sucrose cultures of 3557 and 5862 failed to produce detectable levels of aflatoxins. All other isolates produced B1 and G1 in an approximately 4:1 ratio in all sucrose concentrations. Only 2999 was a substantial producer of aflatoxin in all 4 sucrose cultures, ranging from 72 to 96 micrograms/mL medium. A. flavus 5013 produced the most toxin, 144 and 126 micrograms/mL medium in the 10 and 20% sucrose cultures, respectively. The 10 and 20% sucrose cultures were most conducive to aflatoxin production. Since these sucrose levels correspond closely to the levels in many food and drink products, especially home-made products, care and attention should be taken to keep them free of aflatoxigenic spores. Extensive mycelial growth and sporulation, even in aflatoxigenic strains, do not necessarily result in comparably high aflatoxin levels. Routine extraction and quantitation procedures for aflatoxin were applicable and provided satisfactory results.
Insights
Higher sucrose concentrations can impact Aspergillus growth and aflatoxin production. Optimal aflatoxin levels were observed at 10-20% sucrose, highlighting food safety concerns.
Area of Science:
- Food Microbiology
- Mycotoxicology
- Plant Pathology
Background:
- Aspergillus species are significant foodborne pathogens.
- Aflatoxins produced by Aspergillus are potent carcinogens.
- Sucrose is a common carbon source influencing fungal growth and toxinogenesis.
Purpose of the Study:
- To investigate the effect of varying sucrose concentrations on Aspergillus parasiticus and Aspergillus flavus growth, sporulation, and aflatoxin production.
- To determine optimal sucrose levels for aflatoxin biosynthesis in selected Aspergillus strains.
Main Methods:
- Aspergillus parasiticus NRRL 2999 and Aspergillus flavus strains (NRRL 3557, 5862, 5013) were cultured in Czapek Dox broth with 3%, 10%, 20%, and 30% sucrose.
- Mycelial growth, sporulation, and aflatoxin (B1 and G1) production were monitored over 12 days.
- Aflatoxin levels were quantified using routine extraction and quantitation procedures.
Main Results:
- All strains exhibited mycelial growth and sporulation across all sucrose concentrations.
- Mycelial coverage increased with sucrose concentration, though 20-30% inhibited growth in strain 5862.
- Aflatoxin production was significantly reduced or undetectable at 30% sucrose for strains 3557 and 5862.
- The 10% and 20% sucrose concentrations were most conducive to aflatoxin production, with strain 5013 yielding the highest levels (144 and 126 µg/mL).
- Strain 2999 was a consistent producer across all concentrations (72-96 µg/mL).
Conclusions:
- Sucrose concentration critically influences aflatoxin biosynthesis in Aspergillus species.
- 10-20% sucrose levels promote significant aflatoxin production, posing a risk in food products with similar sugar content.
- High mycelial growth and sporulation do not always correlate with high aflatoxin levels.