Aflatoxin formation and the dual phenomenon in Aspergillus flavus Link
Abstract:
Trials were performed with three aflatoxin-forming isolates of Aspergillus flavus from formic acid-treated materials containing aflatoxin, one A. flavus strain isolated from mouldy barley kept for two months in an anaerobic jar and one non-toxic A. flavus strain from the culture collection at our Department. The non-toxic strain and one aflatoxin producer were cultured in salts-sugar-asparagine substrate (SLM) for aflatoxin production and in a specially prepared grass substrate (GS). Formic acid and ammonium formate were added to both substrates, and sucrose in a low amount was added to the grass substrate. The aflatoxin-forming isolate segregated on the grass substrate into two different lines, one with high aflatoxin production and one with very low aflatoxin-forming ability, higher growth rate and reduced sporulation, on the SLM substrate. When exposed to sucrose in grass substrate and ammonium formate in SLM, one toxic and one non-toxic strain were provoked to increased aflatoxin formation. The A. flavus isolate from the anaerobic jar also segregated on the grass substrate, and these segregants were more sensitive to a high dose of formic acid. In these A. flavus strains three seems to be a continuous variation between different lines, depending on cultivation conditions. In the two aflatoxin-forming isolates left, such segregation tendencies were not very marked on any substrate.
Insights
Cultivation conditions significantly influence aflatoxin production in Aspergillus flavus. Environmental factors like formic acid and sucrose can alter fungal toxin-forming capabilities and segregation.
Area of Science:
- Mycology
- Food Safety
- Microbial Genetics
Background:
- Aflatoxins are toxic secondary metabolites produced by Aspergillus flavus.
- Environmental factors can influence aflatoxin biosynthesis in fungi.
- Understanding variability in aflatoxin production is crucial for food safety.
Purpose of the Study:
- To investigate the impact of cultivation conditions on aflatoxin production in Aspergillus flavus.
- To examine the segregation of aflatoxin-producing and non-producing strains under varying substrates and chemical treatments.
- To assess the influence of formic acid, ammonium formate, and sucrose on aflatoxin biosynthesis.
Main Methods:
- Culturing of Aspergillus flavus isolates (toxic and non-toxic) on salts-sugar-asparagine substrate (SLM) and grass substrate (GS).
- Addition of formic acid, ammonium formate, and sucrose to substrates.
- Analysis of aflatoxin production, growth rate, and sporulation in different fungal lines and segregants.
Main Results:
- Aflatoxin-producing isolates segregated on grass substrate, yielding high and low producers with altered growth and sporulation.
- Exposure to sucrose and ammonium formate induced increased aflatoxin formation in both toxic and non-toxic strains.
- Isolates from anaerobic conditions showed segregation and increased sensitivity to formic acid.
Conclusions:
- Cultivation conditions, including substrate composition and chemical additives, induce significant variation in aflatoxin production and fungal traits within Aspergillus flavus.
- Environmental manipulation can provoke or suppress aflatoxin biosynthesis, highlighting the plasticity of these fungi.
- Further research is needed to understand the genetic and environmental interplay governing aflatoxin production in Aspergillus flavus.
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