Interaction of Wild Strains of Aspergilla with Aspergillus parasiticus ATCC15517 and Aflatoxin Production †

Aflatoxins are secondary metabolites produced by some competent mould strains of Aspergillus flavus, A. parasiticus and A. nomius. These compounds have been extensively studied with regards to their toxicity for animals and humans; they are able to induce liver cancer and may cause a wide range of adverse effects in living organisms. Aflatoxins are found as natural contaminants of food and feed; the main line of the strategy to control them is based on the prevention of the mould growth in raw vegetable or during its storage and monitoring of each crop batch. Mould growth is conditioned by many ecological factors, including biotic ones. Hazard characterization models for aflatoxins in crops must take into consideration biotic interactions between moulds and their potential effects on growth development. The aim of this work is to study the effect of the biotic interaction of 14 different wild strains of Aspergilla (different species), with a competent strain (Aspergillus parasiticus ATCC 15517) using an in vitro production model. The laboratory model used was a natural matrix (humidified cracked corn), on which each wild strain challenged the aflatoxin production of a producer strain. Cultures were incubated at 28 degrees C for 12 days and sampled at the 8(th) and 12(th). Aflatoxin detection and quantification was performed by HPLC using a procedure with a MRPL = 1 microg/kg. Results of those interactive cultures revealed both synergic and antagonistic effects on aflatoxin biosynthesis. Productivity increases were particularly evident on the 8(th) day of incubation with wild strains of A. flavipes (+ 70.4 %), A. versicolor (+ 54.9 %) and A. flavus 3 (+ 62.6 %). Antagonistic effects were found with A. niger (- 69.5%), A. fumigatus (- 47.6 %) and A. terreus (- 47.6 %) on the 12(th) day. The increased effects were more evident on the 8(th) of incubation and the decreases were more patent on the 12(th) day. Results show that the development of Aspergilla strains concomitantly with competent aflatoxin producing moulds has a significant influence on the natural biosynthesis pattern.