Incidência de fungos dos gêneros Aspergillus e Penicillium em diferentes genótipos de castanha do brasil e avaliação dos óleos fixos no controle de Aspergillus flavus produtor de aflatoxinas

Abstract

Brazil nuts represent the subsistence form of many families in the Amazon region. Extraction, processing and storage are important critical control points in production. Due to the substrate and climatic conditions of the region favorable to the development of aflatoxigenic fungi and consequently the production of aflatoxins, it is necessary to study the mycobiota present in the nuts. The use of natural agents in the control of these species becomes fundamental, since Brazil nuts are considered an organic product. In order to evaluate the distribution of Aspergillus and Penicillium species, as well as the toxigenic potential, samples of 5 different genotypes of Brazil nuts were collected in the state of Amazonas. The samples were analyzed by direct plating, and the fungi identified by morphological methods and toxigenic potential by the thin chromatography, species of the genus Aspergillus presented higher incidence than species of the genus Penicillium in all the genotypes, however there was no significant difference in the distribution of the species nor of isolates between the genotypes. The fatty acid profile of the different genotypes was evaluated by the gas chromatography technique, and differences were detected between the compounds determined in each genotype. When testing the antifungal activity of the extracted oils on the growth of A. flavus, a significant difference was observed between the genotypes and the concentrations. Considering the use of chestnut oil as a natural agent in the control of A. flavus growth, all evaluated genotypes obtained a certain concentration, effectiveness. Among the results obtained we can observe the difference in the fatty acid profile, being genotypes 1 and 4, 5 and 3 grouped by similarity in the composition and the genotype 2 presented a different profile of the other genotypes. Genotypes 1, 3 and 5 presented henecosanoic acid as the major compound, genotype 2 tridecanoic acid and genotype 4 linolenic acid. There was a statistical difference in the inhibition halos formed each by genotype, with genotypes 1 and 2 greater inhibition halos than genotypes 3 and 5 and both larger halos than oil extracted from genotype 4. Concentration interfered with the growth of Aspergillus flavus, with concentrations of 250 μl, 62.5 μl, 7.81 μl, 3.91 μl more efficient than the concentrations of 125 μl, 31.25 μl and 15.63 μl and all other concentrations effective than the 500 μl concentration. The results obtained reinforce the need for studies of these compounds alone in order to identify which compost may have exerted greater antifungal activity.