Effects of trace elements on growth and aflatoxin production of Aspergillus flavus
1988
Park, J.M. (Rural Development Administration, Anyang (Korea R.). Veterinary Research Institute) | Han, S.N. (Seoul National Univ., Suwon (Korea R.). Coll. of Veterinary Medicine)
Aflatoxins inducing animal aflatoxicosis are a mixture of toxic secondary metabolites produced from certain strains of Aspergillus flavus and A. parasiticus. Aflatoxin production of fungus is highly influenced by various factors such as moisture content, temperature and nutrients including trace minerals that are required for fungal growth. This study is aimed to follow the effects of the trace elements such as zinc, copper, manganese, iron, molybdenum and boron on the growth and aflatoxin production of A. flavus in the defined medium devoid of each of the above elements. Fungal growth and aflatoxin production were evaluated by the determination of mycelial dry weight and the quantitation by thin layer chromatography-densitometry, respectively. When manganese was depleted from the medium, the gel like colony was submerged and the mycelial dry weight was decreased to 0.7437g in contrast with 3.2690g in non depleted medium (p0.01). Zinc depletion resulted in poor aflatoxin production in cultured medium. When zinc was depleted, the aflatoxin concentration of cultured medium was 0.15 ppm, in contrast with 31.29 ppm in non depleted medium (p0.01). A similar tendency was observed in the case of corn culture. Copper was responsible to form green pigment in A. flavus colony but the color was yellow when it was depleted from the medium. The least total aflatoxin content, distributed in the cultured medium and mycelium, was observed in case of copper deficiency. The distribution of aflatoxin in the medium and mycelium cultured with all the six elements were 19.89 and 89.94 ppm, respectively. However in the case of zinc depletion the mycelium contained 23.39 ppm of aflatoxin but no toxin in cultured medium. This suggested that aflatoxin, biosynthesized in the mycelium, may be excreted into the medium under the favor of zinc. Aflatoxins, produced in glucose-mineral medium where Mn was supplemented and heated at 121deg C for 15 minutes, appeared in two spots of B2 and G2. While in the medium with same condition but Mn depleted appeared four spots of B1, B2, G1 and G2
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