Effect of metal ions on aflatoxin production byAspergillus parasiticus

Abstract

The effect of iron, copper, cobalt, cadmium, zinc, molybdenum, magnesium and manganese salts was studied on aflatoxin production in relation to mycelial mass. Iron, copper and cadmium salts decreased the aflatoxin production to different levels but a mixed trend was observed depending on salt concentration, with molybdenum, magnesium and manganese. Cobalt and zinc salts stimulated aflatoxin production at all concentrations studied. The maximum increase in aflatoxin production, 655% and 519% was observed in the presence of zinc sulfate and sodium molybdate, respectively. A negative correlation was observed between aflatoxin production and vegetative growth of fungus.

Biosynthesis of aflatoxin—the role of nutritional factors

“…Maggon et al (1973) observed inhibition of aflatoxin synthesis at low levels of manganese in the medium whereas higher levels resulted in enhanced aflatoxin formation but at some intermediate concentrations of manganese, there was no effect on aflatoxin biosynthesis. A mixed trend was also reported by Tiwari et al (1986): stimulation with 0.2, 0.5 and 1.2 mmol I-' and inhibition with 0.7 mmol 1of manganous chloride. However, when manganous sulphate was used aflatoxin production decreased despite the concentration.…”

“…1967). In contrast to Davis et al (1967) andMaggon et al (1973), Tiwari et al (1986) reported inhibition of aflatoxin production by iron salts. Maggon et al (1973) pointed out that the protein binding activity of different metals is, in decreasing order, Cu, Zn, Co, Fe, Mn and Ca which corresponded roughly with the ability of the trace metal ions to stimulate aflatoxin production observed in their study.…”

“…In general the type of response of a given mineral on aflatoxin production is dependent on its concentration, on the kind of salt (in relation to the associated anion) in which the metal is supplied (Tiwari et al 1986) and the time at which a metal is added to the fungal culture (Coupland and Niehauz 1987).…”

“…The level of cAMP is supposed to be regulated by the intracellular amount and/or transport of glucose and is not determined by the extracellular glucose concentration (Zonneveld 1976). In Aspergillus nidulans manganese deficiency had a definite effect on cAMP levels and external glucose played only an indirect role (Zonneveld 1976). Tiwari et al (1986 observed a different response to aflatoxin production depending on salt concentration with molybdenum and magnesium.…”

Mycotoxins of Aspergillus and other filamentous fungi

“…1984). In a completely zinc-limited medium, cadmium ions will stimulate growth and versicolorin production in a mutant strain of A. parasiticus (Failla & Niehaus 1986) although Tiwari et al (1986a) reported that CdZ+ repressed aflatoxin production. It is not unusual to find apparently conflicting reports in the literature about secondary metabolite studies and they reflect the need for very careful descriptions of experimental method-A number of filamentous fungi can produce ethylene and it seems that A .…”