Effect of gamma radiation on ochratoxin production by the fungus Aspergillus ochraceus

Abstract

Mycelial discs of the fungus Aspergillus ochraceus NRRL 3174 were exposed to gamma irradiation and then incubated on synthetic medium (SM). Growth rate, mycelial dry weight and ochratoxin production were measured. A delay in mycelial growth of 24 and 48h over the control occurred following irradiation of mycelial discs with 150 and 200 krad, respectively. No growth occurred from discs exposed to 300 krad. An increase in ochratoxin production occurred on the SM from cultures developing from discs of mycelium which had been irradiated with 50, 100, 150 and 200 krad. The amount of toxin produced was 3500, 4100, 3200 and 3000 ng per plate, respectively, as compared with 2800 ng per plate produced by the control. Exposure of mycelial discs to a temperature of 40°C for 15 and 30 min prior to treatment with 200 krad resulted in complete inhibition in mycelial growth. No growth inhibition or notable change in ochratoxin production was recorded when the mycelial discs were exposed to 25, 50 or 100 krad after the heat treatments. Pure ochratoxin was found to be stable even at 7.5 mrad, and no reduction in its fluorescence intensity under u. v. light was recorded following that dose.

Influence of white light, near‐UV irradiation and other environmental conditions on production of aflatoxin B1 by Aspergillus flavus and ochratoxin A by Aspergillus ochraceus

“…The effect of radiation on mycotoxin production was studied mainly concerning aflatoxin [3] and ochratoxin [32]. Aziz [4] revealed that UV-radiation induced synthesis of mycotoxins (aflatoxins and ochratoxin A) by nonNational Center for Radiation Research and Technology, Food Microbiology Department, P.O.…”

Influence of UV radiation and nitrosamines on the induction of mycotoxins synthesis by nontoxigenic moulds isolated from feed samples

“…From this study, it is clear that all metabolities of nontoxigenic fungal strains A. flavus EP-63, A. niger EN-200 and A. ochraceus P-157 which were able to synthesize mycotoxins under the influence of UV radiation decreased greatly the percentage of plant seed germination (5-16%) as compared to control (83-98%). Most of the work dealing with the effect of radiation on fungi has been focused on asexual spores [4,7,18,19,24]. This can be attributed mainly to the importance of the spore as infesting propagules and their common structure as single cell with one nucleus.…”

“…This can be attributed mainly to the importance of the spore as infesting propagules and their common structure as single cell with one nucleus. Several studies [7,11,19] revealed that higher concentrations of aflatoxins were produced by strains of A. flavus and A. parasiticus and ochratoxin A by A. ochraceus in irradiated foods than in unirradiated controls. The role of radiation, especially UV in the mutation of fungal spores is nowadays an interesting research point.…”

“…The effect of radiation on mycotoxin production was studied mainly concerning aflatoxin [4,7,14,18] and ochratoxin [11,19,21]. The lethal effect of ionizing radiation on moulds have been investigated by several workers [4,7,12].…”

Correlation of growth and aflatoxin production by Aspergillus flavus with some essential metals in gamma irradiated crushed corn

“…There are number of conflicting reports which suggest that the production of mycotoxins is either increased [28,34], decreased [35,36,38] or unaffected [27] after irradiation of grains or spores under various laboratory conditions. The present study was designed to evaluate the relationships between the addition of iron, copper or zinc to crushed corn and the growth rate and aflatoxin B 1 production by Aspergillus flavus after different storage periods.…”