Influence of competitive microbial flora and inoculum size of Penicillium purpurogenum on the production of rubratoxin-B in corn medium before and after exposure to gamma radiation |
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Authors: | Soad S Abd El-Aal N H Aziz |
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Affiliation: | National Centre for Radiation Research and Technology, P. O. Box 29, Nasr City, Cairo, Egypt |
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Abstract: | The influence of inoculum size on the production of rubratoxin-B by P. purpurogenum was estimated on unirradiated and irradiated corn stored for prolonged periods at 28 °C and at a moisture content of 25%. Irradiation at doses of 1.0–3.0 kGy reduced the level of mould growth greatly relative to unirradiated controls. Rubratoxin-B production in corn grains at all doses after 40 days was less than the unirradiated control level and was below the detection limit above 4.0 kGy. Non-sterile corn that was inoculated with conidia of the fungus and then irradiated with 2.0 kGy gamma rays, produced lower rubratoxin-B levels compared with unirradiated controls. When corn was inoculated with 105 spores per gram after irradiation, the spore count and rubratoxin-B level were higher than the unirradiated control after 60 days. The total viable counts of endogenous fungal flora in the corn were reduced by the 2-kGy radiation dose, but after 20 days of incubation the numbers of P. purpurogenum increased with greater enhancement of rubratoxin-B production. |
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Keywords: | P purpurogenum rubratoxin-B gamma-radiation |
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