Repression of Aflatoxigenic Traits in Aspergillus flavus SWtS01 Through Random Mutagenesis
Ekundayo Temitope Cyrus
Arotupin Daniel Juwon
2016, 6(1-2), 25-33.
Background and Objective: Aflatoxins production has limited the use of many strains of Aspergillus flavus in food fermentation and enzyme technology, despite their excellent abilities for copious enzyme production. In a bid to overcome this problem, the effects of some selected mutagenic agents on expression of aflatoxigenic traits in A. flavus was investigated in order to enhance its potential biotechnological uses. Materials and Methods: Spores of the strain were treated with chemical mutagens which include nitrous acid, sodium azide, ethyl methane sulphonate and hydroxylamine and ultraviolet radiation for 5400 sec. Mutants obtained at every 900 sec successively were stored under protection away from light for 24 h in order to stabilize DNA dimmers and the mutants were grown in aflatoxin production medium at 30°C for 10 days. Aflatoxins produced were quantified using enzyme-linked immunosorbent assay. Data obtained were subjected to analysis of variance using Statistical Package for Social Science (SPSS) version 17 at p≤0.05. Results: Ultraviolet treatment achieved 93.11% reduction of aflatoxins expression in the mutant CTUV75 (103.31±0.44 ppt) compared to wild strain. However, hydroxylamine showed 89.40% expression of aflatoxigenic traits in the CTNH2OH60 compared to the parent. Conclusion: Ultraviolet radiation caused considerable repression (93.11%) of aflatoxin production in the A. flavus strain in contrast to other mutagens. Nevertheless, the equivalent concentration of aflatoxin produced still exceeded 50 ppt limits set by FAO/WHO/EU. Thus, the use of such mutant in fermentation could pose public health risk. Therefore, it is suggested that further trials of UV treatment or other molecular methods may be employed whether aflatoxins production could be reduced below the standard limit or entirely get rid off in the mutant.
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