Microbial Degradation of Aflatoxin in Maize : A Biocontroi Approach for Management of Preharvest Aflatoxin Contamination

摘要

Four filamentous fungi Aspergillus niger, Alternaria alternata, Mucor racemosus and Rhizopus oryzae and one bacterium Bacillus subtilis were isolated from rhizosphere soil of standing maize crop at Bhagalpur, Bihar. Toxigenic Aspergillus flavus aloneor in association with each of these microorganisms was inoculated onto irradiation-sterilized maize seeds and incubated aseptically in microporous bags at 30C and 0.95 a_w and analyzed for total aflatoxins at 5 and 10 days. After 5 days, all combinations yielded less total aflatoxins than the single culture of A. flavus. Continued cultivation for 10 days resulted in an approximately 20% decrease in aflatoxin levels in only A. flavus inoculated control. Similar decreases of 28, 30 and 32% with R. oryzae, A. niger and B. subtilis, respectively were observed. Incubation at 40C after an initial 5 days incubation at 30C gave increased degradation of aflatoxin by A. flavus (40%) with similar results with dual cultutres with M. racemosus and A. alternata. However, dual combination with A. niger, R. oryzae and B. subtilis resulted in 82, 80 and 83% degradation of total aflatoxins, respectively.