Evaluation of Process Parameters Influencing Aflatoxin B1 Synthesis from Aspergillus flavus MTCC 2798 using Rice Straw under Submerged Fermentation

Aflatoxin is a toxic secondary metabolite produced by different species of Aspergillus in food crops when stored under hot and humid conditions. Among the various aflatoxins produced by fungi aflatoxin B1 has been proved to have carcinogenic, mutagenic, teratogenic and immunosuppressive effects. They often contaminate human food, animal feed and agricultural produce. Rice straw acts as a commonly used cattle feed in India. Feeding of moldy straw may lead to aflatoxicosis in cattle and pose serious threat to dairy industry. The present study focuses on the evaluation of various nutritional and physical parameters that influence the synthesis of aflatoxin B1 from Aspergillus flavus MTCC 2798 in rice straw under submerged fermentation. The aflatoxin B1 production was detected by thin layer chromatography and its level was quantified by highperformance liquid chromatography. Among the various semisynthetic media studied yeast extract sucrose medium supported the highest aflatoxin production (55.15 μg/ml). Static or stationary condition yielded higher level of aflatoxin than shaking condition. Among the nutritional parameters, 2% (w/v) rice straw and 0.5% (w/v) peptone supported maximum production of aflatoxin. The highest level of aflatoxin B1 was synthesized at pH 3.5 and at 30°C. An inoculum size of 5% (v/v) resulted in significant toxin production after 30 days of incubation under aerobic condition. It may be concluded that rice straw has the potential to support good production of aflatoxin when incubated under ambient conditions. Therefore, proper storage and periodical monitoring of its quality should be practised to prevent aflatoxicosis in cattle.