Production of Aflatoxin by Aspergillus flavus from Different Edible Foodstuffs of Kathmandu

  • R. Acharya National College, National Institute of Science and Technology,Lainchour; Kathmandu
  • M. P. Baral Royal Nepal Academy of Science and Technology, GPO Box 3323, Kathmandu
  • R. P. Adhikari Central Department of Microbiology, Tribhuvan University, Kirtipur; Kathmandu
  • I. B. Joshi Nepal Bureau of Standards and Metrology, Balaju, Kathmandu


Aflatoxins are secondary metabolites produced by Aspergillusflavus and A. parasiticus. These molds are quite ubiquitous and frequently contaminate most of the agricultural commodities. Corn and peanuts are the most sensitive commodities to aflatoxin contamination. Animal products such as milk and milk products may contain aflatoxin residue due to consumption of toxic feeds by animals. Aflatoxins are potent heptocarcinogens. Among different aflatoxins, aflatoxin B1 is the most potent one. Studies of 30 edible foodstuffs taken from the retail markets of Kathmandu showed that 23.33% samples were contaminated with aflatoxin. Of total samples analysed, about 50% of corn and 20% of peanuts were detected with aflatoxins, exceeding the tolorence limit in all these samples (tolorence limit for food 30ppb according to Protein Advisory Group). But cheese samples were free of aflatoxin contamination. A rapid screening of aflatoxin producing fungi showed that out of 42 isolates, 15 were A. flavus andonly four of them produced aflatoxins. Aflatoxins produced in semisynthetic medium were extracted by solvent extraction procedure using chloroform. Densitometric analysis showed that the amount of aflatoxin B1 producedby an isolate of A. flavus was 16.μg in 20 ml YES broth when incubated at 28+2oC for 15 days and was the most potent aflatoxin producer. Similarly, other isolates produced 14.05 g, 5.16 g and 1.02 g in 20 ml YES broth incubated at 28+2o C.