Bioconversion of Aflatoxin G1 to Aflatoxin B 3 by selected fungi

Aflatoxin G1 (AFG1) was transformed into aflatoxin B3 (AFB3) by the fungiRhodotorula sp,Sporobolomyces sp,Rhizopus oryzae NRRL395,Pythium ultimum, Aspergillus terreus, A clavatus and Penicillium frequentans grown in a medium containing AFG1, Difco potato dextrose broth, yeast extract, and peptone both in liquid shaken cultures and in solid static cultures at 25°C in the dark. A maximum rate of transformation of 10 % was obtained after 2 to 3 weeks of incubation. The transformation was correlated with an increase in the pH of the media from 5.7 -5.9 to 8.3 - 8.8.Saccharomyces cerevisiae also transformed AFG1 into AFB3, but at a slower rate; the pH of the media did not reach above 8.0 until 5 weeks after incubation. No transformation was observed whenA niger andP chrysogenum were tested; in both cases, no increase in pH was noticed. However, some transformation of AFG1 to AFB3 by both fungi was observed when the initial pH of the media was adjusted to 9.0. The rate of transformation increased to 15 - 20% in the static culture where the same medium was adsorbed onto vermiculite andRhizopus andAspergilli gave the highest increase in AFB3 yield.