Decomposition of Aflatoxin in Soil1
- J. S. Angle and
- G. H. Wagner2
Corn infected by Aspergillus flavus and A. parasiticus is frequently contaminated with aflatoxin. If the contamination exceeds 20 ppb, the corn is considered unfit for animal consumption and is often plowed into the soil. This study was undertaken to determine the fate of aflatoxin in the soil. Aflatoxin B1 was added to soil at a rate of 10,000 ppb. The soil was periodically extracted with acetone, and the quantity and species of aflatoxins were determined using thin-layer chromatographic procedures. The rate of decomposition was also monitored by adding 14C-aflatoxin to the soil and periodically measuring the evolution of 14CO2.
Aflatoxin B1 was observed to be rapidly reduced to aflatoxin B2 when added to the soil. The speed of this reaction suggests a chemical mechanism. The resulting aflatoxin B2 decomposed at a much slower rate, declining to a level where it could no longer be detected at 77 days. Aflatoxin G2 was also detected 2 days after the addition of aflatoxin B1 to the soil. Its concentration remained, however, well below that of the other aflatoxins observed. Aflatoxin G2 reached a maximum concentration at 14 days after the addition of aflatoxin B1 to the soil and was no longer detectable at 49 days. Microbial decomposition of 14C-aflatoxin B1, as measured by CO2 evolution, accounted for 14% of added 14C in 112 days of incubation. When wheat straw or sugar was added to the soil, the amount of aflatoxin C liberated as CO2 was less.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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