Biodegradation of Aflatoxin B1 by Neurospora sp.

Aflatoxin B1 (AFB1) is the most common mycotoxin found in foods in tropical countries like Indonesia. Detoxification would be the important strategy step in food processing to reduce or eliminate AFB1 since aflatoxins are relatively resistant to common processing conditions. Microorganisms such as molds (Rhizopus oligosporus, Rhizopus oryzae, Aspergillus oryzae) and becteria (Flavobacterium aurantiacum, Lactobacillus, Propionibacteri) have been reported to degrade aflatoxins. Oncom is an Indonesian fermented food produced from fermentation of peanut press cake by the mold Neurospora sp. It is usual that peanut has high contamination of AFB1, therefore research on the ability of Neurospora sp. to degrade AFB1 is very important in order to minimize its toxic effect.

Direct plating on Dichloran Rose Bengal Cloramphenicol Agar (DRBC) was used for mold isolation. After identification, the isolate was transferred on Potato Dextrose Agar (PDA) slant for working culture. Evaluation of their ability to degrade AFB1 was performed by mold inoculation into Czapek Yeast Extract (CY) broth that was already contaminated by AFB1. The mycelium was disrupted by using sonicator afterwards the concentration of AFB1 in medium and the binding AFB1 in mycelium were analyzed by HPLC-fluorescence detector. Bioassay of degradation product was performed by Bacillus megaterium shape in order to determine their toxicity.

This trial indicates that decreasing AFB1 in the medium was fast during the four days of their growth, correlated with the rate of increasing the biomass during the logarithmic growth phase. The lower growth of the biomass in medium spiked with AFB1 may due to the fact that AFB1 affecting their ability to grow. However, the analyses of dried biomass in medium spiked with AFB1 were relatively lower in the range of 3.7% – 29.3% compared to control. Small amount of AFB1 was bound to the cells after 8 days incubation. Neurospora sp. isolated from oncom was able to degrade and detoxify AFB1. It was indicated by the results of bioassay that Bacillus megaterium was not intoxicated by degradation products. The mechanisms of bioreduction may be due to the binding of AFB1 in the mycelium or/and might be due to the extracellular enzymes and shoud be investigated in future experiments.

Published in : 29th Mycotoxins Workshop, 2007, Germany