Inhibiting <i>Aspergillus flavus</i> growth and degrading aflatoxin B1 by combined beneficial microbes

Abstract

Aflatoxin B₁ (AFB₁) is a type of toxin produced by Aspergillus flavus, which has a negative effect on animal production and economic profits. In order to inhibit A. flavus growth and degrade aflatoxin, the optimal  proportion of beneficial microbes such as Lactobacillus casei, Bacillus subtilis and Pichia anomala were selected. The results show that AFB₁ production and mycelium weight of A. flavus was decreased by more than 34 folds (161.05 vs. 4.69 µ/L) and 7.7 folds (6.98 vs. 0.90 mg/ml) with the free-cell supernatants of L. casei and B. subtilis (P<0.05), respectively. The optimal proportion of L. casei, B. subtilis and P. anomala was 2:1:2 for inhibiting A. flavus growth determined by 3x3 orthogonal design. Based on the optimal proportion of three microbial species, the maximum AFB1 degradation was during 24 to 48 h incubation (P<0.05). When three species of beneficial microbes were mixed with yeast cell wall and oligosaccharide, both of them could not help the microbes in AFB1 degradation. The combined microbial incubation showed that AFB1 contents in the supernatant and cells were 10.25 (P<0.05) and 3.34 µg/L, lower than the control group (68.55 µg/L), indicating that most of the AFB₁ were degraded by the microbes and only a little of them were absorbed and deposited in microbial cells.

Key words: Aspergillus flavus, aflatoxin B₁ detoxification, beneficial microbes, yeast cell wall, oligosaccharide.