Abstract: [Objective] To screen superior strains with the ability to inhibit the growth of toxigenic Aspergillus flavus and degrade aflatoxin B1 （AFB₁） from lactic acid bacteria isolated from the digestive tract of dairy goats. [Methods] With 30 strains of lactic acid bacteria from digestive tract of dairy goats as materials, the inhibition rate of cell-free fermentation supernatant （CFS） on spore germination of A. flavus was determined using 96-well plate method, and the degradation rate of AFB₁ by CFS was detected using ELISA method. Superior strains were screened based on the combined results of inhibition rate and degradation rate. The CFS and the antifungal activities of culture broth of the screened strains were evaluated using the agar diffusion method and double-layer plate method, respectively. The composition and changes of organic acids in CFS were analyzed using LC-MS. The effect of culture broth on the morphology of A. flavus was observed by scanning electron microscope （SEM）, and the removal effect of active and inactivated CFS and bacterial culture broth on AFB₁ was compared. [Results] Two superior strains were obtained: Lactobacillus plantarum R3 and Pediococcus pentosaceus I3. The inhibition rates of CFS against A. flavus spores of R3 and I3 strains were higher than 84 %, and the degradation rates of AFB₁ were 81.42% and 81.96%, respectively. The results of agar diffusion method showed that the antifungal activity of CFS of I3 was slightly stronger than that of R3. However, the results of double-layer plate method showed that the antifungal activity of the culture broth of R3 strain was stronger than that of I3 strain. Organic acid analysis showed that lactic acid and pyruvic acid were the main components of CFS, and the pyruvic acid content in the toxin group treated with R3 CFS after interaction with AFB₁ significantly decreased （P<0.05） compared with the R3 control group; after interaction with AFB₁, the DL-3-phenyllactic acid content in the toxin group treated with I3 CFS significantly decreased （P<0.05） compared with the I3 control group. The results of SEM observation showed that the culture broth of both strains resulted in the morphological deformation of A. flavus mycelium and the decrease of spore production. The AFB₁ removal experiment showed that after boiling water inactivation, the total removal rates of R3 and I3 strains increased to 54.36% and 51.65%, respectively. After being inactivated by boiling water, the degradation rate of AFB₁ by CFS of the two strains decreased. The total removal effect of R3 strain on AFB₁ was slightly better than that of I3. [Conclusion] In this study, lactic acid bacteria strains R3 and I3 were isolated from the digestive tract of dairy goats. Both of them can inhibit the growth of A. flavus and remove AFB₁ by producing organic acids. Among them, L. plantarum R3 exhibits stronger antifungal effect and ability to remove AFB₁.

Key words: lactic acid bacteria from digestive tract of dairy goats, Aspergillus flavus, aflatoxin B₁, organic acids