Use of lactic acid bacteria for the inhibition of Aspergillus flavus and Aspergillus carbonarius growth and mycotoxin production

Almonds and peanuts are a rich source of proteins, vitamins and unsaturated fatty acids. However, they can be also contaminated by mycotoxigenic fungi; a reason that has enhanced to investigate efficient strategies of management of these fungal contaminations. Some Lactic acid bacteria have been proven capable of inhibiting growth and mycotoxin production in livestock and transform it into nontoxic derivatives. In this work, four lactic acid bacteria (LAB) were tested for their abilities to inhibit the growth and mycotoxin production of Aspergillus flavus and Aspergillus carbonarius. Antifungal activity was evaluated in agar medium as well as in almonds and peanuts. Results showed that LAB significantly inhibited Aspergillus flavus and Aspergillus carbonarius in agar medium but none of the strains were able to completely inhibit fungal growth. The highest fungal growth inhibition was obtained using L. kefiri FR7 (51.67% and 45.56% growth inhibition of A. flavus and A. carbonarius, respectively). The cell-free supernatants (CFS) from LAB reduced fungal growth with average growth inhibitions ranging from 13.33% to 40.56% and 12.78% to 37.78% for A. flavus and A. carbonarius, respectively. We noted also that cell-free supernatants at pH7 (CFS-pH7) from the entire tested LAB did not inhibit fungal growth. L. kefiri FR7 was the most effective strain in mycotoxin suppression with a reduction percentage reaching 97.22%, 95.27% and 75.26% for AFB1, AFB2 and OTA respectively. Moreover, the inoculation of L. kefiri FR7 in almonds artificially contaminated with A. flavus decrease 85.27% of AFB1 and 83.94% of AFB2 content after 7 days of incubation. On the other hand, application of L. kefiri FR7 in peanuts artificially contaminated with A. carbonarius reduced OTA content to 25%. Our study revealed the potential use and application of L. kefiri FR7 in the control of fungi growth and mycotoxins production in almonds and peanuts.