Aflatoxin degradation by Bacillus subtilis UTB1 is based on production of an oxidoreductase involved in bacilysin biosynthesis

Abstract Aflatoxins produced by some strains of the fungal genus Aspergillus are among the most hazardous mycotoxins for humans and livestock, a reason that has forced to investigate efficient strategies of management of these fungal contaminations. Some bacterial species have been proven capable of degrading or modifying aflatoxin into less- or nontoxic derivatives. In a previous work, Bacillus subtilis UTB1 was already proposed as a good candidate to be used for degradation of aflatoxin. Aiming to deepen in this biological activity, in this study, we searched for homologous to enzymes of Mycobacterium smegmatis degrading aflatoxin within the genus Bacillus. A candidate was the gene bacC, an oxidoreductase enzyme dedicated to the production of the antimicrobial di-peptide bacilysin. bacC mutants were compromised in the inhibitory activity against A. flavus, and the degradation of aflatoxin, compared to wild type both in vitro and on pistachio fruits. Taken together, our findings led us to propose a double and complementary mechanism by which BacC contributes to the reduction of aflatoxin levels in pistachio fruits: first, by a direct antagonism towards A. flavus, presumably mediated by the peptide bacilysin, and second, by a degradative or modifying activity of aflatoxin.