Presence of aiiA homologue genes encoding for N-Acyl homoserine lactone-degrading enzyme in aflatoxin B1-decontaminating Bacillus strains with potential use as feed additives

Microbial degradation of aflatoxins (AFs) is an alternative to the use of mycotoxin binders. The lactone ring is a possible target for microbial enzymes and its cleavage reduces AFs toxicity. The aim of this study was to isolate and identify Bacillus strains able to degrade AFB(1) to less toxic metabolites and to identify aiiA genes encoding for N-acyl-homoserine lactone (AHL) lactonase to possibly correlate detoxification with the production of this enzyme. Eleven soilborne Bacillus strains were isolated and identified by MALDI-TOF MS. Ten cultures and eight cell free culture supernatants (CFCS) were able to significantly (P < 0.05) degrade 27.78-79.78% AFB(1). Cell lysates were also able to degrade AFB(1) (P < 0.05). Exposure to 70 and 80 degrees C did not affect enzyme activity. Aflatoxin B-1 toxicity towards Anemia salina was reduced after degradation by each of the Bacillus strains. B. subtilis RC1B, B. cereus RC1C and B. mojavensis RC3B, amplified a fragment of 753 pb corresponding to the ciiA gene encoding for AHL lactonase. AFB(1) degradation by the strains tested was due to the extracellular and intracellular enzymes. If demonstrated to be safe, these could be used to detoxify AFB(1) in contaminated food or feed.