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

Abstract

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 AFB₁ 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% AFB₁. Cell lysates were also able to degrade AFB₁ (P < 0.05). Exposure to 70 and 80 °C did not affect enzyme activity. Aflatoxin B₁ toxicity towards Artemia 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 aiiA gene encoding for AHL lactonase. AFB₁ degradation by the strains tested was due to the extracellular and intracellular enzymes. If demonstrated to be safe, these could be used to detoxify AFB₁ in contaminated food or feed.

Keywords: AHL lactonase; Aflatoxin B(1); Bacillus; Degradation; Enzymes.