BIOLOGICAL DETOXIFICATION OF ZEARALENONE BY BACILLUS SUBTILIS STRAINS

Zearalenone (ZEA) is a non-steroidal estrogen produced by many Fusarium species in cereals and other plants, and is frequently implicated in adverse health effects and economic losses in livestock production. The aim of the present study was to investigate the efficacy of Bacillus subtilis strains in reducing ZEA and its major metabolites of phase I (?-ZAL, ?-ZOL, ?-ZAL, ?-ZOL, ZAL) in culture media. Batch decontamination experiments were performed using different growth media, temperature, pH, incubation time, toxin concentration, and oxygenation. Desorption/extraction experiments and heat/acid treatment of bacteria were carried out to study the mechanism underlying mycotoxins reduction. Mycotoxin content in culture media and cell pellets was determined by UHPLC-FLD/PDA methods after sample purification with immunoaffinity columns. All tested strains were effective in reducing ZEA and its major metabolites in aerobic and anaerobic conditions, and in growth medium containing the toxin as sole carbon source. Reduction of ZEA and metabolites was >90% in mostly tested conditions. Maximum reduction was obtained in less than 24h. Optimal temperature and pH for toxin reduction were 30°C and pH range at 5-8. Desorption/extraction trials suggested that ZEA removal occurred by a metabolism of the toxin involving enzymatic activities, the latter being deactivated in acid- or heat-treated cells. These activities are intracellular and are not released into the growth medium. Indeed, bacterial cultures and viable cell pellets showed significantly higher ZEA removal efficiencies than supernatants. In conclusion, due to its potential to effectively remove ZEA, B. subtilis could be exploited in food and feed chains to reduce mycotoxin contamination. Further studies will be addressed to identify ZEA metabolites produced by B. subtilis strains during the removal of the toxin and relevant toxicity.