Biodegradation of aflatoxin B1 by Bacillus subtilis YGT1 isolated from yoghurt

Aflatoxin contamination of food products is recognised as a major food safety concern throughout the world because of its carcinogenic, mutagenic, and immunosuppressive effects on human health. Of the various types of aflatoxins, aflatoxin B1 (AFB1) is the ubiquitous and most threatening foodborne mycotoxin to humans. A wide range of detoxification methods is used to reduce the toxic effects of AFB1. In the present work, the ability of probiotics isolated from yoghurt (produced by bacterial fermentation of milk), "laban" (fermented milk beverage), and "idli" batter (fermented rice and black gram) in the detoxification of AFB1 was investigated under laboratory conditions. Among the four isolates from fermented foods evaluated, the isolate YGT1 from yoghurt showed the maximum (83.8%) degradation of AFB1 in Luria-Bertani (LB) liquid medium after 48 h of incubation at 30 degrees C. The degradation of AFB1 by the probiotic isolate was further confirmed by liquid chromatography/mass spectrometry analysis. On the basis of 16S rRNA gene sequence analysis, the bacterial isolate YGT1 was identified as Bacillus subtilis. The culture supernatant and heat-treated culture supernatant (boiled for 30 min) of B. subtilis YGT1 also exhibited degradation of AFB1, thus suggesting the involvement of thermostable bioactive compound(s) in the degradation of AFB1. These results suggested that B. subtilis YGT1 isolated from yoghurt may be a promising candidate for exploitation in food and feed industries for the removal of AFB1.