Abstract:

This work aims to enrich the resources of biodegradable aflatoxin B₁（AFB₁）and to study the extracellular enzymatic properties of degrading AFB₁ by the screened Bacillus subtilis WTX1 as well as its degradation sites. Liquid chromatography tandem triple quadrupole mass spectrometry（UPLC-MS/MS）was used to detect the degradation solution by degrading three compounds with similar structures to the AFB₁ toxicity site. The two main extracellular enzymes degrading AFB₁ were Ea and Eb after chromatographic separation. The optimal degradation conditions: degradation enzyme Ea was in 50℃ and pH 5, and the degradation rate was up to 88.4%; degradation enzyme Eb was in 37℃ and pH 5, the degradation rate was 73.4%. The action sites of Ea enzyme were the double bond of furan ring, vanillin endo-ring and pentenone ring structure of AFB₁. The action sites of Eb enzyme were the vanillin endo-ring and pentenone ring structure of AFB₁. The degradation pathway of the enzyme group was via hydrolysis, hydrogenation and continuous removal of -CO group. In conclusion, the extracellular enzyme of strain WTX1 destroys the AFB₁ virulence sites by hydrolysis and thus plays a degradation role. The enzyme has good thermal stability, wide temperature and pH adaptability, which meet the harsh conditions of industrial processing.

Key words: aflatoxin B₁, Bacillus subtilis, AFB₁ -degrading enzyme group, degradation sites, product analysis