Screening and Characterization of a Chryseobacterium timonianum Strain with Aflatoxin B1 Removal Ability.

Introduction: Aflatoxin B1 (AFB1) is a potent hepatocarcinogenic mycotoxin found in animal feed and human food components. AFB1 contamination poses severe food safety and economic consequences.

Methods: In this study, we used a coumarin-selective medium to isolate bacterial strains that can remove AFB1. Among the isolated bacterial strains, strain c4a exhibited the highest AFB1 removal activity. This strain was subjected to biochemical and phylogenetic characterization. The AFB1 removal activity of the extracellular supernatant of this strain was optimized for growth medium, reaction temperature, pH, and metal ions. The degradation products were analyzed using UPLC-ESI MS/MS.

Results: Strain c4a was found to be most closely related to Chryseobacterium timonianum. The extracellular supernatant of C. timonianum c4a grown in a modified nutrient broth (with gelatin peptone and beef extract in a 4:1 ratio) demonstrated the highest AFB1 removal activity when incubated with 1 ppm AFB1 at 60°C, pH 8, and Mn2+ or Mg2+ supplementation for 72 h. Surprisingly, the autoclaved extracellular supernatant also retained AFB1 removal activity. UPLC-ESI MS/MS analysis suggested that AFB1 was transformed into a metabolite (m/z value 285.08) by water molecule addition on furan ring double bond.

Conclusion: The AFB1 removal activity of C. timonianum c4a was extracellular, constitutive, and highly thermostable, structurally transforming AFB1 into a much less toxic product. Herein, we present the first evidence of thermostable AFB1 removal activity of a strain belonging to C. timonianum.