Institute of Biotechnology, National Taiwan University, Taipei, Taiwan.
Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan.
Microb Physiol. 2024;34(1):182-196. doi: 10.1159/000540803. Epub 2024 Aug 13.
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.
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.
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.
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.
黄曲霉毒素 B1（AFB1）是一种存在于动物饲料和人类食物成分中的强效肝致癌真菌毒素。AFB1 污染对食品安全和经济造成严重后果。
在这项研究中，我们使用香豆素选择性培养基来分离可以去除 AFB1 的细菌菌株。在所分离的细菌菌株中，菌株 c4a 表现出最高的 AFB1 去除活性。该菌株进行了生化和系统发育特征分析。优化了该菌株胞外上清液在生长培养基、反应温度、pH 和金属离子方面的 AFB1 去除活性。使用 UPLC-ESI MS/MS 分析降解产物。
菌株 c4a 与鞘氨醇单胞菌属（Chryseobacterium timonianum）最为密切相关。在改良营养肉汤（明胶蛋白胨和牛肉提取物的比例为 4:1）中培养的 C. timonianum c4a 的胞外上清液在 60°C、pH8 和补充 Mn2+或 Mg2+的条件下，用 1ppm AFB1 孵育 72 小时时，表现出最高的 AFB1 去除活性。令人惊讶的是，经高压灭菌的胞外上清液也保留了 AFB1 去除活性。UPLC-ESI MS/MS 分析表明，AFB1 通过呋喃环双键上水分子的加成转化为一种代谢物（m/z 值为 285.08）。
C. timonianum c4a 的 AFB1 去除活性是胞外的、组成型的和高度热稳定的，可将 AFB1 转化为毒性较低的产物。本文首次报道了属于鞘氨醇单胞菌属的菌株具有耐热的 AFB1 去除活性。
