Bioaccumulation and transformation of U(VI) by sporangiospores of Mucor circinelloides

The bioaccumulation and transformation of U(VI) by sporangiospores of Mucor circinelloides under different environmental conditions (e.g., reaction time, pH, carbonate, sporangiospores concentration, and temperature) was investigated by batch, XPS and EXAFS techniques. The bioaccumulation kinetics and isotherms can be fitted by the pseudo-second-order kinetic mode and Langmuir model, respectively, due to the high correlation coefficient. The maximum bioaccumulation capacity of sporangiospores for U(VI) was 166.13 mg/g at pH 6.0, which was significantly higher than that of other mycelia or spores. The intracellular and extracellular morphology of sporangiospores were significantly changed after U(VI) bioaccumulation, and levels of intracellular H2O2, O-3(-), GPx and SOD compounds in sporangiospores increased significantly. XANES analysis confirmed that the intracellular U(VI) was reduced to U(IV) by sporangiospores, and U(IV) might be stably associated with oxygen-bearing functional groups by EXAFS analysis. These results show that the sporangiospores can be used a promising adsorbent for the bioaccumulation and transformation of U(VI) from aqueous solutions, which has important scientific significance for the immobilization of U(VI) in environmental remediation.

采用分批实验、X射线光电子能谱（XPS）和扩展X射线吸收精细结构（EXAFS）技术，研究了在不同环境条件（例如反应时间、pH值、碳酸盐、孢囊孢子浓度和温度）下，卷枝毛霉（Mucor circinelloides）的孢囊孢子对U(VI)的生物累积和转化。由于相关系数较高，生物累积动力学和等温线分别符合准二级动力学模型和朗缪尔模型。在pH值为6.0时，孢囊孢子对U(VI)的最大生物累积量为166.13 mg/g，显著高于其他菌丝体或孢子。U(VI)生物累积后，孢囊孢子的细胞内和细胞外形态发生显著变化，孢囊孢子内的过氧化氢（H₂O₂）、超氧阴离子（O₃⁻）、谷胱甘肽过氧化物酶（GPx）和超氧化物歧化酶（SOD）化合物水平显著升高。X射线吸收近边结构（XANES）分析证实，孢囊孢子将细胞内的U(VI)还原为U(IV)，并且扩展X射线吸收精细结构（EXAFS）分析表明，U(IV)可能与含氧官能团稳定结合。这些结果表明，孢囊孢子可作为一种有前景的吸附剂，用于水溶液中U(VI)的生物累积和转化，这对环境修复中U(VI)的固定具有重要的科学意义。