Harmful Microcystis blooms and microcystins have become a major hidden threat to the safety of the water environment. The application of enzymatic degradation of microcystins has been severely limited by the complex environment. In this study, chitosan-graphene (CG), prepared from green biomass, was employed as matrix material, loaded with 100–200 nm Fe3O4 nanoparticles (MCG) and immobilized microcystinase A (MlrA@MCG). The preparation of MlrA@MCG was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and fluorescence labelling. The results of the activity analysis demonstrated that MlrA@MCG exhibited superior degradation activity for MCs, as well as enhanced heat and alkaline resistance in comparison to free MlrA. Furthermore, MlrA@MCG can be recovered simply by means of a magnetic field, and its activity remains at 48.6 % after 10 repeated uses. More importantly, MlrA@MCG and the degradation products of MC-LR were not found to be cytotoxic to human cells. It is interesting that the immobilization of MlrA resulted in a reduction in the cytotoxicity of MCG. 0.2 U of MlrA@MCG can still degrade MC-LR from 232.64 μg L−1 to 94.39 μg L−1 in water from simulated severe Microcystis blooms within 24 h, showing excellent catalytic activity and stability. The study proposed a secure and efficacious approach for the elimination of microcystins from harmful Microcystis blooms, offering a promising avenue for the improvement of environmental safety.

中文翻译：

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磁性可回收壳聚糖-石墨烯固定化微囊藻酶 A：从有害的微囊藻藻华中去除微囊藻毒素


有害的微囊藻藻华和微囊藻毒素已成为对水环境安全的重大隐患。微囊藻毒素酶促降解的应用受到复杂环境的严重限制。在这项研究中，由绿色生物质制备的壳聚糖-石墨烯 （CG） 作为基质材料，负载 100-200 nm Fe3O4 纳米颗粒 （MCG） 和固定化微囊藻氨酸酶 A （MlrA@MCG）。采用扫描电子显微镜、傅里叶变换红外光谱、X 射线衍射、振动样品磁强计和荧光标记对 MlrA@MCG 的制备进行了表征。活性分析结果表明，与游离 MlrA 相比，MlrA@MCG对 MCs 表现出优异的降解活性，并且具有更强的耐热性和耐碱性。此外，MlrA@MCG 可以简单地通过磁场进行回收，并且在重复使用 10 次后，其活性仍保持在 48.6%。更重要的是，未发现 MlrA@MCG 和 MC-LR 的降解产物对人体细胞具有细胞毒性。有趣的是，MlrA 的固定导致 MCG 的细胞毒性降低。0.2 U MlrA@MCG 仍可在 24 小时内将模拟严重微囊藻水华的水中 MC-LR 从 232.64 μg L-1 降解到 94.39 μg L-1，显示出优异的催化活性和稳定性。该研究提出了一种安全有效的方法来消除有害微囊藻毒素水华中的微囊藻毒素，为改善环境安全提供了一条有前途的途径。