Department of Environmental Engineering, College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China.
Department of Environmental Engineering, College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China.
Chemosphere. 2023 Jul;330:138654. doi: 10.1016/j.chemosphere.2023.138654. Epub 2023 Apr 10.
Enzymes immobilized on the surface of the carriers are difficult to maintain their conformation and high activity due to the influence of the external harsh environments. A biomimetic core-shell PDA@Lac bioreactor was constructed by depositing polydopamine (PDA) on the surface of the recombinant Escherichia coli with CotA laccase gene, and releasing intracellular laccase into the PDA shell using ultrasound to break the cell wall of the bacteria. The bioreactor provided a nano-confined environment for the laccase and accelerated the mass and electron transfer in the volume-confined space, with a 2.77-fold increase in Km compared with the free laccase. Since there was no barrier of the cell wall, the crystal violet dye can enter the bioreactor to participate in the enzymatic reaction. As a result, PDA@Lac achieved excellent decolorization performance even without ABTS as an electron mediator. Moreover, the cytoplasmic solution retained in the PDA shell promoted the enzyme's tolerance to pH, temperature and harsh environments. In addition to PDA encapsulation, carbonyl and -NH groups of PDA were bound covalently with -NH and -COOH on the laccase in the PDA@Lac, resulting in an extremely high laccase loading of 817.59 mg/g. Also, the relative activity of the bioreactor maintained approximately 75% after 10 cycles of reuse. In addition, the protection of the PDA shell increased the resistance of laccase to UV irradiation. This work provides a novel method of laccase immobilization for application in wastewater treatment.
由于外部恶劣环境的影响，固定在载体表面的酶很难保持其构象和高活性。通过在携带 CotA 漆酶基因的重组大肠杆菌表面沉积聚多巴胺（PDA），并利用超声打破细菌细胞壁将细胞内漆酶释放到 PDA 壳中，构建了仿生核壳 PDA@Lac 生物反应器。该生物反应器为漆酶提供了纳米限域环境，并加速了体积限域空间中的质量和电子转移，与游离漆酶相比，Km 增加了 2.77 倍。由于没有细胞壁的障碍，结晶紫染料可以进入生物反应器参与酶促反应。结果，PDA@Lac 即使没有 ABTS 作为电子介体也能表现出优异的脱色性能。此外，保留在 PDA 壳中的细胞质溶液促进了酶对 pH 值、温度和恶劣环境的耐受性。除了 PDA 封装外，PDA 的羰基和-NH 基团与 PDA@Lac 中的漆酶上的-NH 和-COOH 发生共价结合，导致漆酶的负载量极高，达到 817.59 mg/g。此外，该生物反应器在重复使用 10 次后，相对活性保持在约 75%。此外，PDA 壳的保护增加了漆酶对紫外线照射的抵抗力。这项工作为漆酶在废水处理中的应用提供了一种新的固定化方法。
