Immobilization of purified enzyme EreB in metalorganic framework (MOF) mesopores for erythromycin degradation

Erythromycin, a commonly used macrolide antibiotic, plays a crucial role in both human medicine and animal husbandry. However, its abuse has led to residual presence in the environment, with problems such as the emergence of resistant bacteria and enrichment of resistance genes. These issues pose significant risks to human health. Thus far, there are no effective, environmentally friendly methods to manage this problem. Enzymes can specifically degrade erythromycin without causing other problems, but their unrecyclability and environmental vulnerability hinder large-scale application. Enzyme immobilization may help to solve these problems. This study used Cu-BTC, a synthetic metal-organic framework, to immobilize the erythromycin-degrading enzyme EreB. The loading temperature and enzyme quantity were optimized. The Cu-BTC and EreB@Cu-BTC were characterized by various methods to confirm the preparation of Cu-BTC and immobilization of EreB. The maximum enzyme loading capacity was 66.5 mg g-1. In terms of enzymatic properties, immobilized EreB had improved heat (25-45 °C) and alkaline (6.5-10) tolerance, along with greater affinity between the enzyme and its substrate; Km decreased from 438.49 to 372.30 mM. Recycling was also achieved; after 10 cycles, 57.12% of the enzyme activity was maintained. After composite degradation, the antibacterial activity of erythromycin-containing wastewater was examined; the results showed that the novel composite could completely inactivate erythromycin. In summary, Cu-BTC was an ideal carrier for immobilization of the enzyme EreB, and the EreB@Cu-BTC composite has good prospects for the treatment of erythromycin-containing wastewater.

Immobilization of EreB on Acid-Modified Palygorskite for Highly Efficient Degradation of Erythromycin

Erythromycin is one of the most commonly used macrolide antibiotics. However, its pollution of the ecosystem is a significant risk to human health worldwide. Currently, there are no effective and environmentally friendly methods to resolve this issue. Although erythromycin esterase B (EreB) specifically degrades erythromycin, its non-recyclability and fragility limit the large-scale application of this enzyme. In this work, palygorskite was selected as a carrier for enzyme immobilization. The enzyme was attached to palygorskite via a crosslinking reaction to construct an effective erythromycin-degradation material (i.e., EreB@modified palygorskite), which was characterized using FT-IR, SEM, XRD, and Brunauer-Emmett-Teller techniques. The results suggested the successful modification of the material and the loading of the enzyme. The immobilized enzyme had a higher stability over varying temperatures (25-65 °C) and pH values (6.5-10.0) than the free enzyme, and the maximum rate of reaction (V_max) and the turnover number (k_cat) of the enzyme increased to 0.01 mM min^-1 and 169 min^-1, respectively, according to the enzyme-kinetics measurements. The EreB@modified palygorskite maintained about 45% of its activity after 10 cycles, and degraded erythromycin in polluted water to 20 mg L^-1 within 300 min. These results indicate that EreB could serve as an effective immobilizing carrier for erythromycin degradation at the industrial scale.