One-Step Purification and Immobilization of Glycosyltransferase with Zn-Ni MOF for the Synthesis of Rare Ginsenoside Rh2.

Uridine diphosphate (UDP)-glucosyltransferases (UGTs) have received increasing attention in the field of ginsenoside Rh2 conversion. By harnessing the metal chelation between transition metal ions and imidazole groups present on His-tagged enzymes, a specific immobilization of the enzyme within metal-organic frameworks (MOFs) is achieved. This innovative approach not only enhances the stability and reusability of the enzyme but also enables one-step purification and immobilization. Consequently, the need for purifying crude enzyme solutions is effectively circumvented, resulting in significant cost savings during experimentation. The use of immobilized enzymes in catalytic reactions has shown great potential for achieving higher conversion rates of ginsenoside Rh2. In this study, highly stable mesoporous Zn-Ni MOF materials were synthesized at 150 °C by a solvothermal method. The UGT immobilized on the Zn-Ni MOF (referred to as UGT@Zn-Ni MOF) exhibited superior pH adaptability and thermal stability, retaining approximately 76% of its initial activity even after undergoing 7 cycles. Furthermore, the relative activity of the immobilized enzyme remained at an impressive 80.22% even after 45 days of storage. The strong specific adsorption property of Zn-Ni MOF on His-tagged UGT was confirmed through analysis using polyacrylamide gel electrophoresis. UGT@Zn-Ni MOF was used to catalyze the conversion reaction, and the concentration of rare ginsenoside Rh2 was generated at 3.15 µg/mL. The results showed that Zn-Ni MOF is a material that can efficiently purify and immobilize His-tagged enzyme in one step and has great potential for industrial applications in enzyme purification and ginsenoside synthesis.

Immobilization of Laccase by Alkali-Etched Bimetallic CoCu-MOF To Enhance Enzyme Loading and Congo Red Degradation.

In this work, the strategy of immobilizing enzymes in bimetallic-organic frameworks was adopted to overcome the disadvantages of free laccases. The surface amino-silanizing of bimetallic CoCu-MOF-H hydrothermally synthesized was performed by (3-Aminopropyl)triethoxysilane (APTES). Then, glutaraldehyde was used as the cross-linking agent, laccase was covalently grafted onto CoCu-MOF-H-APTES to prepare Lac-CoCu-MOF-H-APTE. In addition, CoCu-MOF-OH also was synthesized by alkali etching of CoCu-MOF-H, and Lac-CoCu-MOF-OH-APTES composites were obtained by a similar strategy. The result showed that the relative enzyme activity of Lac-CoCu-MOF-OH-APTES exhibited 264.02% (1.8 times than that of Lac-CoCu-MOF-H-APTES) after six cycles of stability tests, while the free enzyme was almost inactivated. Moreover, the Congo red (CR) removal rate of Lac-CoCu-MOF-OH-APTES exceeded 95% within 1 h and exceeded 89.18% after six cycles at pH 3.5 and 50 °C. This work has the potential to provide a broader application prospect for CR degradation by laccase in the future.