Fig.9
Mechanism of ZIF-8/RGO for DAADH immobilization was thought about multi-level interactions include coordination bonds, hydrogen bonds, electrostatic interactions and hydrophobic effect (Fig.10). There will probably be coordination bonds, hydrogen bonds and electrostatic interactions between DAADH and ZIF-8. Controllable immobilization of DAADH within ZIF-8 was crucial for achieving efficient catalysis and high stability. As for DAADH and RGO, it will be hydrophobic effect, which can improve the stability. ZIF-8/RGO is showed to be a good carrier for DAADH and the DAADH/ZIF-8/RGO has potential in biocatalysis
. Fig.10

3.10 One-step separation and immobilization of enzyme by bimetal MOF

One-step separation and immobilization of DAADH from crude enzyme solution by bimetal based MOF was studied. Integrate of separation and immobilization of enzyme directly from cell lysis solution in a single biomineralization step. Bimetal-based MOF was developed to immobilize DAADH by nickel (Ni) and zinc (Zn) ions. ZIF-8/RGO/Ni composite for in situ immobilization of D-amino acid dehydrogenase obtained 1.5-fold activity of free enzyme. Kinetic parameters of DAADH-ZIF-8/RGO/Ni-DAADH were calculated and the results confirmed the enhancement of activity (Table 2).