Metal-Organic Framework Hybrid Materials of ZIF-8/RGO for Immobilization
of D–amino Acid Dehydrogenase
Abstract
Immobilization of D-amino acid dehydrogenase (DAADH) by the assembly of
peptide linker was studied for biosynthesis of D-phenylalanine which is
an unnatural amino acid. Hybrid material of ZIF-8 and reduced graphene
oxide (RGO) were applied for the immobilization of DAADH from
Ureibacillus thermosphaericus. Activity of DAADH/ZIF-8/RGO was enhanced
by 1.65 folds than free enzyme. DAADH/ZIF-8/RGO remained 53.4% of its
initial activity at 50 °C for 10 h. At the same time the free enzyme was
inactivated. The result indicated that the immobilization greatly
improved the thermostability of DAADH and the stability in hyperalkaline
solution. Kinetic parameters indicated that DAADH/ZIF-8/RGO had greater
affinity of phenylpyruvate as Vm /Km of DAADH/ZIF-8/RGO was 1.27-fold
than free enzyme. After seven recycles, the activity of DAADH/ZIF-8/RGO
remained 64.3%. Furthermore, one step separation and immobilization by
ZIF-8/RGO/Ni-DAADH had 1.5-fold activity enhancement. Combination of
peptide linker and MOF immobilization, thermostability of the
dehydrogenase was significantly improved.