Enzyme immobilized in BioMOFs: Facile synthesis and improved catalytic performance

Biological metal-organic frameworks (BioMOFs), an emerging sub-class of MOFs, are prepared from metals and biological ligands (bioligands). Benefit from the low toxicity and good biocompatibility of bioligands, BioMOFs can be used in biomedicine and biocatalysis. In this work, a novel approach was developed for fabricating BioMOFs materials (Co-Cys BioMOFs) from cobalt salt and cystine, meanwhile nitrile hydratase (NHase) was in-situ encapsulated during the synthesis process. The obtained NHase-BioMOFs biocomposits named NHase@Co-Cys was characterized by SEM, TEM, XPS, etc. The preparation parameters and stabilities of NHase@Co-Cys were investigated. The maximum encapsulation yield and specific activity of NHase@Co-Cys were 92.71% and 139.04 U/g_{immobilized NHase}, respectively. The thermal stability of NHase@Co-Cys was improved by approximately 5-fold at 55 °C. The activity of NHase after immobilization was retained nearly 60% after incubating at pH 4.0 and 10.0 for 7 h. The NHase@Co-Cys showed similar catalytic capacity compared with free NHase in producing nicotinamide. After 7 h of reaction catalyzed by free NHase (14.51 U) and NHase@Co-Cys (12.76 U), the yield of nicotinamide was 90.94% and 86.36%, respectively. The activity of NHase@Co-Cys remained 83.85% of the original activity after recycling for 10 times. These results suggested that the NHase@Co-Cys is an effective approach to enhance the enzymatic properties and demonstrated a broad application prospect in industrial production.