Now, Insung S. Choi and colleagues report a biocompatible method for generating enzyme-containing metal hydroxide HISs (MH-HISs). The researchers mixed CaCO3 microspheres — preloaded with enzymes — and metal salts in deionized water at room temperature and mild pH, triggering a topological evolution of the CaCO3 particles into the desired MH-HISs (pictured). To explore the compatibility with enzyme cascades the researchers produced Fe-HIS[GOx/HRP] with glucose oxidase (GOx) and horseradish peroxidase (HRP) in the shells of the carrier. The biocatalytic reactor was tested in a model reaction, whereby D-glucose is oxidized by GOx yielding D-gluconic acid and hydrogen peroxide that is used by HRP to oxidize 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS). The cascade reaction of Fe-HIS[GOx/HRP] exhibited significantly faster rates compared to CaCO3[GOx/HRP] and CaCO3/Fe[GOx/HRP], which appear as intermediate structures in the course of the described synthetic protocol. After the reaction, Fe-HIS[GOx/HRP] could be recovered through centrifugation and over 90% of the enzymatic activity was retained after four recycling steps with no morphological changes of the carrier. Further, the researchers also showed that MH-HISs can protect the enzymes from degradation by proteases. The improved catalytic efficiency was also observed for the three-enzyme cascade consisting of α-amylase, GOx, and HRP, whereby an additional step is introduced, namely the hydrolysis of maltodextrin to release D-glucose for the subsequent reactions with GOx and HRP as described above.
The large voids and porous shells make the MH-HISs appealing carriers for catalysis. Since the synthetic protocol developed by Insung S. Choi and colleagues for their construction is rapid, mild, and easy to implement, there are good chances that they will be more widely applied in biocatalysis and other biological fields such as biomedicine in the future.
This is a preview of subscription content, access via your institution
