Stabilization of interface-binding chloroperoxidase for interfacial biotransformation

The stability of an interface-binding chloroperoxidase (CPO) against the deactivation effect of H2O2 was examined. Native CPO was conjugated with polystyrene and thus self-assembled at the water–oil interface. Although the interface-assembled CPO showed improved stability as compared to native CPO, enzyme deactivation as a result of the side effect of H2O2, still limits the overall productivity of the enzyme. Two approaches to further improve the stability of CPO were examined in this work. In one approach, several stabilizers including poly(ethylene glycol) (PEG), PEI, glycerol, sugars and sucrose monododecanoate were used; while in a second approach, in situ generation of hydrogen peroxide (H2O2) by using glucose oxidase (GOx) was applied. PEG was found exceptional in that it increased both the operational and storage stability of CPO. The best improvement of enzyme productivity was obtained with addition of PEG which led to an increase of 57% for interface-bound CPO and 33% for native CPO. One interesting observation with PEI is that it enhanced the storage stability against H2O2 deactivation, but did not affect the enzyme's operational stability. On the other hand, glucose enhanced the operational stability by two folds, but exhibited no significant effect on storage stability. It was also found that the extended operational lifetime of CPO with in situ generation of H2O2 by GOx was a result that combines the stabilizing effect of glucose and lowered concentration of H2O2. Interestingly, the addition of stabilizers could improve the enantioselectivity of CPO by as much as 10%.