Specific Ion Effects on the Enzymatic Degradation of Polyester Films

Soil environment on earth contains a variety of ions, which are expected to play a vital role in the biodegradation of plastics discarded in the environment. In this work, poly(butyleneadipate- co -terephthalate) (PBAT) is employed as a model biodegradable plastic to study the specific ion effects on the enzymatic degradation of polyester plastics. The results show that the specific ion effects on the enzymatic degradation rate of the PBAT films and on the catalytic rate constant for the enzymatic hydrolysis of the ester bonds are strongly dependent on temperature and ionic strength. Both the enzymatic degradation rate and catalytic rate constant decrease following the trends Na + > K + > Ca 2+ and Cl − > SO 4 2− > NO 3 − for cations and anions, respectively, indicating that the ion-specific enzymatic degradation of the PBAT films is closely correlated with the specific ion effects on enzymatic hydrolysis of the ester bonds. Our study shows that the specific ion effects on the enzyme activity can be understood by taking into account the ion-specific cation-anion interaction, ionic dispersion force, salting-out effect and salting-in effect. This study of specific ion effects on the enzymatic hydrolysis of the ester bonds and the resultant enzymatic degradation of the PBAT films would offer us a new clue to develop new biodegradable, environmentally friendly synthetic plastics.