Selective Hydrolysis by Engineered Cutinases: Characterization of aliphatic-aromatic polyester homo and co-polymers by LC and LC-MS methods

The performance, biodegradability, and recyclability of polymers can be tuned during synthesis by adopting monomers with different chemical characteristics. Recent research has shown the aptness of some hydrolases to depolymerize polyesters under mild conditions compared to chemical approaches. Herein, we engineered a cutinase from Thermobifida cellulosilytica (Tc_Cut2NVWCCG) for improved thermostability (up to 91 °C) and compared it with previously reported leaf-branch compost cutinase (LCCWCCG) for the hydrolysis of low molar mass substrates, aliphatic and aromatic polyester homopolymers, and a co-polyester. For both enzymes, higher hydrolysis rates were observed for aliphatic compared to aromatic homopolyesters. SEC-MS analysis revealed that the hydrolysis of aliphatic/aromatic co-polyesters occurred at the aliphatic monomers, significantly reducing the molecular weight and changing the end-group composition. These results underline the importance of co-polymer composition in the biodegradation of co-polymer systems and highlight the potential use of enzymes for the analytical characterization of synthetic polymers by selectively reducing their molecular weight.