Cutinase-Catalyzed Hydrolysis of Poly(ethylene terephthalate)

A detailed study and comparison was made on the catalytic activities of cutinases from Humilica insolens (HiC), Pseudomonas mendocina (PmC), and Fusarium solani (FsC) using low-crystallinity (lc) and biaxially oriented (bo) poly(ethylene terephthalate) (PET) films as model substrates. Cutinase activity for PET hydrolysis was assayed using a pH-stat to measure NaOH consumption versus time, where initial activity was expressed as units of micromoles of NaOH added per hour and per milliliter of reaction volume. HiC was found to have good thermostability with maximum initial activity from 70 to 80 °C, whereas PmC and FsC performed best at 50 °C. Assays by pH-stat showed that the cutinases had about 10-fold higher activity for the lcPET (7% crystallinity) than for the boPET (35% crystallinity). Under optimal reaction conditions, initial activities of cutinases were successfully fit by a heterogeneous kinetic model. The hydrolysis rate constant k2 was 7-fold higher for HiC at 70 °C (0.62 μmol/cm2/h) relative to...