Kinetic Modeling of the Post-consumer Poly(Ethylene Terephthalate) Hydrolysis Catalyzed by Cutinase from Humicola insolens

The search for a straightforward technology for post-consumer poly(ethylene terephthalate) (PC-PET) degradation is essential to develop a circular economy. In this context, PET hydrolases such as cutinases can be used as bioplatforms for this purpose. Humicola insolens cutinase (HiC) is a promising biocatalyst for PC-PET hydrolysis. Therefore, this work evaluated a kinetic model, and it was observed that the HiC seems not to be inhibited by any of the main PET hydrolysis products such as terephthalic acid (TPA), mono-(2-hydroxyethyl) terephthalate (MHET), and bis-(2-hydroxyethyl) terephthalate (BHET). The excellent fitting of the experimental data to a kinetic model based on enzyme-limiting conditions validates its employment for describing the enzymatic PC-PET hydrolysis using two-particle size ranges (0.075-0.250, and 0.250-0.600 mm) and temperatures (40, 50, 55, 60, 70, and 80 degrees C). The Arrhenius law provided a reliable parameter (activation energy of 98.9 +/- 2.6 kJ mol(-1)) for enzymatic hydrolysis, which compares well with reported values for chemical PET hydrolysis. The thermodynamic parameters of PC-PET hydrolysis corresponded to activation enthalpy of 96.1 +/- 3.6 kJ mol(-1) and activation entropy of 78.9 +/- 9.5 J mol(-1) K-1. Thus, the observed rate enhancement with temperature was attributed to the enthalpic contribution, and this understanding is helpful to the comprehension of enzymatic behavior in hydrolysis reaction.

Automated summary

The study evaluated a kinetic model for the enzymatic hydrolysis of PC-PET using HiC as a catalyst, showing that HiC is not inhibited by major PET hydrolysis products. The experimental data fit well with the kinetic model, validating its use in describing the enzymatic hydrolysis process. The study also provided reliable parameters for the enzymatic hydrolysis, demonstrating the potential of HiC as a biocatalyst for PC-PET degradation in a circular economy.