Lakshmiprasad Gurrala; Rafi Anowar; Ana Rita C. Morais

DOI:

Abstract

Enzymatic hydrolysis of semicrystalline (PET) is hindered by the hydrophobic nature and crystallinity of the substrate, and it highly depends on the available interfacial area between substrate and aqueous phase. While most studies leverage particle size reduction to increase interfacial area, this study investigates the use of supercritical CO2 (scCO2) to increase internal surface area in PET, and its impact on the enzymatic hydrolysis yields. Our work shows that scCO2 pretreatment of semicrystalline PET resulted in up to 2-fold higher (TPA) yield relative to the untreated counterpart using Humicola insolens cutinase (HiC) enzyme. There is a positive correlation between the total pore surface area in the scCO2-pretreated PET samples and the final yield. In addition, preliminary kinetic studies revealed faster initial production of for scCO2-treated PET relative to untreated PET. ScCO2-treated PET samples showed no significant changes in the crystalline content and thermal properties. However, NMR data indicated that scCO2-treated PET has a slightly higher apparent number-average molecular weight (Mn) relative to that of untreated PET. Overall, scCO2 pretreatment led to increased semicrystalline PET susceptibility to HiC enzyme action, resulting in increased yields.

Keywords

biocatalysis ; acid ; CO2 ; porosity ; cutinase ; interfacial ; sustainability ; plastic recycling/upcycling

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