Relationships of crystallinity and reaction rates for enzymatic degradation of poly (ethylene terephthalate), PET

Sune W. Schubert, Thore B. Thomsen, Kristine S. Clausen, Anders Malmendal, Cameron J. Hunt, Kim Borch, Kenneth Jensen, Jesper Brask, Anne S. Meyer, Peter Westh*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Biocatalytic degradation of plastic waste is anticipated to play an important role in future recycling systems. However, enzymatic degradation of crystalline poly (ethylene terephthalate) (PET) remains consistently poor. Herein, we employed functional assays to elucidate the molecular underpinnings of this limitation. This included utilizing complementary activity assays to monitor the degradation of PET disks with varying crystallinity (XC), as well as kinetic parameters for soluble PET fragments. The results indicate that a proficient PET-hydrolase, LCCICCG, operates through an endolytic mode of action, and that its activity is limited by conformational constraints in the PET polymer. Such constraints become more pronounced at high XC values, and this limits the density of productive sites on the PET surface. Endolytic chain-scissions are the dominant reaction type in the initial stage, and this means that little or no soluble organic product occurs here. However, endolytic cuts gradually and locally promote chain mobility and hence the density of attack sites on the surface. This leads to an upward concave progress curve; a behavior sometimes termed lag-phase kinetics.
Original languageEnglish
Article numbere202301752
JournalChemSusChem
ISSN1864-5631
DOIs
Publication statusAccepted/In press - 2024

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