Enzymatic depolymerization of highly crystalline polyethylene terephthalate enabled in moist-solid reaction mixtures
Sandra Kaabel, J. P. Daniel Therien, Catherine E. Deschênes, Dustin Duncan, Tomislav Friščić, Karine Auclair
Abstract
Significance Although polyethylene terephthalate (PET) is the most recycled plastic, its recycling typically involves thermomechanical means, producing a plastic of lower quality that cannot be recycled again. In contrast, breaking PET down to its building blocks allows for repolymerization into high-quality PET. Chemical depolymerization of PET requires hazardous chemicals and conditions. Enzymes are environmentally benign, renewable catalysts that work under mild conditions. Several enzymes capable of depolymerizing low-crystallinity PET have been reported; however, efficient depolymerization of highly crystalline forms of PET typically found in consumer products has remained elusive. Here, we report that, in moist-solid reaction mixtures, the cutinase from Humicola insolens can efficiently hydrolyze highly crystalline PET to terephthalic acid with a 50% yield, without any amorphization or pretreatment of PET.