Experimental platform for evaluation of the influence of substrate crystallinity on enzymatic degradation of poly(ethylene terephthalate) (PET)

Accumulation of plastics in the environment poses a global environmental threat. Poly(ethylene terephthalate) (PET) is one of the major plastic types, and accounts for 10.2% of the total plastic production [1]. Enzymatic recycling of plastics, such as PET, is a promising technology for a more sustainable use of plastics. However, numerous studies have shown that the activity of PET degrading enzymes is limited on the crystalline regions of PET [2-4]. A pretreatment step is therefore required for efficient enzymatic degradation of PET [3].

Here, we present a new experimental platform for evaluating the influence of the X_C on the enzymatic degradation of PET. We modify the crystallinity of amorphous PET disks in a controlled manner via thermal annealing [2]. The effect of the substrate X_C on the enzyme activity was then evaluated using a novel, compartmentalized UV absorbance assay. This assay enables continuous detection of soluble hydrolysis products released during enzymatic degradation of PET [5]. We show that initial enzymatic treatment (denoted as the lag phase) of PET material does not result in any product formation. The duration of this lag phase, and the steady-state product formation rate did both decreased with increasing X_C.