Post-consumer recycled polyethylene terephthalate (RPET) flakes were extruded into strands (ex-RPET) then enzymatically degraded using an unpurified Leaf Compost Cutinase (LCC) enzyme cocktail to better understand the effect of material properties on the degradation behavior of PET. Specific surface area [m²g^-1], a property that is tied to substrate form factor, was investigated to determine its influence on PET degradation rate. At low specific surface area, an initial lag phase was observed where little to no degradation occurred up until a takeoff point (1-2 days) after which degradation proceeded at velocities typical of the set experimental parameters. As specific surface area was increased, the lag phase gradually decreased (< 1 day) and degradation began at earlier times. Substrate surfaces at early time points were unchanged for the most part, sporting only a few defects and holes. As degradation time increased, holes grew larger where present, suggesting that an enzyme would find a location to bind to and degradation would spread from the binding site. This observation is in agreement with other studies which have sought to understand the binding behavior of PET degrading enzymes (e.g. PETase, TfCut2, etc.). The cost tradeoff of manually increasing surface area versus allowing the enzyme to create its own surface area was explored. The results of this work better inform the recycling community on the effects and costs of processing parameters.

Various substrates sizes of recycled PET substrates degraded by <i>Leaf Compost Cutinase</i> enzymes were examined. The effects and costs of processing parameters were explored and reported.

Various substrates sizes of recycled PET substrates degraded by Leaf Compost Cutinase enzymes were examined. The effects and costs of processing parameters were explored and reported.

Professor Margaret Sobkowicz

Professor, University of Massachusetts Lowell

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