Plastic debris has been found in every major ocean and is so pervasive that it is considered a geological indicator of the current era. The commercial advantages of plastics coupled with the environmental issues they produce, has pushed for the development of biodegradable or compostable bioplastics. Poly-L-Lactic Acid (PLLA) is a compostable bioplastic that has begun to replace traditional plastics on the global market. However, with increasing use there is an increasing likelihood of these innovative materials to be improperly disposed of. Thus, the potential accumulation in our terrestrial and aquatic environments increases, where bioplastics will be subjected to a variety of abiotic degradation mechanisms (e.g., photodegradation) that may impact their designed degradability. This work seeks to understand the effects photodegradation has on the biodegradation of PLLA. Specifically, this work uses enzyme hydrolysis as the mode of biodegradation, using hydrolase Proteinase K (ProK) as a model enzyme. Enzymatic degradation of photodegraded PLLA is followed using fluorescence spectroscopy at differing levels of PLLA photoirradiation. Previous work revealed that binding does not correlate to the initial concentration of enzyme in solution and thus enzymatic degradation proceeds at 30µM ProK. To follow this impact of photodegradation on hydrolysis, a fluorogenic probe was added to the PLLA samples and the generation of solution fluorescence is used as an indicator of hydrolysis, with results ongoing. Upon completion of this work, we aim to accurately describe the end-of-life characteristics of PLLA to better mitigate the impact to the environment.

Characterizing proteinase K in the enzymatic hydrolysis of photodegraded polylactic acid

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