Characterizing the Enzymatic Hydrolysis of Poly-L-Lactic Acid

Abstract

Poly-L-lactic acid (PLLA) and bioplastics alike have a designed degradability to avoid the environmental buildup petro plastics have created. Yet, this designed biotic degradation has typically been characterized in ideal conditions. This study seeks to relate the abiotic to the biotic degradation of PLLA to accurately represent the degradation pathways bioplastics will encounter throughout their life cycle. Enzymatic hydrolysis was used to study the biodegradation of PLLA with varying stages of photo-aging. Utilizing a fluorescent tag to follow enzyme hydrolysis, it was determined that increasing amounts of irradiation yielded greater amounts of total enzymatic hydrolysis by proteinase K after 8 h of enzyme incubation. While photo-aging of the polymers causes minimal changes in chemistry and increasing amounts of crystallinity, the trends in biotic degradation appear to primarily be driven by photo-induced reduction in molecular weight. The relationship between photo-aging and enzyme hydrolysis appears to be independent of enzyme type, though commercial product degradation may be impacted by the presence of additives. Overall, this work reveals the importance of characterizing the biodegradation with relevant samples that ultimately can inform optimization of production and disposal.