Enhanced biodegradation of polylactic acid by Aspergillus oryzae lipase: Toward sustainable plastic end-of-life solutions

This study investigates the enhanced biodegradation of polylactic acid (PLA) films and microparticles using a commercial lipase enzyme from Aspergillus oryzae. To evaluate the effect of pH on the bioprocess efficiency, the enzymatic hydrolysis of PLA films was initially examined at pH values ranging from 7.0 to 8.5, at 37℃, for 28 days, using an enzyme activity of 2,425 U/mL. Changes in the surface morphology and chemical structure of the films were more pronounced at pH 8.0, while it was found that the lipase preferentially targets the amorphous regions of PLA, leaving its crystalline structures intact during the treatment period. The treated PLA films exhibited significant alterations in their surface morphology, with enhanced roughness and increased hydrophilicity compared to the untreated films. Using pH 8.0 as the optimum condition, the effect of higher lipase enzyme activities on the biodegradation of both PLA films and microparticles was studied, showing a clear acceleration in enzymatic hydrolysis. Additionally, the production of lactic acid during the degradation process was confirmed through high-performance liquid chromatography. These findings highlight the potential of enzymatic approaches to efficiently degrade PLA-based materials, enabling their bioconversion into valuable lactic acid monomers. By addressing the end-of-life challenges of PLA, this work demonstrates its viability as a sustainable alternative to conventional plastics, contributing to a circular economy and reducing environmental impact.