The degradation of PLA was confirmed by 1H-NMR and 13C-NMR spectroscopy. For each sample, 6 mg of the solid product was dissolved in 0.5 mL of deuterated chloroform (CDCl3). The 1H-NMR and 13C-NMR spectra were recorded with a Varian (Palo Alto, CA, USA) NMRS-500 and MR-400 MHz NMR spectrometer operating at 500 and 400 MHz. The spectra were processed using MestReNova software (version 14.2.0-26256).