Quantification of PET and Nylon Hydrolysis

The release products after enzymatic hydrolysis of PET and nylon were measured via HPLC. To remove protein impurities from the sample, a methanol precipitation step was performed with ice cold methanol (1:1 sample/methanol) (Quartinello et al., 2017 (link)). Afterwards, samples were centrifuged at 12700 rpm for 15 min. at 4°C (5920 R Centrifuge from Eppendorf) followed by an acidification step with 6 N HCl (6 μL per sample). Before pipetting the samples into the HPLC-vials, a filtration step with a 0.45 μM PA filter was performed. For the measurements of the PET released product (Ta), an Agilent LC-MS system was used with a Poroshell 120 column (InfinityLab Poroshell 120 EC-C18, 4.6 × 50 mm, 4 μM, Agilent), a flow of 0.35 mL/min and a non-linear gradient (Table S1). The released products were detected at 241 nm via UV-Vis spectroscopy. Caprolactam released from nylon-6 was measured using an Agilent LC-MS system with a phenomex® column (Aqua® 5 μm C18, 125 Å, LC Column, 250 x 4.6 mm) with an isocratic gradient (H₂O/MeOH, 60/40 [% v/v]) and flow of 0.5 mL/min for 50 min. Hydrolysates were measured at 210 nm via UV-Vis spectroscopy.