INSIGHTS INTO THE ENZYMATIC HYDROLYSIS OF PEF USING POLYESTER HYDROLASES

PEF is considered to be the next-generation green polyester and a rising star among novel plastics. It is biobased, nontoxic, and has improved barrier properties compared to PET. Moreover, biobased PEF offers lower life-cycle greenhouse gas emissions than PET. However, with its industrial production starting soon, relatively little is known about its actual recyclability. Our study showed nearly complete depolymerization of PEF using FastPETase and leaf compost-cutinase (LCC), at loadings 4.5−17 times lower than previously reported. Maximum depolymerization of PEF, measured by weight loss and 2,5-furandicarboxylic acid (FDCA) production, was reached incubating FastPETase or LCC with potassium phosphate−NaOH buffer at 50 and 65 °C, respectively. 98% depolymerization of 13 g L−1 PEF film was achieved by three additions of the LCC in 72 h, while 78% weight loss was obtained using FastPETase. Nonetheless, 92% weight loss was obtained with FastPETase when using only 6 g L−1 PEF. The main reaction products were identified as FDCA, ethylene glycol, and mono(2-hydroxyethyl)-furanoate. LCC performed better than FastPETase, in terms of both FDCA release and weight loss. The effect of crystallinity was evident on the enzymes’ performance, as only 4% to 7% weight loss of crystalline PEF (32%) was recorded. To further elucidate the enzyme’s mode of action, we have now synthesized different PEF oligomers (such as BHEF and MHEF) to understand eventual product inhibition and activity on these monomers. We will characterize the kinetics of PET-hydrolyzing enzymes in various conditions to get deeper insights into PEF hydrolysis. The interaction between enzyme and reaction products (BHEF, MHEF, FDCA, and EG) will be evaluated using NMR spectroscopy (2D NMR) to monitor product release in real-time. This will enhance our understanding and suggest future approaches to improve enzymatic PEF hydrolysis.
Keywords: PEF, Polyester hydrolase, 2D NMR, MHEF, BHEF, Kinetics