Analysis of the product-spectrum during the biocatalytic hydrolysis of PEF (poly(ethylene furanoate)) with various esterases†

Abstract

Poly(ethylene furanoate) (PEF) is considered the greener alternative to poly(ethylene terephthalate) (PET) and other plastics, as it can be produced 100% biobased from renewable resources based on the building blocks 2,5-furandicarboxylic acid (FDCA) and ethylene glycol (EG). So far, most of the literature has dealt with the synthesis and detailed characterization of this synthetic polymer, but very few articles deal with enzymatic depolymerization, which is increasingly favored due to environmental reasons. This study therefore aimed to perform hydrolysis of Nano-PEF using 12 different esterases, which have been shown to depolymerize PET very efficiently. All enzymes were compared in terms of their hydrolysis efficiency, showing very different hydrolysis rates and different product profiles over time. A wide variety of hydrolysis products were identified using ESI-TOF including FDCA, (mono(2-hydroxyethyl)-furanoate) (MHEF), (bis(2-hydroxyethyl)-furanoate) (BHEF), dimers, and trimers. Among the tested enzymes, LCC^ICCG was the most efficient one performing best at pH 8–9 and elevated temperatures (>70 °C). Finally, all hydrolysis intermediates were hydrolyzed to the final building block FDCA (>99% with almost complete depolymerization of Nano PEF), and higher Nano-PEF-concentrations (up to about 1.4 mg mL⁻¹) were depolymerized equally efficient.