Mechanistic study of enzymatic hydrolysis of poly(butylene succinate)/poly(pentamethylene 2,5-furanoate)-based blend and block copolymer

Poly(butylene succinate)(PBS) and poly(pentamethylene 2,5-furanoate)(PPeF) are bio-based polymers that proved to be compatible to derive versatile blends. The different mechanical properties resulting from their combinations respond to the diverse needs in food packaging. While already their physical blending lead to products with good flexibility, copolymers showed further improved elasticity while maintaining good gas barrier properties. The possibility of being fully degraded through hydrolytic enzymes places an additional advantage to the fully green potential of these polymers. The two homopolymers, their physical blend as well as copolymer were demonstrated to be decomposed by the Humicola insolens cutinase (HiC) reaching 100 % of weight loss after 24 h of incubation. PBS was hydrolysed faster than PPeF, while, interestingly, at 50 % content of each polymer, the physical blend was more susceptible to enzymatic hydrolysis than the copolymer, as resulted from weight loss and HPLC quantification of the released monomers. This trend was even more pronounced related to reduction of molecular weight during the first phase of hydrolysis as indicated by Gel Permeation Chromatography analysis. Surface characterization of the polymers during hydrolysis by using Fourier Transform Infrared Spectroscopy likewise confirmed faster hydrolysis of PBS moieties. Nuclear Magnetic Resonance highlighted slower appearance of hydrolysis-related groups in the copolymer when compared to the physical blend. Overall, this mechanistic study indicates that blending or synthetizing copolymers can influence enzymatic hydrolysis with important implications towards exploitation of enzymes as an environmentally benign emerging technology for recycling.