Abstract
A series of copolyesters based on furanic acid and sulfonated isophthalic acid with various polyols were synthetized and their susceptibility to enzymatic hydrolysis by cutinase 1 from Thermobifida cellulosilytica (Thc_Cut1) investigated. All copolyesters consisted of 30 mol % 5-sulfoisophthalate units (NaSIP) and 70 mol % 2,5-furandicarboxylic acid (FDCA), while the polyol component was varied, including 1,2-ethanediol, 1,4-butanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, or tetraethylene glycol. The composition of the copolyesters was confirmed by 1H-NMR and the number average molecular weight (Mn) was determined by GPC to range from 2630 to 8030 g/mol. A DSC analysis revealed glass-transition temperatures (Tg) from 84 to 6 °C, which were decreasing with increasing diol chain length. The crystallinity was below 1% for all polyesters. The hydrolytic stability increased with the chain length of the alkyl diol unit, while it was generally higher for the ether diol units. Thc_Cut1 was able to hydrolyze all of the copolyesters containing alkyl diols ranging from two to eight carbon chain lengths, while the highest activities were detected for the shorter chain lengths with an amount of 13.6 ± 0.7 mM FDCA released after 72 h of incubation at 50 °C. Faster hydrolysis was observed when replacing an alkyl diol by ether diols, as indicated, e.g., by a fivefold higher release of FDCA for triethylene glycol when compared to 1,8-octanediol. A positive influence of introducing ionic phthalic acid was observed while the enzyme preferentially cleaved ester bonds associated to the non-charged building blocks.
Highlights
There is an increasing interest in replacing petroleum-based raw materials by renewable bio-based resources in polymer production [1,2,3,4]
We have recently demonstrated the enzymatic hydrolysis of poly(ethylene furanoate) (PEF) by cutinase 1 from
The aims of this study were to synthesize copolyesters based on 5-sulfoisophthalic acid and 2,5-furandicarboxylic acid with altering alkyl and ether diols to investigate their influence on hydrolytic stability and enzymatic hydrolysis
Summary
There is an increasing interest in replacing petroleum-based raw materials by renewable bio-based resources in polymer production [1,2,3,4]. The introduction of ionic moieties can, for example, be used to improve the dyeability of textile fibers, create delivery systems for charged proteins and drugs, shape memory polymers and self-healing polymers, improve the properties of soil-releasing agents and textile-sizing agents, or to increase the hydrolytic degradation rate of polymers when desired [16]. For this purpose, frequently sulfonated monomers are introduced into polyesters, which have been extensively investigated regarding their impact on viscosity, crystallinity, mechanical properties, and hydrolytic stability [17,18,19]
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