Polyurethanes (PUs) are a highly versatile class of synthetic polymers with broad industrial applications as foams, coatings, and adhesives. PUs are known for their resistance against biodegradation and are usually designed for long-term usage. Particularly in application areas such as agriculture and forestry, in which products cannot be collected after use, biodegradability becomes key to avoid environmental pollution. This study reports on the successful embedment of active cutinases into thermoplastic PU (TPU) by a solvent-based approach to accelerate TPU degradation at ambient conditions (37 °C). Embedded cutinases efficiently degrade TPU as determined by the release of the degradation product adipic acid and cutinase activity was confirmed by weight loss of cutinase-containing TPU films. In absence of a cutinase no monomer release was detected over the whole incubation period of 21 days. Embedded cutinases accelerate TPU degradation by up to 1.6-fold over externally supplemented cutinases; this highlights the superior degradation performance of embedded cutinases. Of the five cutinases investigated, two had been previously deemed unsuitable for heat-based embedment. Remarkably, these two cutinases retained nearly one third of the TPU degradation activity of the best-performing cutinase (HiC) after solvent-based embedding. In essence, these results show that solvent-embedment expands the potential use of cutinases in PU degradation and represents a complementation of heat-based extrusion processes.
Knopp et al. (Sun,) studied this question.