An engineered enzyme embedded into PLA to make self-biodegradable plastic.

Abstract

Plastic production reached 400 million tons in 2022 (ref. ¹), with packaging and single-use plastics accounting for a substantial amount of this². The resulting waste ends up in landfills, incineration or the environment, contributing to environmental pollution³. Shifting to biodegradable and compostable plastics is increasingly being considered as an efficient waste-management alternative⁴. Although polylactide (PLA) is the most widely used biosourced polymer⁵, its biodegradation rate under home-compost and soil conditions remains low^6-8. Here we present a PLA-based plastic in which an optimized enzyme is embedded to ensure rapid biodegradation and compostability at room temperature, using a scalable industrial process. First, an 80-fold activity enhancement was achieved through structure-based rational engineering of a new hyperthermostable PLA hydrolase. Second, the enzyme was uniformly dispersed within the PLA matrix by means of a masterbatch-based melt extrusion process. The liquid enzyme formulation was incorporated in polycaprolactone, a low-melting-temperature polymer, through melt extrusion at 70 °C, forming an 'enzymated' polycaprolactone masterbatch. Masterbatch pellets were integrated into PLA by melt extrusion at 160 °C, producing an enzymated PLA film (0.02% w/w enzyme) that fully disintegrated under home-compost conditions within 20-24 weeks, meeting home-composting standards. The mechanical and degradation properties of the enzymated film were compatible with industrial packaging applications, and they remained intact during long-term storage. This innovative material not only opens new avenues for composters and biomethane production but also provides a feasible industrial solution for PLA degradation.