Enzyme-programmed cellulose nanocrystal interfaces: Regulating degradation microenvironment and plant growth of polylactic acid films

Petroleum-based plastics are a significant source of global environmental pollution due to their non-biodegradability. Polylactic acid (PLA), a bio-based and biodegradable polymer, appears to be a promising alternative. However, PLA’s slow degradation rate and formation of persistent residues limit its practical application in agriculture. PLA breakdown can be accelerated by designing stable catalysts, such as through immobilization strategies. Enzyme supports can microregulate the surrounding microenvironment, thereby enhancing enzyme–substrate interactions. Herein, we first design an enzyme–cellulose nanocrystal interface to regulate the microenvironment for the degradation of polylactic acid (PLA) films. By grafting Proteinase K (ProK) onto carboxylated cellulose nanocrystals (HSCNC) and incorporating the resulting Pro-HSCNC into PLA matrix, a composite (PCPro) was developed that demonstrates enhanced crystallinity and mechanical strength while preserving ProK enzymatic activity. The Pro-HSCNC not only introduces multiple degradation sites effectively but also enhances water retention and microbial growth, thereby actively managing the local environment to enable faster, controlled degradation. As a result, PCPro reaches up to 29.5% degradation in soil within 120 days while also supporting plant growth, surpassing most PLA composites in degradation performance. Life cycle assessment (LCA) of PCPro shows a significantly lower environmental impact compared to conventional PLA. This work introduces a new approach for designing enzyme-active bio-polyester-based materials with programmable degradation behaviors through enzyme–cellulose interfacial interaction.