Surface-immobilized microalgal biohybrid system with dual-specificity enzyme scaffold for enhanced PET degradation and adaptive algal responses in aquatic environments

초록

Polyethylene terephthalate (PET) is a widely used polymer whose environmental accumulation remains problematic due to its resistance to natural degradation. While conventional recycling and upcycling methods are available, they often suffer from high energy demands and limited efficiency. Biologically integrated strategies offer a promising alternative, enabling low-energy plastic conversion under environmentally benign conditions. In this study, we developed a biohybrid construct by immobilizing an engineered plastic-degrading enzyme complex (ePDEC) onto the surface of Chlorella vulgaris, facilitating sustained PET depolymerization under environmentally relevant conditions. The ePDEC, comprising a PETase variant and dual carbohydrate-binding modules, enhanced adhesion to both algal surfaces and PET films, improving binding efficiency by 80 % and terephthalate (TPA) release by 2.5-fold compared to the wild-type PETase. When immobilized on C. vulgaris, PET degradation efficiency increased 4.0-fold relative to the free enzyme, resulting in a 4 % reduction in PET mass under laboratory conditions. In parallel, algal biomass accumulation, chlorophyll production (6.3 mu g/mL for chlorophyll a; 4.0 mu g/mL for chlorophyll b), and stress-responsive gene expression were all significantly elevated. Environmental validation using freshwater from the Seongbuk Stream demonstrated a 7 % PET mass reduction, confirming the functionality of the construction under realistic conditions. This study presents a dual-functional strategy that unites plastic biodegradation and algal valorization, offering a promising route for sustainable bioremediation and bioproduct generation beyond the limitations of current recycling approaches.

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