Background
Plastics have been widely used due to their light weight, durability, and low cost. However, their poor degradability has led to an escalating global pollution crisis. According to United Nations Environment Programme (UNEP) and Organisation for Economic Co-operation and Development (OECD) statistics, approximately 20 million tons of plastic waste enter aquatic environments every year, while the recycling rate remains below 9%, posing severe threats to ecosystems worldwide.
Among them, polyester plastics—such as PET, PBAT, and PLA—stand out for their excellent mechanical and chemical properties. With annual production reaching hundreds of millions of tons, they are extensively applied in packaging, fisheries, and aquaculture. Although ester bonds are theoretically biodegradable, the highly ordered and rigid molecular structures of polyesters make them extremely resistant to natural degradation—especially under low-temperature, high-pressure marine conditions, where degradation is almost impossible. Consequently, polyesters have become a core challenge in marine plastic pollution.
Over time, these non-degradable plastics fragment into microplastics smaller than 5 mm in diameter. These particles accumulate along the food chain and have even been detected in the human bloodstream, as reported by Dutch researchers in 2022—providing the first direct evidence that plastic pollution poses an immediate threat to human health.
Current physical, chemical, and biological treatment methods for polyester degradation still suffer from major drawbacks, including poor sustainability, high cost, secondary pollution, low catalytic efficiency, and limited environmental adaptability, all of which restrict their large-scale application.
Project Overview
To address the persistence of polyester plastics in marine environments, our team employed synthetic biology techniques—including enzyme mining and rational enzyme engineering—to develop a marine-derived polyester hydrolase with broad substrate specificity, high catalytic activity, and enhanced thermal stability.
Based on this enzyme, we designed a two-way strategy that integrates source-level biodegradability with end-of-pipeline microplastic management.
At the source level, we focused on overcoming one of the fundamental bottlenecks of polyester degradation: the surface-limited catalysis of hydrolases. Because enzymatic hydrolysis occurs only at the polymer surface and is strongly influenced by environmental factors, degradation under industrial conditions often remains inefficient and incomplete.
To solve this, we developed an enzyme immobilization system using an inorganic calcium carbonate–silicon dioxide nanocomposite as the carrier. This immobilization approach significantly enhances enzyme thermostability—allowing the hydrolase to remain active near the melting temperature of polyesters. Consequently, the enzyme can be embedded directly into polyester materials during industrial processing, effectively transforming traditionally non-degradable plastics into biodegradable materials under ambient conditions. At the same time, the use of low-cost, commonly available mineral fillers ensures economic feasibility, process compatibility, and environmental sustainability.
We also calculer the cost of our enzymatic angent，comparing with other mature processing methods as below.
At the end-of-life stage, we designed a microplastic enrichment and degradation system based on the same efficient hydrolase. This system enables the capture and enzymatic decomposition of ester-based microplastics in aquatic environments. Additionally, by detecting the hydrolysis products, it provides a means to quantitatively assess polyester pollution levels in water.
In the future, we aim to integrate degradation and detection capabilities using synthetic biology tools to develop an intelligent whole-cell biosensor capable of simultaneously monitoring and degrading microplastics. This represents a significant step towards building an autonomous, controllable, and responsive bioremediation system for plastic pollution.
Through the development of a two-way biotechnological strategy, our team has enhanced the biodegradability of polyesters at the source while addressing the "last mile" of ester-based plastic pollution management. This integrated approach offers a sustainable and scalable solution to global polyester pollution, achieving green governance across the entire life cycle of polyester plastics.
References
[1] UNEP. (2025). Plastic pollution & marine litter: Facts and figures. United Nations Environment Programme. “Every year, 19-23 million tonnes of plastic waste leak into aquatic ecosystems.”
[2] OECD. (2022). Global Plastics Outlook: Economic Drivers, Environmental Impacts and Policy Options. Organisation for Economic Co-operation and Development. “Only 9% of plastic waste is recycled globally.”
[3] De Luca, S., et al. (2023). Poly(lactic acid) and Its Blends for Packaging Application. MDPI.
[4] ExpertMarketResearch. (2024). Polybutylene Adipate Terephthalate (PBAT) Market: Analysis & Outlook.
[5] Pagnotta, L., et al. (2025). Sustainable Netting Materials for Marine and Agricultural Applications. MDPI.
[6] Lee, S., Kim, H., & Park, J. (2024). Biodegradation behavior of polyesters with various internal chemical structures and external environmental factors in real seawater. Polymer Testing, 132, 108357.
[7] Smith, A., & Zhao, L. (2023). Chemical control of polyester hydrolysis: role of crystallinity and chain packing. Chemical Science.
[8] Leslie, H. A., van Velzen, M. J. M., Brandsma, S. H., Vethaak, A. D., Garcia-Vallejo, J. J., & Lamoree, M. H. (2022). Human blood contains microplastics. Environment International, 159, 107027.
[9] Vethaak, A. D., & Leslie, H. A. (2022). Microplastics in blood — first detection in healthy humans. Vrije Universiteit Amsterdam (Immunoplast project).
[10] Zhang, X., Li, Y., Wang, P., & Chen, L. (2024). Catalytic Depolymerization of Polyester Plastics Toward Closed-Loop Recycling and Upcycling. Green Chemistry.
[11] Liu, H., Sun, Q., & Zhao, M. (2024). Upcycling of Waste Polyesters for the Development of a Circular Economy. RSC Communications.
[12] Singh, A., Patel, R., & Kumar, S. (2024). Advances in Catalytic Chemical Recycling of Synthetic Textiles. Green Chemistry.
[13] Wang, J., Li, F., & Zhao, Y. (2024). Enzymatic Degradation of Synthetic Plastics by Hydrolases/Oxidoreductases. International Biodeterioration & Biodegradation.
[14] Yue, W.; Robert, J.; Albert, T.; et al. Polyester Biodegradability: Importance and Potential for Optimisation. Green Chem. 2024, 26 (7), 3698–3716. DOI: 10.1039/d3gc04489k.
[15] Chan Hee, L.; Hye Sun, L.; Jae Won, L.; et al. Evaluating Enzyme Stabilizations in Calcium Carbonate: Comparing In Situ and Crosslinking Mediated Immobilization. Int. J. Biol. Macromol. 2021, 175, 341–350.
[16] Hu, J.; Chen, Y. Constructing Escherichia coli Co-Display Systems for Biodegradation of Polyethylene Terephthalate. Bioresour. Bioprocess. 2023, 10 (1), 91.
[17] Linxiang, L.; Abe, Y.; Nagasawa, Y.; et al. An HPLC Assay of Hydroxyl Radicals by the Hydroxylation Reaction of Terephthalic Acid. Biomed. Chromatogr. 2004, 18 (7), 470–474.