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Ester bond pre-activation for high-efficiency biodegradation: A self-reinforcing degradation strategy for PET via an evolved bacterium
Summary
Scientists evolved a special bacterium that can break down PET plastic (used in bottles and clothing) even in harsh, alkaline wastewater, the kind found in some industrial runoff, where normal plastic-eating microbes can't survive. This matters because it offers a gentler, more sustainable way to clean up plastic pollution at its source, potentially reducing the amount of PET and microplastics that end up contaminating water, soil, and eventually our food and bodies.
Polyethylene terephthalate (PET) is a hazardous environmental contaminant that contributes to both plastic and microplastic pollution, with its biodegradation severely limited by the kinetic stability of ester bonds-particularly in alkaline industrial wastewater (pH 9-11) where most known biocatalysts are inactive. To overcome this, evolutionary engineering was employed to construct a whole-cell biocatalyst for alkaline environments. Through UV-LiCl mutagenesis and adaptive laboratory evolution, an alkaline-adapted Comamonas testosteroni strain F6 was developed, thriving at pH 10 with PET as sole carbon source. Strain F6 increased weight loss from 2.4% to 6.1% in 3 days and accelerated terephthalic acid release versus the wild-type under neutral conditions. This improvement arises from a synergistic mechanism: alkaline conditions chemically pre-activate ester bonds, and the released monomers fuel microbial growth and enzyme secretion, establishing a self-reinforcing degradation cycle. This feedback-driven process caused severe surface erosion, reducing fiber diameter from 20.2 to 18.1 μm. The system operates at mild pH 10 and 37 °C with a self-moderating effect that partially neutralizes alkalinity, contrasting with harsh chemical hydrolysis (pH >13, high temperature). This work provides a theoretical basis for using substrate pre-activation and evolved biocatalysis to treat PET-contaminated alkaline industrial effluents.