Directed evolution of material binding peptide for polylactic acid-specific degradation in mixed plastic wastes

  Yi Lu Copyright: © biotec

Lu, Y., Hintzen, K. W., Kurkina, T., Ji, Y., Schwaneberg, U., ACS Catalysis.

Material binding peptide (MBP) Cg-Def was engineered by KnowVolution campaign and the generated variant Cg-Def YH (L9Y/S19H) showed 2.0-fold improved polylactic-acid (PLA) binding specificity from polystyrene (PS). The fusion of Cg-Def YH with PLA degrading enzyme confirmed the enhanced PLA degradation (twice as high as the enzyme only) in mixed PLA/PS plastics.

Plastics are widely used in our daily life and have a large amount of production. Commercially used plastics mainly comprise polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), and polyurethane (PU), and they are mostly produced from fossil fuels. Management of plastic wastes to reduce their risks to living organisms and humans is important. Addressing the risks associated with climate change, researchers advocate for a shift from conventional petrochemical-based plastics to bioplastics sourced from renewable materials, alongside the implementation of circular economy strategies. Polylactic acid (PLA), a polyester produced from renewable sources such as starch or sugar, is from its performance an attractive bioplastic. PLA is often blended with other petrochemical polymers like poly(ε-caprolactone) (PCL), polybutylene succinate (PBS), thermoplastic starch (TPS), PE, PP, and PS, to optimize hydrophobicity, mechanical behavior, and reduce production costs. Here, a concept demonstrates accelerated PLA degradation in a mixed suspension of PLA and PS nanoparticles using an engineered material binding peptide (MBP). After comparing the PLA binding performance of 20 MBPs, Cg-Def was selected for its potential PLA binding specificity. Subsequently, a robust high-throughput screening system was developed to enhance material-specific binding of Cg-Def to PLA in the presence of PS. With KnowVolution campaign, a variant, Cg-Def YH (L9Y/S19H), with a 2.0-fold improved PLA binding specificity compared to PS is generated. Contact angle and surface plasmon resonance measurements confirm the improved surface coverage of Cg-Def YH on the PLA surface. The fusion of Cg-Def YH with a PLA degrading enzyme accelerates PLA degradation (twice as effective compared to using the enzyme alone) in mixed PLA/PS plastics.

Yi Lu is financially supported by the China Scholarship Council (CSC) scholarship. This work was supported by European Union's Horizon 2020 research and innovation program under grant agreement no. 870294 for the project MIX-UP.

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Lu, Y., Hintzen, K. W., Kurkina, T., Ji, Y., Schwaneberg, U., ACS Catalysis.

  PLA-specific degradation Copyright: © ACS Catalysis

Figure 1. PLA-specific degradation in PLA/PS mixed plastics with the assistance of engineered MBPs. Through the KnowVolution strategy, engineered Cg-Def variant possesses improved PLA binding specificity compared to PS, and thereby enhancing PLA degradation in PLA/PS mixed plastic waste. (PLA: polylactic acid; MBPs: material binding peptides; PS: polystyrene).