Plastic-binding peptides as anchors for protein scaffolds on synthetic plastics: opportunities and challenges.

Non-biodegradable synthetic plastics are accumulating in the environment and current recycling methods are limited by harsh processing conditions and inferior quality of recycled products. While biological approaches to plastic degradation offer promise, available enzymes remain inefficient at degrading synthetic plastics due to their inherent physical and chemical properties. Inspired by nature's strategies for degrading resistant natural polymers like cellulose and chitin with enzyme complexes co-localized to polymer surfaces, we quantitatively evaluated a range of previously reported plastic-binding peptides (PBPs) for their capacity to anchor soluble proteins specifically to polystyrene and polypropylene. Among the PBPs tested, LCIM3 demonstrated better specificity when compared to other peptides, binding to polystyrene and polypropylene with an apparent dissociation constant (K D) in the nanomolar range. By analogy to natural cellulosome complexes, we further investigated the rational design of scaffolds utilizing paired dockerin-cohesin protein binding domains and LCIM3 to enable recruitment of multiple user-defined proteins to plastics. Our study demonstrates that plastic binding peptides were marginally able to increase the localization of proteins and scaffolds onto plastic substrates. However, we also identify a significant non-specific adsorption of many untargeted proteins on plastic as a potential bottleneck for approaches to improve plastic degradation via rational engineering. This proof-of-concept study highlights both the opportunities and challenges in designing bio-inspired scaffolds to improve plastic degradation, laying a foundation for future advancements in sustainable plastic recycling and upcycling.