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Paper short abstract

Following plastic-degrading enzymes from microbial discovery to industrial hopes, this work shows how scaling challenges in enzymatic recycling are rooted in assumptions that exclude the material specificity of enzyme-plastic interactions in favor of linear claims of transferability.​​​​​​​​​​​​​​​​

Paper long abstract

In recent decades, the discovery of enzymes capable of degrading polyethylene terephthalate (PET), a ubiquitous polymer in packaging and textiles, has generated enthusiasm around enzymatic plastic recycling becoming a circular bioeconomy solution. Yet despite sustained investment on these technologies, they have not reached industrial scale. Arguing the challenges of scaling enzymatic recycling are sociotechnical in nature, this paper asks how the chemical-material qualities of PET-degrading enzymes shift as they move across different scales, and what these transformations reveal about the persistent difficulties of scaling within bioeconomy narratives.

Through a molecule-centered ethnographic approach, this research follows PET-degrading enzymes from microbial discovery to envisioned industrial deployment. It shows how scaling becomes enacted through competing meanings, all of which rest on foundational assumptions about optimization and metabolic equivalence that systematically exclude the contextual complexity of enzyme-plastic interactions. Across academic laboratories, start-ups, and industrial settings, scaling is simultaneously an act of generalization, assuming transferability despite acknowledging material specificity; of quantity, expecting linear and predictable volumetric effects; and of translation, hoping for seamless replacement of existing recycling infrastructures.

By foregrounding (bio)chemical reactions and relations, this work reveals how differing understandings of PET-degrading enzymes are shaped by material transformations that complicate linear promises of scalability, which continuously reconfigure scientific practice, industrial expectations, and sustainability claims around their future use. By doing so, this paper extends existing STS work on the processual nature of substances to industrial enzymology and, ultimately, argues for embracing uncertainty as a necessary condition for thinking toward sustainable futures around emerging biotechnologies.​​​​​​​​​​​​​​​​