Degradation of PET microplastic particles to monomers in human serum by designer enzymes

<title>Abstract</title> Due to prolonged exposure, microplastic particles are found in human blood and other bodily fluids. Despite a lack of toxicity studies regarding microplastics, harmful effects for humans seem plausible and cannot be excluded. As small plastic particles readily translocate from the gut to body fluids, enzyme-based treatment of serum could constitute a promising avenue to clear synthetic polymers and their responding oligomers by degradation into monomers. Still, the activity of plastic degrading enzymes in serum remains unknown. Here we report how engineered PETases can depolymerize microplastic-like particles of the commodity polymer polyethylene terephthalate (PET) into its non-toxic monomer terephthalic acid (TPA) in human serum at 37°C. By developing an efficient method to depolymerize microplastics <italic>in vitro</italic> , our work takes a step closer to find a solution to the problem that microplastics in the bloodstream may pose in the future.