Photoelectrocatalytic biosynthesis fuelled by microplastics

Biocatalytic artificial photosynthesis integrates photocatalysis and redox biocatalysis to synthesize value-added chemicals using solar energy. However, this nature-inspired approach suffers from sluggish rates of reaction because of challenging water oxidation kinetics. Here we report photoelectrochemical biosynthetic reactions that use non-recyclable real-world poly(ethylene terephthalate) (PET) microplastics as an electron feedstock. A Zr-doped haematite photoanode extracts electrons from hydrolysed PET solutions obtained from post-consumer PET waste, such as drinks bottles, and transfers the electrons to the bioelectrocatalytic site. Carbon-based cathodes receive the electrons to activate redox enzymes (for example, unspecific peroxygenase, L-glutamate dehydrogenase and ene-reductase from the old yellow enzyme family) that drive various organic synthetic reactions. These reactions include oxyfunctionalization of C–H bonds, amination of C=O bonds and asymmetric hydrogenation of C=C bonds. These photoelectrocatalytic–biocatalytic hybrid reactions achieve total turnover numbers of 362,000 (unspecific peroxygenase), 144,000 (L-glutamate dehydrogenase) and 1,300 (old yellow enzyme). This work presents a photoelectrocatalytic approach for integrating environmental remediation and biocatalytic photosynthesis towards sustainable solar-to-chemical synthesis. Plastic waste poses a serious economic, ecological and environmental threat. Here, non-recyclable, post-consumer microplastics are used as an electron feedstock for biosynthetic reactions in a photoelectrocatalytic system. The microplastics are simultaneously broken down into organic fuels, meaning that this system provides valuable chemicals at both the anodic and cathodic sites.