Assessing biological degradation of non-hydrolysable synthetic polymers

The discovery and engineering of enzymes capable of depolymerizing synthetic polymers with hydrolysable backbone linkages is now enabling biotechnological solutions for plastics recycling. Polyolefins and other non-hydrolysable polymers, however, have saturated carbon-carbon linkages that are more challenging to cleave biologically. Despite decades of research, the evidence that biocatalysts can appreciably deconstruct carbon-carbon-linked polymers remains ambiguous, often stemming from inconsistent assays and qualitative, low-resolution analytical methods and from the lack of proper identification and biochemical characterization of the enzymes involved. To aid in definitive polymer deconstruction measurements for non-hydrolysable polymers, here we survey abiotic and biological oxidation mechanisms and provide critical commentary on experimental assays and substrate and product characterization approaches. From this foundation, we propose best-practice experimental design principles, including reaction conditions, control experiments, analytical approaches, biochemical assays and characterization methods that should promote reproducibility and impact across this field.