Chemo-Enzymatic Depolymerization of Functionalized Low-Molecular-Weight Polyethylene

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon-carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low-molecular-weight (LMW) PE using an enzyme cascade that included a catalase-peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m-chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram-scale pretreated polymers, GC-MS and weight loss determinations confirmed ~27 % polymer conversion including the formation of medium-size functionalized molecules such as ω-hydroxycarboxylic acids and α,ω-carboxylic acids. Additional analyses of LMWPE-nanoparticles using AFM showed that enzymatic depolymerization reduced the sizes of these mCPBA- and enzyme-treated LMWPE-nanoparticles. This multi-enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio-based recycling methods for polyolefin waste.