Microbial and Enzymatic Biodegradation of Polyurethane: From Depolymerization to Monomer Valorization

Polyurethane (PU), as one of the most widely produced and consumed plastics globally, has led to severe environmental pollution and resource wastage due to the substantial amount of solid waste and microplastics it generates. Plastic recycling technologies that employ microorganisms and enzymes as catalysts not only enable efficient depolymerization of PU wastes into monomers while offering notable advantages, such as mild reaction conditions and avoidance of organic solvents. These features position enzymatic and microbial processes as a promising solution for achieving green and low-carbon end-of-life treatment of PU. However, PU biodegradation technologies are still in the early stages of fundamental research and face multiple challenges, including limited biocatalytic resources, low efficiency of enzymatic depolymerization, and difficulties in recovery and reuse. This review systematically summarizes the chemical structures of PU, recent advances in PU-degrading microbes and enzymes. It further discusses the biological metabolic pathways of depolymerized monomers, as well as current resource utilization strategies via closed-loop recycling and upcycling. The aim of this review is to provide theoretical guidance and novel insights into the efficient biodegradation and recovery of PU, thereby supporting the development of a circular plastic economy and contributing to global sustainability and carbon neutrality goals.