Molecular insights into polyurethane biodegradation in <i>Pseudomonas protegens</i>

The polyurethane (PU) market is projected to reach $94 billion USD by 2028 and spans many industries, including automotive, construction, medical, furniture, and fashion. However, less than 30% of PU plastics are recycled, with the remainder going to landfill. The inherent recalcitrant nature of PU makes it challenging to study naturally occurring routes of PU degradation, like microbial biodegradation and its underlying genetic mechanisms. To address this, we developed a high-throughput screening method using transposon-directed insertion site sequencing (TraDIS) on the known PU-degrading strain <i>Pseudomonas protegens</i> Pf-5. This approach identified a key global regulatory gene (GacS), the mutant of which acts as a "hyperdegrader" with a faster PU degradation rate. Subsequent transcriptomic and phenotypic analyses revealed an unsuspected PU-degradation mechanism involving a siderophore-mediated Fenton reaction. These findings highlight the importance of using high-throughput functional genomics to uncover novel genes and pathways involved in plastic biodegradation. Our findings not only advance the understanding of PU degradation but also open new avenues for developing innovative solutions for plastic waste management.