Polystyrene Upcycling into Fungal Natural Products and a Biocontrol Agent

Polystyrene (PS) is one of the most used yet infrequently recycled plastics. Although manufactured on the scale of 300 million tons per year globally, current approaches toward PS degradation are energy-and carbon-inefficient, slow, and/or limited in the value that they reclaim. We recently reported a scalable process to degrade post-consumer polyethylene-containing waste streams into carboxylic diacids. Engineered fungal strains then upgrade these diacids biosynthetically to synthesize pharmacologically active secondary metabolites. Herein, we apply a similar reaction to rapidly convert PS to benzoic acid in high yield. Engineered strains of the filamentous fungus Aspergillus nidulans then biosynthetically upgrade PS-derived crude benzoic acid to the structurally diverse secondary metabolites ergothioneine, pleuromutilin, and mutilin. Further, we expand the catalog of plastic-derived products to include spores of the industrially relevant biocontrol agent Aspergillus flavus Af36 from crude PS-derived benzoic acid.

Automated summary

Polystyrene (PS) is a commonly used plastic that is not frequently recycled. In this study, a scalable process was developed to convert PS into benzoic acid, which can then be biosynthetically upgraded into various secondary metabolites by engineered strains of the fungus Aspergillus nidulans. This approach expands the range of plastic-derived products and demonstrates the potential for utilizing PS waste in the production of valuable compounds.