The metabolic potential of plastics as biotechnological carbon sources-Review and targets for the future

The plastic crisis requires drastic measures, especially for the plastics' end-of-life. Mixed plastic fractions are currently difficult to recycle, but microbial metabolism might open new pathways. With new technologies for degradation of plastics to oligo- and monomers, these carbon sources can be used in biotechnology for the upcycling of plastic waste to valuable products, such as bioplastics and biosurfactants. We briefly summarize well-known monomer degradation pathways and computed their theoretical yields for industrially interesting products. With this information in hand, we calculated replacement scenarios of existing fossil-based synthesis routes for the same products. Thereby, we highlight fossil-based products for which plastic monomers might be attractive alternative carbon sources. Notably, not the highest yield of product on substrate of the biochemical route, but rather the (in-)efficiency of the petrochemical routes (i.e., carbon, energy use) determines the potential of biochemical plastic upcycling. Our results might serve as a guide for future metabolic engineering efforts towards a sustainable plastic economy.

Automated summary

The plastic crisis demands drastic measures, especially for the end-of-life of plastics. Microbial metabolism offers new possibilities for the recycling of mixed plastic fractions. By degrading plastics into oligo- and monomers, these carbon sources can be utilized in biotechnology to transform plastic waste into valuable products like bioplastics and biosurfactants. The study presents well-known monomer degradation pathways and calculates the potential replacement scenarios for existing fossil-based synthesis routes. The findings highlight the attractiveness of plastic monomers as alternative carbon sources for fossil-based products.