The accumulation of poly(ethylene terephthalate) (PET) plastic waste has become a global pollution concern, motivating the urgent development of technologies to valorize post-consumer PET. The development of chemocatalytic and enzymatic approaches for depolymerizing PET to its corresponding monomers opens up new opportunities for PET upcycling through biological transformation [2]. However, there are only a handful of reports demonstrating non-model microbes capable of growing on both terephthalic acid (TPA) and ethylene glycol (EG) monomers generated from PET as sole carbon sources. Moreover, the scarcity of synthetic biology tools specifically designed for these non-model species limits the development of the corresponding microbial cell factories for upcycling the post-consumer PET. To overcome these limitations, we performed strain screening to discover a
Rhodococcus strain RPET (RPET) that can grow well on the alkaline hydrolysis products of PET as the sole carbon source. Notably, this strain can grow on a mixture of TPA and EG at extremely high concentrations (up to 0.6M) and high osmolarity resulting from alkaline hydrolysis and pH neutralization. The resultant media supported RPET’s growth without any purification and sterilization steps except for their dilution [1]. To expand the repertoire of bioproducts from post-consumer PET, we have developed genetic tools in RPET. Using these tools, we engineered the RPET strain to ultimately establish microbial supply chains of multiple chemicals, producing the highest titers of chemicals ever reported thus far, including lycopene, lipids, and succinate, from post-consumer PET waste bottles (e.g., 22.6 mg/L of lycopene, about 10,000-fold higher than that of the wild-type strain). This work highlights the great potential of plastic upcycling as a generalizable means of sustainable production of diverse chemicals [2]. Additionally, our engineered microbe’s application for space exploration has been demonstrated, for which three alternative feedstocks, including Martian and Lunar regolith, post-consumer PET, and fecal waste, have been developed, optimized, and used to produce lycopene under a microgravity condition [3]. We will discuss the future of our plastic upcycling technology.
[1] Diao, J., Hu, Y., Tian, Y., Carr, R. & Moon, T.S. (2023). Cell Rep 42, 111908.
[2] Diao, J., Tian Y., Hu Y., Moon, T.S. (2024). Trends Biotechnol 43, 620-646
[3] Lee et. al. Nature Communications (2025) 16, 728
