Engineering Novel Microbes for Upcycling Waste Plastic
Jinjin Diao* (email@example.com), Yuxin Tian, Yifeng Hu, and Tae Seok Moon
Washington University–St. Louis
The goal is to develop a consolidated biological process to upcycle waste polyethylene terephthalate.
Polyethylene terephthalate (PET) represents 12% of global solid waste. PET chemical recycling has been an option to solve this global problem, but it suffers from its relatively high process cost and the extremely low price of virgin PET (~$1/kg). One solution to address this issue is to upcycle waste PET rather than recycle it to generate the same PET typically with low quality. PET upcycling can be achieved by depolymerizing PET into terephthalic acid (TPA) and ethylene glycol (EG) and biologically converting these monomers into value-added products. However, there are only a handful of reports demonstrating microbes capable of growing on both TPA and EG generated from PET as sole carbon sources. To overcome this limitation, researchers have performed strain screening to discover a Rhodococcus strain RPET that can grow well on the alkaline hydrolysis products of PET as the sole carbon source without any purification step. 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 step except for their dilution. In addition, many synthetic biology tools, developed for a related species Rhodococcus opacus (DeLorenzo et al. 2018; DeLorenzo et al. 2021; Diao, Carr, and Moon 2022), were functional in RPET, facilitating its metabolic engineering. In this presentation, researchers discuss the effort to develop this novel chassis for waste PET valorization with PET conversion into carotenoids (up to $7,500/kg) as a proof-of-concept demonstration (Moon et al. 2022). Specifically, researchers discuss lycopene production up to 1.3 mg/L from PET using this technology (Diao et al. 2023). Along with other efforts (Moon 2022), this technology can solve global plastic pollution issues and sustainable chemical production problems.
DeLorenzo, D. M., et al. 2018. “Molecular Toolkit for Gene Expression Control and Genome Modification in Rhodococcus opacus PD630.” ACS Synthetic Biology 7(2), 727–38.
DeLorenzo, D. M., et al. 2021. “An Improved CRISPR Interference Tool to Engineer Rhodococcus opacus.” ACS Synthetic Biology 10(4), 786–98.
Diao, J., Carr, and T. S. Moon 2022. “Deciphering the Metabolic and Regulatory Networks of Aromatic Catabolism using Synthetic Biology Tools.” Communications Biology 5, 1109.
Moon, T. S., et 2022. PCT Patent Application.
Diao, J., et al. 2023. “Upcycling of Poly(ethylene terephthalate) to Produce High-Value Bioproducts. Cell Reports 42, 111908.
Moon, T. S., 2022. “SynMADE: Synthetic Microbiota Across Diverse Ecosystems.” Trends in Biotechnology 40, 1405–14.
This research was supported by the DOE Office of Science, Office of Biological and Environmental Research (BER), grant no. DE-SC0022003.