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Biotransformation of ethylene glycol by engineered Escherichia coli
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This study examined the ingestion of tire wear particles by soil-dwelling invertebrates and the resulting ecotoxicological effects. Multiple species ingested tire rubber particles, which caused dose-dependent reductions in growth and survival, indicating that tire wear is a significant and understudied source of microplastic pollution in terrestrial ecosystems.
There has been extensive research on the biological recycling of PET waste to address the issue of plastic waste pollution, with ethylene glycol (EG) being one of the main components recovered from this process. Therefore, finding ways to convert PET monomer EG into high-value products is crucial for effective PET waste recycling. In this study, we successfully engineered Escherichia coli to utilize EG and produce glycolic acid (GA), expecting to facilitate the biological recycling of PET waste. The engineered E. coli, able to utilize 10 g/L EG to produce 1.38 g/L GA within 96 h, was initially constructed. Subsequently, strategies based on overexpression of key enzymes and knock-out of the competing pathways are employed to enhance EG utilization along with GA biosynthesis. An engineered E. coli, characterized by the highest GA production titer and substrate conversion rate, was obtained. The GA titer increased to 5.1 g/L with a yield of 0.75 g/g EG, which is the highest level in the shake flake experiments. Transcriptional level analysis and metabolomic analysis were then conducted, revealing that overexpression of key enzymes and knock-out of the competing pathways improved the metabolic flow in the EG utilization. The improved metabolic flow also leads to accelerated synthesis and metabolism of amino acids.
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This study engineered the bacterium Escherichia coli to break down terephthalic acid — one of the two building blocks released when PET plastic is depolymerized — and use it as a carbon source for growth. By introducing a transporter and enzyme cascade, and then applying adaptive laboratory evolution, the team achieved efficient bacterial growth on terephthalic acid alone. This work is relevant to microplastics because it advances biological PET recycling pathways that could divert plastic waste from the environment before it breaks down into microplastics.
Towards Synthetic PETtrophy: Engineering Pseudomonas putida for concurrent polyethylene terephthalate (PET) monomer metabolism and PET hydrolase expression
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Researchers engineered the bacterium Pseudomonas putida to simultaneously break down PET plastic monomers and express a PET hydrolase enzyme, enabling one-step PET degradation and growth. The engineered strain successfully metabolized both TPA and EG monomers released during PET hydrolysis. This work advances the development of microbial biocatalysts for plastic recycling and upcycling.
Metabolic and enzymatic engineering strategies for polyethylene terephthalate degradation and valorization
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Researchers reviewed metabolic and enzymatic engineering strategies for breaking down PET plastic waste, highlighting advances in engineered PETase enzymes and microbial pathways that could enable cost-effective biological recycling of the roughly 29 million metric tons of PET produced annually.
Increased cytoplasmic expression of PETase enzymes in E. coli.
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Researchers optimized the production of PETase — an enzyme that breaks down PET plastic — in E. coli bacteria, achieving higher yields of active enzyme using a bioreactor. Improving enzyme production methods is a key step toward scaling up biological plastic recycling to address PET pollution in the environment.
Laboratory evolution reveals the metabolic and regulatory basis of ethylene glycol metabolism by Pseudomonas putida KT2440
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Researchers used adaptive laboratory evolution to unlock ethylene glycol metabolism in Pseudomonas putida KT2440, revealing that mutations in the transcriptional regulator GclR and two accessory genes are required for this plastic-associated pollutant to serve as a sole carbon source.
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