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| Home > Publications database > Biodegradation and microbial upcycling of plastics |
| Book/Dissertation / PhD Thesis | FZJ-2024-05892 |
2024
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-804-9
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Please use a persistent id in citations: urn:nbn:de:0001-2503060801542.370078637444 doi:10.34734/FZJ-2024-05892
Abstract: Plastics have undoubtedly revolutionized our daily lives, becoming irreplaceable in several sectors, including packaging, healthcare, and automotive industries. However, current endof- life strategies cannot cope with the increasing global production, which exceeded 400 million tons in 2022, leading to a global plastic pollution crisis. Biological catalysis has the potential to overcome the drawbacks of conventional recycling, using enzymes and microbes for the depolymerization of plastics and their subsequent conversion to value-added compounds. To facilitate the transition towards a circular plastics economy, the overall goal of this thesis is to provide new biological end-of-life solutions for plastics. Therefore, the substrate range of the biotechnological workhorse Pseudomonas putida KT2440 was expanded with prevalent plastic hydrolysates providing them as feedstock for microbial upcycling. Deep metabolic engineering enabled the utilization of polyamide (PA) hydrolysates as a carbon source, while RNA-sequencing revealed the synthetic metabolic routes and how they mesh with the native metabolism. In parallel, new nylonase enzymes were discovered and characterized that showed activities towards PA and poly(esteramides). In addition to PA-derived compounds, metabolic routes for dicarboxylic acids and diols were established and their combination yielded a powerful platform strain that fully metabolized a complex polyester mock hydrolysate. Moreover, rational metabolic design enabled the degradation of branched short-chain dicarboxylates, including itaconic acid, thereby further expanding the metabolic palette of Pseudomonas with plastic monomers. To close the life cycle of plastic waste, hydrolysates should not only be metabolized but also upcycled. This was achieved by converting the newly accessible plastic-derived feedstocks into polyhydroxyalkanoates, demonstrating, among others, the conversion of nylon to polyhydroxybutyrate through hydrolysis and microbial conversion. The resulting products are environmentally benign due to their biodegradability and resources are maintained in the material cycle, reducing the production of virgin fossil-based plastics. With regard to a circular plastics economy, it is essential to consider plastic coatings as an additional source of complexity in plastic waste. For this, the novel Halopseudomonas formosensis FZJ was isolated from a compost heap due to its ability to metabolize poly(ester-urethane) coatings. The detailed characterization of its metabolic pathways and enzymes provides the scientific basis for future bio-recycling processes of coated plastics and thus increasingly complex materials.
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