Poly (ethylene terephthalate) degradation in a novel bacterial strain
Publication Date
July 27, 2026
Creator
Jasmine Leung Cutler
Abstract
Plastic has become a ubiquitous material in modern society and is prized for its versatility, low price and durability. However, although the durability of plastics is one of the great advantages of the material, it has become a serious issue when it comes to end-of-life considerations. Plastic production is increasing every year, and 40% of plastic produced is single use and is almost immediately discarded. The recycling rates of plastics depend on the exact polymer composition, but only around 32% of plastic is recycled in Europe and the recycling rate can be close to zero in countries without the necessary infrastructure in place for waste plastic collection and treatment. Plastic waste which is inappropriately disposed of can enter the environment where it accumulates due to its recalcitrance to degradation. Pollution of the environment by plastic detritus and micro-sized plastic particles has been observed in almost every environment on earth, with the long-term effects of global plastic pollution not yet fully understood. Most plastic is currently produced from unsustainable fossil-based petrochemical sources and the current recycling systems in use are, in general, not fully circular and so the entire system is not sustainable in perpetuity.
One method currently being investigated to combat some of these urgent issues is the potential for use of biological methods for plastic recycling. Multiple enzymes which can degrade various kinds of plastic have been reported along with some bacterial species which can use poly (ethylene terephthalate) (PET) as a sole carbon source.
This thesis involved the evaluation of one such bacterial species- a member of the genus Streptomyces, which was previously shown to be able to use virgin PET as a carbon source for growth. A PET degradation enzyme candidate from this strain named FPETase was further investigated utilising a combination of bioinformatics, gene knockouts and in vitro enzyme assays which showed that the FPETase enzyme was able to degrade bis (2-hydroxyethyl) terephthalate (BHET), a breakdown product of PET. Finally, transcriptomic and proteomic data was used to identify further potential PET degradation enzyme candidates in the strain and a lipase homologue enzyme with a lid domain was identified which was significantly upregulated in the secreted proteome when the strain was growing using PET as the sole carbon source. The strain was also observed to produce a biofilm when exposed to PET plastic powder. This behaviour was further investigated utilising atomic force microscopy and metabolic depth profiling of the biofilm when grown on glass and on PET which showed increased surface roughness in a heterologous pattern when grown on PET but not on glass.
In this work, the original FPETase enzyme was shown to be able to degrade BHET but could not detectably degrade mono(2-hydroxyethyl) terephthalate (MHET) or PET plastic. This enzyme also was not shown to significantly increase in abundance in transcriptomic and secretomic data of growth on the strain on PET. A novel enzyme candidate for PET degradation in the strain was identified from the secretomic data which was determined from bioinformatic analysis to be a lipase homologue. Finally, a novel method was developed to grow the strain on PET and glass surfaces to investigate biofilm formation in the strain in relation to PET degradation and the generated PET biofilm samples were shown to have an increased surface roughness compared to the glass biofilm samples. OrbiSIMS- an instrument combining secondary ion mass spectrometry (SIMS) with the Orbitrap ion trap mass analyser- was also used to investigate the biofilm samples, but there did not appear to be much difference in the metabolite profile of the biofilm on PET and on glass.
Item Type
ethesis
Thesis Type
PhD
Supervisors
University of Nottingham
University of Nottingham
Conradie, Alex
University College London
Subjects (LC)
Associated Schools / Departments
UoN Repository URI
Except where otherwise noted, this item's license is described as
File(s)![Thumbnail Image]()
Name
CUTLER, Jasmine Thesis (hyperlink corrections).pdf
Size
10.71 MB
Format
Adobe PDF
Checksum (MD5)
4ab713319d25c114942ea5ab9ad4516c