Plastic waste is omnipresent in the biosphere and has become an overwhelming environmental concern. Only a small fraction of plastics is recycled or processed when reaching their end of life. A potential solution is the use of microbial activities to transform plastic polymers into other molecules of value. While there has been some success using the plastic polymer polyethylene terephthalate (PET) as a microbial feedstock, there are no equivalent solutions for polyethylene (PE), which is the most widely produced plastic and has very low recycling rates. In this project we will investigate the biodegradation of PE by a novel strain of Stenotrophomonas that can use the polymer as a sole carbon source. We will characterise the biochemical processes involved in the mineralisation of the polymer and its potential for the bioconversion into molecules of added value.
We have investigated the potential of soil microorganisms for the degradation of PE. To this end we have conducted enrichments of soil samples using a commercial PE powder. These powders are representative of the environmental abiotic degradation of films, and their lower average molecular weight compared to films makes them easier to assimilate by microorganisms. We observed microbial growth when using PE as growth substrate in minimal medium inoculated with 0.5 g of soil and enriched microorganisms were isolated and subjected to 16S rDNA sequencing which resulted in the identification of species belonging to the genus. Stenotrophomonas spp. (identified in 10 out of 10 strains analysed after isolation) were taken forward for further analysis. The strains were able to grow on PE powder as sole carbon source when tested individually but not on other plastic polymers.
In this program, our ambition is to use cutting-edge and innovative technologies to explore the ability of new isolates degrading PE as carbon source. We will dissect the ability of the isolates of Stenotrophomonas spp. to metabolize PE and transform it into valuable commodities. The specific aims for this proposal are as follows.
- To identify the metabolic pathways involved in PE mineralisation in Stenotrophomonas sp. In this Workpackage, we will conduct a systematic investigation of activities relevant for the degradation of molecules generated during PE degradation. In preliminary data, we have identified, via TLC and HPLC, a laccase as an enzyme active on PE. We also will produce the chimeric constructs of the relevant Stenotrophomonas enzymes with Plastic Binding Modules (PBM) families identified previously. These PBMs (which are analogous to carbohydrate binding modules, CBMs) have been shown to bind PE, would help laccase to bind to PE, therefore enhancing the activity of selected enzymes. This strategy has been successfully employed to enhance the activity of PET hydrolases. All these constructs will be screened for crystallographic studies to understand their 3D structure.
- To validate the microbial conversion of post-consumer PE and mixed waste.
- To turn Stenotrophomonas sp. into a workhorse for the transformation of PE into molecules with added value.
The successful candidate will have the possibility to be trained at Imperial College London under the Supervision of Dr Jose Jimenez.
Eligibility and How to Apply:
Please note eligibility requirement:
- Academic excellence of the proposed student i.e. 2:1 (or equivalent GPA from non-UK universities [preference for 1st class honours]); or a Masters (preference for Merit or above); or APEL evidence of substantial practitioner achievement.
- Appropriate IELTS score, if required.
- Applicants cannot apply for this funding if currently engaged in Doctoral study at Northumbria or elsewhere.
For further details of how to apply, entry requirements and the application form, see
Please note: All applications must include a covering letter (up to 1000 words maximum) including why you are interested in this PhD, a summary of the relevant experience you can bring to this project and of your understanding of this subject area with relevant references (beyond the information already provided in the advert). Applications that do not include the advert reference (e.g. MRDF22/…) will not be considered.
Deadline for applications: 18 February 2022
Start Date: 1 October 2022
Northumbria University takes pride in, and values, the quality and diversity of our staff and students. We welcome applications from all members of the community.
Informal enquiries to Dr Jose Munoz ([Email Address Removed]).