Synthetic biology approaches for the valorisation of waste streams

Abstract

Waste pollution and linear economic models have long caused detrimental environmental effects upon our planet. Modern society now faces breaking points in the climate crisis, human-health, biodiversity loss and depletion of natural resources. While efforts to mitigate waste pollution are essential, waste generation is intrinsically tied to our global development. But if we can provide solutions to work alongside it, waste does not have to persist as a predicament for the modern world. Biological valorisation can provide such a solution, whereby waste can be used as a low-cost renewable feedstock to produce high-value compounds and materials. To realise this ambition, we must develop robust biocatalytic and metabolic processes with the necessary capabilities to deal with the highly heterogenous and complex nature of waste, all whilst being able to attain viable bioproduction. The work described in this thesis presents the development of biological processes and tools to help fulfil this ambition. First, a novel advanced biorefinery process is presented that utilises municipal solid waste as a feedstock for bioproduction of biopolymers and biotherapeutics. Careful selection and engineering of Pseudomonas putida enabled efficient co-utilisation of complex, heterogenous substrate compositions derived from the enzymatic pre-treatment of the most abundant municipal solid waste fractions. The range of products that can be obtained through the process can thus be adapted to enable the conversion of mixed waste to tailor specially chemicals. Limitations still however exist before achieving the cost-effective implementation of waste biorefineries, including those associated with its biodegradation. Further engineering efforts will thus necessitate the development of robust and tailored synthetic biology tools. The next project presented here describes a framework for the systematic development of genetically encoded biosensors with tailored sensing performances. This method provided a series of plastic monomer biosensors with varied performances, and their application in the discovery of novel plastic degradation enzymes is readily envisioned. Lastly, this project demonstrates the potential bioremediation and valorisation of model waste associated organohalide pollutants in P. putida, describing simple routes for their valorisation. Together, this thesis describes a starting point to the development of biological processes and tools towards complex waste valorisation. It is hoped that this thesis will inspire new works towards the increased adoption of circular waste bioprocesses.

Date of Award	31 Dec 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Nicholas Turner (Supervisor), David Leys (Supervisor) & Neil Dixon (Supervisor)