About This Project

The increasing production of Polyethylene terephthalate (PET) combined with inadequate waste management and a lack of effective recycling technologies has led to the accumulation of PET material and significant environmental pollution. Biocatalysis is a promising but yet inefficient solution to address the recycling or up-cycling of PET in an environmentally friendly and cost-effective manner. Here an assay platform is developed to support the improvement of PET biocatalysts.

Ask the Scientists

What is the context of this research?

Petroleum-based plastics are forecast to consume 20% of global petroleum and contribute 15% of greenhouse gas (GHG) emissions by 2050 [1, 2].

At 82 million metric tons/year, polyethylene terephthalate (PET) is the most produced synthetic polyester globally. Recycling struggles to match virgin plastic quality and economics, leading to crude oil reliance for precursor production which causes 76% of PET's GHG emissions (2.4 kg CO2e/kg of PET) [3, 4]. PET waste management strategies today also contribute significantly to GHG emissions as well as to the release of toxic chemicals leading to water and soil contamination [5].

Additionally, uncontrolled plastic accumulation threatens ecosystems, wildlife and enters the food chain, with unknown health consequences [6].

What is the significance of this project?

PET hydrolyzing enzymes (PHEs) can reduce PET's environmental impact by up to 95%, offering an eco-friendly waste management solution that economically outcompetes virgin plastic production and reduces reliance on crude oil. However, the practical use of PHEs is hindered by their low efficiency. Beyond the insufficient natural evolution for PET hydrolysis, the limitation of lab experiments to low throughput methods hampers both the mechanistic understanding and the artificial enhancement of PHEs [9,10,11,12]. Currently, 3 kg of enzyme is needed to hydrolyze 1 ton of PET[13], making it unfeasible to scale up PHE production to meet global PET recycling demands. To succeed, more efficient and stable PHEs are needed, requiring a breakthrough in our ability to screen, evolve, and engineer them.

What are the goals of the project?

A critical step in developing more efficient PHEs is assaying their activity, a process which is currently low-throughput, time-consuming and expensive. Thus, the first goal is to develop an assay platform for PHE activity that is ultra-high throughput (>10^5 fold higher than status quo), cheap and reliable, by utilising a cell-based biosensor to detect PET hydrolysis products. The second goal is to utilise this new platform to evolve known PHEs, whilst also collecting large-scale datasets that can be used for the discovery of novel PHEs through homology-based searches and to train machine learning models to efficiently enhance the activity and stability of known PHEs. Ultimately this would lead to the final goal of delivering enzymes which can facilitate a circular PET economy.