Polyethylene is the most widely used plastic and arguably one of the most versatile materials to ever be synthesized. Its practicality and convenience however, have come at a great environmental cost. Polyethylene takes millennia to decompose, leaching harmful microplastics into the environment. We approached this pressing issue from a synthetic biology perspective, making use of E. coli engineered with genes encoding for laccase to degrade polyethylene into smaller alkane chains. Our team recognizes the opportunity to further advance this project by addressing another key issue – energy. Using Shewanella oneidensis MR-1 strain’s inbuilt extracellular electron transport mechanism in tandem with genes responsible for alkane metabolism derived from Desulfatibacillum alkenivorans, we will generate electricity from the metabolism of degraded polyethylene, hoping that it will one day help in solving the world’s growing energy needs. Thus, our project serves as an integrated effort to simultaneously solve two crucial problems.
To achieve our goal of electricity generation from plastic degradation, we separated our project into three independent but interconnected modules. The first stage, the PE degradation module, focused on creating a genetic construct that would readily synthesize and secrete Laccase in order to degrade the polyethylene into smaller alkanes. Once fragmented, the alkanes would be processed by our second stage - the alkane metabolism module. This module plans to introduce alkane uptake and metabolism pathways into Shewanella oneidensis MR-1 so that it can process alkanes and channel the electrons obtained from its cellular respiration. The third and final module was the physical construct of the microbial fuel cell. We housed the Shewanella within a microbial fuel cell of our design to characterise and optimise the electricity generated. The following is a schematic to describe the flow of the project.