Student project turns landfill waste into bioplastic

The iGEM competition, which is a synthetic biology competition, involves giving student teams a kit of biological parts at the beginning of the summer from the Registry of Standard Biological Parts. Working at their own schools over the summer, they use these parts and new parts of their own design, competing to develop microscopic devices that can be used to help the environment, advance health and medicine, improve IT and make food and energy production more sustainable. The teams make their devices from harmless bacteria and cells such as yeast, re-engineering their DNA to perform pre-determined functions.

The Imperial team re-engineered the genetic code of harmless E.coli bacteria so that they can break down landfill waste and turn it into the bioplastic known as poly-3-hydroxybutyric acid, or P(3HB), which is produced as an energy store in some bacteria. Commercially it is produced in bioreactors from sucrose and other sugars derived from plant biomass. P3HB is industrially biodegradable, breaking down without release of toxic products or intermediates. It has low water solubility, medium-low water and CO2 permeability and very good barrier properties that are ideal for packaging. This biopolymer is easily processable, has a high degree of crystallinity, high melting temperature, and good tensile strength. Its impact strength can be significantly improved with nanofillers.

The team says their process could be scaled up to industrial levels and that using waste material instead of plants could free up agricultural land so that it can be used more productively for agriculture.

Imperial team member Jemma Pilcher said: "In the future, our system could provide a sustainable way to make an environmentally friendly alternative to petroleum-based plastics, which would reduce our dependency on oil. Additionally, this system would divert rubbish away from landfill sites and incinerators, which have very negative effects on the environment by releasing toxins, and instead use it as a resource."

The system is designed to maximize the recovery of resources from the waste. For this reason, wrote the team, "We have also investigated how we can use the oil-based plastics within it to produce the commodity chemical ethylene glycol. We are passionate about using synthetic biology to help us move towards a more sustainable economy."

Next to developing the process to make the material, the students went on to develop the first synthetic biology recycling system for P(3HB) and one of the first in the world. Called Plastic Fantastic, it is a complete P(3HB) bioplastic recycling platform, where P(3HB) is degraded into monomeric form and then re-polymerised back into de novo P(3HB) for future applications.