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430000000
metric tons of plastic
are produced each year globally
Our planet is covered in plastic! Wildlife and ecosystems are collapsing on a synthetic polymer we designed to make life easier. Every year 430 million tons of mixed plastics are produced. Despite this, only around 9% of worldwide plastic waste has been recycled (d’Ambrières, 2019). The current techniques are designed for single-polymer plastic products like PET bottles or PE bags. However, many products are not only composed of one plastic type or don’t get sorted correctly, resulting in mixed plastic waste. Mixed plastics often end up in landfills or incinerated as they cannot be recycled using current methods. These methods have a substantially high energy demand, greenhouse gas emission, and rely on large scale infrastructure. (Stegmann et al., 2022). New innovative ideas are needed to help combat this growing problem. Bioremediation has recently been introduced as a possible solution. However, most research on this subject still focuses on single-polymer plastic instead of mixed plastic (Sharma, 2018). This is precisely where our approach comes into play!
With ReMixHD, we are creating an innovative biological platform capable of upcycling mixed plastic waste sustainably using genetically modified Pseudomonas fluorescens. We will utilize a co-culture approach with a helper strain responsible for mixed plastic degradation and a main strain that uses its intermediates as a carbon source to produce a recombinant product. ReMixHD aims to create the first plastic degradation regulatory operon. Furthermore, we aim to establish P. fluorescens as a new chassis organism for bioremediation and to design a cutting-edge genome-scale metabolic model allowing for dynamic and co-culture modeling.
We modified two strains of the non-model bacterium Pseudomonas fluorescens to divide the challenges of plastic bioremediation into two parts: A helper strain that depolymerizes PET and PE into their monomers with the help of the respective enzymes FAST-PETase and AlkB. PE can be broken down into alkanes and PET into terephthalic acid (TPA) and ethylene glycol. TPA is metabolized by an engineered main strain that utilizes it as a carbon source for synthesizing any recombinant product. We custom-engineered an operon to control the growth behavior of the helper strain. This division of labor allows for more flexibility in adapting to local needs and increases product yields by lowering the metabolic burden. We used a modified alkane sensor and a terephthalic acid sensor for growth regulation. The alkane sensor leads to the expression of a growth factor predicted by our modeling team. The main strain uses TPA as a carbon source for growth, thereby enabling the unrestricted synthesis of any recombinant products. This mixed bioremediation method offers so many possible applications!
Our system of upcycling mixed plastic using a smart co-culture is sustainable, expandable, and can be tailored to local demands. Depending on the demand and the requirements of plastic waste management, we can add further modified bacterial strains. These strains can be specifically designed to break down more types of plastic and produce new products in the future, making our platform highly adaptable and versatile. Our goal is to generate polyhydroxyalkanoates (PHA), a bioplastic. Using our approach we could synthesize anything from fertilizers to insulin, all through exchanging the main strain used in the co-culture. With these two selectable parts, anyone could individualize the co-culture depending on their needs. This is not just simple recycling. This is a circular economy taken to its logical conclusion!
ReMixHD not only reduces the environmental impact of plastic waste, but also actively supports the goals of the United Nations Sustainable Development Goals. By using innovative technology to create sustainable solutions while minimizing the consumption and waste of plastics, we are helping to shape a sustainable and resilient future for our world.
We considered the broader implications of our project’s impact on the following four SDGs:
SDG 9 - Our biological recycling platform represents an innovative technology that addresses the pressing challenges of mixed plastic waste recycling and strengthens the local waste management infrastructure.
SDG 11 - ReMixHD has the potential to significantly reduce the environmental impact in cities and towns by efficiently and sustainably removing plastic waste. In this way, our project contributes to creating clean and liveable cities.
SDG 12 - Our platform enables the reduction of plastic waste and promotes more sustainable consumption and production patterns by upcycling mixed plastic waste to create new products.
SDG 13 - ReMixHD helps to reduce greenhouse gas emissions and mitigate climate change by upcycling mixed plastics into valuable resources.
Bürstner, V., & Chen, Y. (2023, May). Stakeholder call with Company Interzero. personal.
d’Ambrières, W. (2019). Plastics recycling worldwide: current overview and desirable changes. The Journal of Field Actions, (Special Issue 19), 12–21.
Milà i Canals, L., Cairns, A., Lefort, P., Meso, A., David Raine, A., Smagadi, A., Stone, S., & Tonda, E. (2023). Turning off the Tap - How the world can end plastic pollution and create a circular economy. United Nations Environment. https://wedocs.unep.org/bitstream/handle/20.500.11822/36963/POLSOL.pdf
Sharma, S.R. (2018). Bioremediation of Polythenes and Plastics: A Microbial Approach. In: Prasad, R., Aranda, E. (eds) Approaches in Bioremediation. Nanotechnology in the Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-030-02369-0_6.
Stegmann, P., Daioglou, V., Londo, M., van Vuuren, D. P., & Junginger, M. (2022). Plastic futures and their CO2 emissions. Nature, 612(7939), 272–276. https://doi.org/10.1038/s41586-022-05422-5.
Pinto, M., Zhao, Z., Klun, K., Libowitzky, E., & Herndl, G. J. (2022). Microbial Consortiums of Putative Degraders of Low-Density Polyethylene-Associated Compounds in the Ocean. mSystems, 7(2), e0141521. https://doi.org/10.1128/msystems.01415-21.
