iGEM Athens 2024: e-PHAESTUS
The use of electronic and electrical equipment (EEE) is steadily expanding, resulting in an e-waste management dilemma. Every year, enormous quantities of electronics containing valuable and hazardous materials are incorrectly disposed of. In 2019, an estimated 53.6 million tonnes of e-waste were generated worldwide, with only 17.4% correctly recycled.
According to official data from the European Commission, this issue is particularly serious in our country, Greece. Almost all e-waste is burnt or discarded in landfills, spewing dangerous compounds to both the environment and humans. Furthermore, the precious metals present in e-waste, such as gold, silver, and copper, are not retrieved or utilized, causing a negative impact on the national economy.
In response to this complex challenge, the iGEM Athens 2024 team presents e-PHAESTUS, a biomanufacturing/bioremediation project that involves the bioleaching of e-waste. The project is greatly influenced by the god Hephaestus and our region's mining heritage. Our team focuses specifically on the tripeptide Glutathione. Glutathione (GSH), is a tripeptide that contains -SH and -COOH groups, binds to and solubilizes metals. Using synthetic biology, our team hopes to genetically modify the bacteria E.coli and significantly increase GSH production.
From ancient times and through millennia of human history up to the present day, we have progressed and developed our human civilization through the forging of metals, creating all sorts of wonderful devices.
Electronic and electrical devices are, perhaps, the pinnacle of this long civilizational history, yet, like everything else, they do not last forever. When their life-cycle ends, they become e-waste. So, as we hope to bring e-waste recycling and metal upcycling to a new era, we looked for inspiration in our past:
In ancient Greek mythology Hephaestus is the god of the forge, who used his hammer to make the weapons of Heroes and Olympians alike. He bent the metal to his will and crafted wonderful things. In the same way, we hope to use the “hammer” of synthetic biology to breathe new life into old electronic and electrical devices. Our hammer, of course, is not made of iron, but of DNA.
These ideas are what brought e-PHAESTUS to life, the name being a wordplay of the name of the ancient god, starting with the famous “e-” which has come to characterize all things electronic. For our logo, we chose the Hephaestus himself, holding his hammer, with the DNA replacing the handle symbolizing synthetic biology. The illustration of the logo was done in order to invoke the iconic style of 90’s video game graphics.
Today, more and more human activities depend on electronic devices. From remote work to health and fitness tracking, we have ingrained these devices in our daily lives. But, nothing lasts forever, and eventually all of these devices will complete their life-cycle. These old electric and electronic devices are called e-waste and they are a major concern.
According to the United Nations (Global E-Waste Monitor 2024) the amount of e-waste produced each year stands at around 62 billion kg, amounting to almost 8 kg per capita. Out of this 62 billion kg, only 13.8 are collected and recycled, leaving almost 49 billion kg that are still handled in fundamentally unsound ways.
The e-waste produced each year contains 31 billion kg of metals, most of which are completely lost in landfills. These metals have a dual character. On the one hand, some of them can be extremely polluting to the surrounding environment causing immense ecological damage. On the other, they have significant value given their wide-ranging applications.
In addition, of the e-waste that is indeed recycled, most of it is not recycled in environmentally sustainable ways. The methods currently used for e-waste recycling are Pyrometallurgy (recycling of metals through melting point separation) and Hydrometallurgy (recycling of metals through chemical reactions) suffer from the creation of their own toxic byproducts and their high needs for either energy or chemical compounds. As such, a truly new approach needs to be developed.
(This is a general description. For more detailed description, please refer to the Design and Engineering pages)
Taking all of those considerations into account, we started looking far and wide for possible solutions to this problem. We spent months examining relevant bibliography seeking to understand all the potential solutions and see which one would fit us best.
Any solution involving synthetic biology is based on the idea of bioleaching, which can be defined as the use of microorganisms (or the products of microorganisms) for the dissolution of metals. This dissolution is key as it frees metals from the electronic components they used to compose. There are several different approaches to bioleaching, each with unique pros and cons.
After much research, we settled on a system based on glutathione. Glutathione is a tri-peptide (composed of glycine, cysteine, and glutamic acid) with the unique ability to bind to the metals contained in e-waste and dissolve them. In addition, glutathione can be used to create nanoparticles with the metals it isolates. These nanoparticles are extremely useful in a variety of applications, such as pharmaceuticals. Therefore, our approach does not just recycle e-waste, it upcycles it, creating a truly sustainable future for e-waste.
Glutathione is a known antioxidant and therefore exists in many cell types. Glutathione is usually biosynthesised through 2 reactions. But the enzymes used by most organisms do not produce nearly enough glutathione for our purposes.
Bi-functional glutathione synthetase (GshF) has the unique ability to catalyze both of the previous reactions and allows us to produce far higher quantities of glutathione, enough for the purposes of this project. Nevertheless, GshF consumes 2 ATP molecules of each catalytic cycle. Therefore, in order to create a system that is as autonomous as possible, we also need an enzyme that produces ATP from ADP + poly-phosphate. In our case, we have selected a poly-phosphate kinase (PPK).
The general idea is as so: The genes for the two enzymes are cloned into an expression vector which is then used to transform an appropriate bacterial strain. This strain expresses the enzymes which are then isolated.
Then final contraption would look something like this (for a better understanding of the contraption, please refer to the Hardware Page). We hope to immobilize the isolated enzymes and flow the amino acids through them. The produced glutathione would be guided to the waste
through special valves and filters. This system is designed with the aim to recycle both the amino acids and the ADP and produce as little waste as possible.
Of course, nothing is perfect, and neither is our method. Therefore, we also hope to seek ways to optimize the bioleaching rate and the production of nanoparticles (parts of these efforts can be found in the Model and Software pages).
We, the iGEM Athens 2024 Team, deeply believe in the ideas of recycling and the circular economy, and we hope that this project can be part of the “revolution” required to create a truly sustainable future for e-waste.
As such, we have undertaken an effort to highlight the entrepreneurial aspects of our idea such as the business model, the steps required to bring it to market. We have also been active in educating the general public on e-waste, bringing this matter to the forefront of public discussion. We consider those activities to be a fundamental part of our vision.
Baldé et al, (2024). International Telecommunication Union (ITU) and United Nations Institute for Training and Research (UNITAR). 2024. Global E-waste Monitor 2024. Geneva/Bonn
Chenniappan, Anchana. (2022). Bioleaching of Metals from Printed Circuit Boards. Nature Environment and Pollution Technology. 21. 599-606.
Xing Zhang, Hui Wu, Bing Huang, Zhimin Li, Qin Ye, One-pot synthesis of glutathione by a two-enzyme cascade using a thermophilic ATP regeneration system, Journal of Biotechnology, Volume 241, 2017, Pages 163-169