21ENGBIO: Engineering Biology for Integration with Deep Eutectic Solvents

Deep eutectic solvents, especially the bio-based ones being used within this work, are 'green solvents' with low toxicity and sustainable sources. They can be used in a wide variety of processes ranging from the valorisation of food waste, to drug delivery systems. In this work we will be using deep eutectic solvents that have been used to semi-selectively recover metals from green technologies, such as electric vehicle batteries. We will examine the potential for these deep eutectic solvents laden with dissolved metals to be used as a feed for bacteria that produce metal nanoparticles and optimise the process accordingly by engineering the bacteria. Our aim is to be able to recover the metals, especially those that are categorised as 'critical materials', from green technologies that have come to their end of life, so that the metals can be used again, and to do so in process that is sustainable, low energy and environmentally safe.

Deep eutectic solvents (DESs), especially the biocompatible type III eutectics being used within this work, are 'green solvents' with low toxicity and sustainable sources. They are used commercially in a wide variety of processes including the valorisation of food waste, drug delivery systems, metal extraction and land remediation. Their use therefore touches on all application-inspired themes and challenges identified as future opportunities for the National Engineering Biology Programme (Biomedicine, Clean Growth, Food systems and Environmental Solutions).
In this proof of concept work we will use DESs that have been used to semi-selectively extract metals from end of life green technologies, such as vehicular lithium ion batteries batteries. We will engineer nanoparticle-synthesising bacteria to use these DES leachates as a growth medium and selectively precipitate the metals they contain for recovery and future use. This therefore offers a sustainable, low energy and environmentally safe production process for nanoparticles and novel materials, that also recovers critical metals from the green technologies that are vital to global ambitions for achieving net-zero and a circular economy.