Nature-inspired Circular Recycling for Polymers

Objective

In 2070, 10^12 Kg of plastics (polymers) could be produced yearly in a world inhabited by 11 billion people. Hence, we have ~50 years to address this sustainability challenge. The sourcing and disposing of such quantities without a significant environmental impact will not be possible, even if everything is bio-sourced and bio-degraded. Yet, on earth, there are >10^12 Kg of proteins (one of Nature’s polymers). They are sustainable because they are recycled in a circular way. If we exemplify their metabolism, proteins are decomposed by living organisms into their monomeric constituents (the amino acids, AAs); the cell machinery uses such AAs to synthesize new proteins that have little in common with the original ones. This is only possible because a protein is a specific sequence of AAs bound together by cleavable peptide bonds, i.e. proteins are sequence-defined polymers, SDPs. Nature reuses and does not degrade AAs, thus assuring protein sustainability. This project aims at showing that such a circular approach to recycle SDPs is possible for technologically-relevant polymers using engineering-sound laboratory processes. One aim is to show that b-Lactoglobulin, a milk protein used as a component for water filtration membranes, can be digested into its AAs, that, in turn, can be used to form Fibroin, a silk protein used in resistive switching memory devices. Fibroin will be converted into Keratin, a wool protein, that will be converted back into b-Lactoglobulin. Another aim is to perform the whole process within an automated and scalable robotic platform. The final aim is to expand this concept from natural proteins to DNA and non-natural SDPs. There would be a paradigm shift in plastic recycling, if a random mixture of any polymers could be used to produce any other polymer on earth, without taxing the planet with degradation products. Scope of this project is to show that such a vision in the circular use of polymers is scientifically and technologically possible.