Bizente gets to the last month of the year with promising developments. Polymers are an indispensable part of our modern life. The chemical structure of today’s polymers, however, also poses an enormous environmental challenge with our plastic wastes accumulating in the biosphere. The reason for this is that today’s polymers have been designed for durability, their chemical structure exhibits few or no functionality enabling spontaneous, physicochemical or biological degradation.

While next generations of polymers will exhibit such handles and therefore enable (bio)degradation of polymer products, our society is still facing enormous amounts of past and present polymer products reaching their end of life. Today, landfilling or ‘thermal valorisation’ (i.e. either burying or burning plastic wastes) still represent the main strategies for dealing with plastic waste streams. An alternative strategy is investigated in the BIZENTE project. Using enzymes, the consortium strives for adding functionality to traditional plastic wastes enabling their depolymerisation. For example, one strategy is to introduce hydroxyl groups next to commonly used ether- or amine bonds in polymers. The resulting products are chemically instable and spontaneously react while breaking the polymer chain.

The reaction not only results in broken chains (degrading the polymer) but also potentially gives access to chemical building blocks, which may be re-used. Hence, the focus of BIZENTE is not only to degrade recalcitrant polymers but also to yield potentially valuable chemicals for further use. As of today, BIZENTE partners have been able to demonstrate the principal feasibility of this approach with low-molecular weight polymer analogues. Peroxygenases have been demonstrated to be enzymes of choice for a simple and environmentally benign degradation of ether- and amine-linkages.

The challenge for future development will lie in the transition to real polymer substrates. The active site of peroxygenases used so far is generally buried within the enzyme itself. However, to make these enzymes active on polymeric substrates, exposure of the enzyme active site to the surface of the enzyme is inevitable. This guiding principle will define future research and development activities within BIZENTE.

Article by TUDELFT