Engineering a microbial ‘trap and release’ mechanism for microplastics removal

Plastics are discarded and accumulated in the environment at an alarming rate. However, their resistance to biodegradation allows them to persist in the environment for prolonged durations. While large plastics are easier to remove, microplastic particles from cosmetics or fragments from larger pieces are extremely difficult to remove from the environment. Furthermore, current techniques such as filters poorly retain microplastics or require harsh chemical treatments in wastewater treatment plants. Hence, microplastics enter the natural environment easily even after effluent treatments, thereby endangering aquatic life and humans who consume seafood. It is imperative to develop sustainable bioaggregation processes to trap microplastics quickly for easier removal from the environment. Here, we showed that microplastics can be trapped and aggregated in the sticky exopolymeric substances (EPS) produced by biofilms. As a proof-of-concept, we engineered a bacterial biofilm with a ‘capture-release mechanism’, whose EPS can first cause bioaggregation of microplastics for easier isolation, followed by an inducible biofilm dispersal mechanism that releases trapped microplastics for downstream resource recovery. We also demonstrated the potential application of the engineered biofilm in mitigating microplastics pollution in seawater samples collected in the vicinity of a sewage outfall. This capture-and-release approach should prove widely applicable to other micropollutants or biofilm-enabled catalysis.