Self‐Assembled Living Microreactors for Selective Microcystin Removal via Cascade Sieving, Adsorption and Biodegradation

Microcystin contamination caused by harmful cyanobacterial blooms is a growing global challenge for water safety. Here we reported a self-assembled living microreactor that encapsulated microcystin-degrading bacteria within a biochar-reinforced double-network hydrogel, enabling integrated molecular sieving, adsorption, and enzymatic degradation. The system exhibited size- and charge-selective removal of microcystin over coexisting organic matters, while maintaining high degradation efficiency under harsh stress conditions, including pH (5-9), inorganic ions (10-200 mg/L), and natural organic matters (5-20 mg/L). The microreactor demonstrated excellent mechanical stability, negligible cell leakage, and high bioactivity, and achieved nearly complete removal of microcystin-LR during five repeated operation cycles and continuous biofiltration in environmental water, confirming its scalable application potential. Mechanistic investigations revealed a cascade process involving shell-confined molecular sieving, adsorption-mediated toxin enrichment on biochar, and localized biodegradation within the living core. This work establishes a generalizable design paradigm for programmable living materials, offering new opportunities for selective biodegradation and remediation in complex aqueous systems.