Polysulfone-reinforced quorum quenching media with silica cage encapsulation: Advancing biofouling control in anaerobic membrane bioreactors

Microbial quorum quenching (QQ) using live QQ cells entrapped in a hydrophilic polymer network (e.g., hydrogel) reduces membrane biofouling but encounters challenges regarding mechanical robustness and long-term stability. This study addresses this limitation by developing a novel composite biomedium that encapsulates QQ cells (Rhodococcus sp. BH4) within porous silica cages, which act as a protective barrier against solvent exposure, and further reinforces the structure with polysulfone, a thermally and chemically stable polymer. Surface observations confirmed the successful encapsulation of the cells within the silica matrices. Further analyses revealed the distinct nature of the composite media composed of QQ bacteria, silica, and polymer networks with an amorphous structure essential for flexibility and cell viability. The mechanical properties of the polysulfone-reinforced biomedia were significantly improved, with tensile strength nearly four times higher than that of the conventional hydrogel-based biomedia, making the new media far more durable for long-term applications. When exposed directly to the solvent dimethylacetamide, unprotected BH4 cells experienced severe death and inactivation; however, encapsulation in the porous silica cages maintained 70% cell viability and 77% QQ activity, demonstrating the protective efficacy of the silica matrix. In anaerobic membrane bioreactor applications, the reinforced QQ media showed remarkable biofouling mitigation, extending operational times by approximately threefold and twofold compared to reactors with no media and vacant media, respectively. Using composite QQ media led to significant reductions in the concentrations of biopolymers and quorum-sensing signal molecules, contributing to prolonged membrane service times without negatively impacting overall treatment performance. These findings represent a significant advancement in developing QQ media for antifouling, sustaining the functionality of live QQ cells within durable polymer matrices.