Synthetic Biofilms for Green Membranes: Engineering Low-Energy Filtration Systems

Membrane filtration is a key technology to modern water purification, yet its sustainability is compromised by biofouling, which increases energy consumption and ecological impacts. Conventional control strategies often struggle to balance efficacy and environmental footprint. In this study, an inducible, engineered quorum-quenching (QQ) bacterium was constructed via a genomic integration strategy, thereby achieving control over the biofilm structure in membrane filtration biofouling layers. By using the clustered regularly interspaced short palindromic repeat (CRISPR-Cas) targeted gene editing technology, the engineered bacteria that were constructed to express aiiO under l-ribose induction have achieved the regulation of biofilms. Validation using a gravity-driven membrane ultrafiltration system (UF-GDM) model showed that the engineered bacterium effectively reduced extracellular polymeric substances (EPS) components, increased the hydrophilic porosity of the residual biofilm, and decreased its stickiness. This approach reduced transmembrane pressure by 64.5%, increased total organic carbon (TOC) removal by 13.2%, and extended membrane lifespan by 16.1%. A technical-economic analysis indicates that the 100,000 m³/day treatment plant achieves an annual net profit increase of 31.52%, reaching 1.55 × 10⁷ CNY, while reducing its net carbon footprint by 27.43%, with an annual net reduction of 2.96 × 10⁵ kg CO₂eq. This study provides a novel solution strategy for achieving biofouling resistance and sustainable, low-energy operation in membrane filtration processes, which contributes to the broader application and adoption of this technology.