Optimizing UV-B induced prophage activation for restructuring microbial aggregates and Suppressing recolonization in membrane filtration systems

Membrane biofouling remains a persistent challenge in membrane filtration systems. Although phage-mediated lysis has emerged as a promising biocontrol strategy, its effectiveness can be limited by the structural protection of microbial aggregates and hydraulic conditions. Herein, we investigated targeted UV-induced prophage activation and the resulting ecological dynamics between host and non-host bacteria within lab-scale membrane filtration platforms by using E. coli phage-host system. The optimized parameters of UV-induced prophage activation under 313 nm UV-B irradiation were set at low energy of 4.6 mW/cm², with E. coli phage progeny reaching 1.9 × 10⁴ PFU/mL after 2 min treatment. Transcriptome analysis showed the 1.2-fold up-regulation of bacterial redox-regulator genes (soxRS) and down-regulation of biofilm formation genes (csgC, pgaB), indicating a cellular stress response associated with prophage activation. Subsequent recolonization experiments showed altered contributions of host and non-host invasive populations (AS, 34 %), reduced microbial diversity (28 %), and restructuring of membrane-associated microbial aggregates. An experimentally informed Susceptible-Carried-Infected-Lysed (SCIL) model further reproduced the observed trends in host suppression and phage production under UV-induced stress. Moreover, in cross-flow filtration system, prophage activation was accompanied by restructuring of the extracellular polymeric substance (EPS) matrix, with a 55 % decrease in the protein-to-polysaccharide (PN/PS) ratio and a 31.4 % reduction in aggregate thickness, together with delayed transmembrane pressure (TMP) development. These results demonstrate that controlled UV-B-induced prophage activation can act as a phage-mediated ecological disturbance that restructures resident biofilms and alters subsequent microbial recolonization, providing ecological insights and theoretical guidance for future biofouling-control strategies in wastewater membrane filtration.