Enhancing biofilm formation in the hydrogen-based membrane biofilm reactor through bacterial Acyl-homoserine lactones

The slow growth rate of autotrophic bacteria and regulation of biofilm thickness are critical factors that limit the development of a hydrogen-based membrane biofilm reactor (H₂-MBfR). The acyl-homoserine lactone (AHL) mediated quorum sensing (QS) system is a crucial mechanism regulating biofilm behavior. However, the AHLs that promote biofilm formation in autotrophic denitrification systems and their underlying mechanisms, remain unclear. This study explored the impact of AHL-mediated QS signaling molecules on biofilm development in H₂-MBfR. This study revealed that C₁₄-HSL and C₄-HSL are potential signaling molecules that enhanced biofilm formation in long-term stable operating H₂-MBfR. Subsequent short-term experiments with C₁₄-HSL and C₄-HSL confirmed their ability to increase bacterial adhesion to carrier surfaces by promoting the production of extracellular polymeric substances (EPS). Functional gene annotation indicated that exogenous C₁₄-HSL and C₄-HSL increased the abundance of signal transduction (increased by 0.250%–0.375%), strengthening the inter bacterial QS response while enhancing cell motility (increased by 0.24% and 0.21%, respectively) and biological adhesion (increased by 0.044% and 0.020%, respectively), thereby accelerating the initial bacterial attachment to hollow fiber membranes and facilitating biofilm development. These findings contribute to the understanding of microbial community interactions in H₂-MBfRs and provide novel approaches for biofilm management in wastewater treatment systems.