Lactone-derived biostimulants enhance QQ-mediated biofouling mitigation in membrane bioreactors.

Quorum quenching (QQ) is regarded as an effective strategy for mitigating membrane biofouling in membrane bioreactors (MBRs), as it can disrupt quorum sensing (QS)-mediated biofilm formation-a key contributor to biofouling. QQ bacteria achieve this by degrading QS molecules, typically N-acylated homoserine lactones (AHLs), thereby neutralizing the QS process. The potential to enhance QQ-based biofouling mitigation through biostimulants is promising but remains underexplored. This study investigated the effects of four potential biostimulants - γ-caprolactone (GCL), γ-heptalactone (GHL), 6-caprolactone, and acetanilide - on the QQ bacterial strain Stentrophomonas Y6 in an MBR system. Among the tested compounds, GCL (10 mg/L) and GHL (20 mg/L) significantly stimulated strain Y6, enhancing its ability to reduce the bioreactor's transmembrane pressure (TMP) from 30 kPa to an average of 13 kPa. In contrast, 6-caprolactone and acetanilide showed no noticeable effect on Y6. The observed biostimulatory effects of GCL and GHL may be attributed to their ring structures, which resemble those of AHLs and are absent in 6-caprolactone and acetanilide. These findings provide valuable insights into the application of QQ bacteria and biostimulants in MBR systems to combat membrane biofouling.